Sensation and Perception

Unit IV Sensation and Perception

PD Unit Overview We rely on our senses to understand the world around us. The sense • Discuss basic sensory concepts, such as thresholds and adaption. organs—the eyes, ears, nose, tongue, and skin—receive signals from • Appreciate how expectations, contexts, emotions, and motivation the environment (sensation) and transfer those signals to the brain, infl uence perceptions. which processes the signals so we can understand them (percep- • Evaluate claims of ESP and the conclusions drawn from research tion). In this unit, we look first at the processes of sensation, the ways on those claims. in which the sense organs receive signals from the environment. The • Explain how the eyes receive, process, and transform light signals. eyes receive light waves. The ears receive sound waves. The nose and • tongue receive chemical signals, and the skin receives signals related Diff erentiate among the theories that explain our sensation and to pressure, warmth, body position, and pain. Next, perception is ex- perception of color. amined. The brain processes and organizes these signals in interest- • Describe gestalt perceptual principles, including fi gure–ground ing ways. Most of the time, our perceptions reflect the reality of the and grouping principles. world around us. Sometimes, though, our own expectations and the • Diff erentiate among the binocular and monocular depth cues that brain’s desire to organize cause our perceptions to differ from reality help us perceive 3D and motion. and allow illusions to fool us. By studying how we sense and perceive • Understand how perceptual constancies help us create meaning the world, we can understand more about ourselves and the world from sensory signals. around us. • Describe research on restored vision, sensory restriction, and This unit will help students appreciate how sensation and percep- perceptual adaptation and how it contributes our understanding tion interact to influence our thoughts and behaviors. The integrated of perception. processes of sensation and perception are the most basic ways we in- • Explain how the ears process sound waves, contributing to our teract with the world. By studying this unit, students will be able to: perception of pitch and sound location. • Diff erentiate between sensation and perception, understanding • Describe how the senses of touch, pain, taste, smell, and body that these processes are interrelated. position and movement work. • Understand how much information can be processed at any given • Explain how the senses interact. point in time.

Alignment to AP® Course Description Topic 4: Sensation and Perception (6–8% of AP® Examination)

Module Topic Essential Questions

Module 16 Selective Attention • What are the implications of having the ability to attend selectively to stimuli?

Transduction • What are the implications of sensory information not getting transformed and delivered to the brain properly?

Thresholds • Why are thresholds important to our ability to interact with the world around us?

Sensory Adaptation • How does sensory adaptation help people live day-to-day?

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Module 17 Perceptual Set • What are some benefits and drawbacks of perceptual set?

Context Eﬀ ects • How influential is context on our sensation and perception?

Emotion and Motivation • What are the implications of emotions and motivation influencing sensation and perception?

Module 18 The Stimulus Input: Light Energy • How is light important to vision? • What are the most important aspects of light that make vision possible?

The Eye • What are the most important aspects of the eye that make vision possible?

Visual Information Processing • How do feature detectors and parallel processing affect our visual perception?

Color Vision • How do we see color?

Module 19 Visual Organization • Why do we organize visual information in particular ways? • How does this type of organization help us understand the world around us?

Visual Interpretation • How does losing or regaining vision affect perception? • How does perceptual adaptation help us day-to-day?

Module 20 The Stimulus Input: Sound Waves • How are sound waves important to hearing? • What are the most important aspects of sound waves that make hearing possible?

The Ear • What aspects of the ear make hearing possible?

Module 21 Touch • Is touch a sensory system that is taken for granted?

Pain • What is the importance of pain in our lives?

Taste • How does our sense of taste affect other aspects of our lives?

Smell • What is the importance of smell in daily life?

Body Position and Movement • How can knowing about our body position and movement be important?

Sensory Interaction • Why is sensory interaction important?

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STUDENT ACTIVITIES: STUDENT ACTIVITIES • Fact or Falsehood? • Fact or Falsehood? • The Stroop Eﬀ ect Online • Binocular Vision vs. Monocular Vision • Understanding Weber’s Law • Autostereograms • FLIP IT VIDEOS Perceived Lunar Size • • Top-Down and Bottom-Up Processing The Ganzfeld • • Signal Detection Theory Displacement Goggles FLIP IT VIDEOS Module 17 • Gestalt Psychology • Monocular Cues TEACHER DEMONSTRATIONS • Testing for ESP Module 20 • ESP Trick—Precognition (Playing Card Trick) • ESP Trick—Precognition (Newspaper Article Trick) STUDENT ACTIVITY • ESP Trick—Clairvoyance • Fact or Falsehood? • ESP Trick—Mental Telepathy (Gray Elephant in Denmark Trick) FLIP IT VIDEO • ESP Trick—Mental Telepathy (Telephone Book Trick) • Theories of Hearing STUDENT ACTIVITIES • Fact or Falsehood? Module 21 • Belief in ESP Scale TEACHER DEMONSTRATIONS • Vision and Taste Module 18 STUDENT ACTIVITIES TEACHER DEMONSTRATION • Fact or Falsehood? • Movement Aftereﬀ ects • Warm Plus Cold Equals Hot STUDENT ACTIVITIES: • Tasting Salt and Sugar • Fact or Falsehood? FLIP IT VIDEO • Locating the Retinal Blood Vessels • Theories of Pain • Subjective Colors • The Color Vision Screening Inventory and Color Blindness FLIP IT VIDEOS • Rods and Cones in the Retina • Feature Detectors

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Modules 16 Basic Principles of Sensation and Perception 17 Inﬂ uences on Perception 18 Vision 19 Visual Organization and Interpretation 20 Hearing 21 The Other Senses

“ have perfect vision,” explains my colleague, Heather Sellers, an acclaimed writer Iand teacher. Her vision may be ﬁ ne, but there is a problem with her perception. She cannot recognize faces. In her memoir, You Don’t Look Like Anyone I Know, Sellers (2010) tells of awkward moments resulting from her lifelong prosopagnosia—face blindness.

In college, on a date at the Spaghetti Station, I returned from the bathroom and plunked myself down in the wrong booth, facing the wrong man. I remained unaware he was not my date even as my date (a stranger to me) accosted Wrong Booth Guy, and then stormed out of the Station. I can’t distinguish actors in movies and on television. I do not recognize myself in photos or videos. I can’t recognize my step- sons in the soccer pick-up line; I failed to determine which husband was mine at a party, in the mall, at the market.

Her inability to recognize faces means that people sometimes perceive her as snobby or aloof. “Why did you walk past me?” a neighbor might later ask. Similar to those of us with hearing loss who fake hearing during trite social conversation, Sellers sometimes fakes recognition. She often smiles at people she passes, in case she knows them. Or she pretends to know the person with whom she is talking. (To avoid the stress associated with such perception failures, people with serious hearing loss or with prosopagnosia often shy away from busy social situations.) But 150 Pacing Guide

Module Topic Standard Schedule Days Block Schedule Days MyersAP_SE_2e_Mod16_B.indd 150 1/21/14 9:32 AM Module 16 Selective Attention Transduction Thresholds Sensory Adaptation 11 Module 17 Perceptual Set Context Eﬀ ects Emotion and Motivation Module 18 The Stimulus Input: Light Energy The Eye 1 Visual Information Processing Color Vision 1.5 Module 19 Visual Organization 1 Visual Interpretation Module 20 The Stimulus Input: Sound Waves The Ear 1 Module 21 Touch Pain Taste Smell 11 Body Position and Movement Sensory Interaction

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there is an upside: When encountering someone who previously irritated her, she TEACH typically won’t feel ill will, because she doesn’t recognize the person. Unlike Sellers, most of us have (as Module 18 explains) a functioning area on the TRMTRM Discussion Starter underside of our brain’s right hemisphere that helps us recognize a familiar human Use the Module 16 Fact or Falsehood? face as soon as we detect it—in only one-seventh of a second (Jacques & Rossion, student activity from the TRM to intro- 2006). This ability illustrates a broader principle. Nature’s sensory gifts enable each duce the concepts from this module. animal to obtain essential information. Some examples: • Frogs, which feed on fl ying insects, have cells in their eyes that fi re only in TEACH response to small, dark, moving objects. A frog could starve to death knee - Teaching Tip deep in motionless fl ies. But let one zoom by and the frog’s “bug detector” cells snap awake. This unit provides numerous oppor- • Male silkworm moths’ odor receptors can detect one-billionth of an ounce tunities for active learning. Don’t be of sex attractant per second released by a female one mile away. That is why afraid to use your time to do the activi- silkworms continue to be. ties suggested in the text and from • Human ears are most sensitive to sound frequencies that include human the accompanying Teacher’s Resource voices, especially a baby’s cry. Materials. Students will understand the information better if they are able to In this unit, we’ll look more closely at what psychologists have learned about experience the material fi rsthand. how we sense and perceive the world around us. ENGAGE Online Activities Module 16 Use any or all of the following sites to help prepare for this unit or to give to Basic Principles of Sensation students to explore: Hugh Foley’s Sensation and and Perception Perception page at www.skidmore.

Beau Lark/Corbis Beau edu/~hfoley/perception.htm. Module Learning Objectives Psychology Tutorials at http://psych. hanover.edu/Krantz/tutor.html. 16-116-1 Contrast sensation and perception, and explain the difference between bottom-up and top-down processing. The Internet Psychology Lab (IPL) at www.ipsych.com. 16-2 Discuss how much information we can consciously attend to at once. Interactive Eye at www.nei.nih.gov/ 16-3 Identify the three steps that are basic to all our sensory systems. health/eyediagram.

16-416-4 Distinguish between absolute and difference thresholds, and discuss whether we can sense and be affected by stimuli below the absolute threshold.

16-516-5 Explain the function of sensory adaptation.

MyersAP_SE_2e_Mod16_B.indd 151ENGAGE 1/21/14 9:32 AM Online Activities The Online Psychology Laboratory (OPL) is an excellent website that has online experiments in all areas of psychology, especially sensation and perception, that students can participate in and download results to analyze. Using a computer lab, students can participate in several diﬀ erent experiments or ones that you choose by accessing http://opl.apa.org.

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sensation the process by which 16-116-1 What are sensation and perception? What do we mean by bottom-up TEACH our sensory receptors and nervous processing and top-down processing? system receive and represent Flip It stimulus energies from our Sellers’ curious mix of “perfect vision” and face blindness illustrates the distinction between environment. Help your students understand top- sensation and perception. When she looks at a friend, her sensation is normal: Her senses perception the process of detect the same information yours would, and they transmit that information to her brain. down and bottom-up processing organizing and interpreting And her perception—the processes by which her brain organizes and interprets sensory better by assigning the Flip It Video: sensory information, enabling us to input—is almost normal. Thus, she may recognize people from their hair, gait, voice, or par- recognize meaningful objects and ticular physique, just not their face. Her experience is much like the struggle you or I would events. Top-Down and Bottom-Up Processing. have trying to recognize a specifi c penguin in a group of waddling penguins. bottom - up processing analysis In our everyday experiences, sensation and perception blend into one continuous pro- that begins with the sensory cess. In this module, we slow down that process to study its parts, but in real life, our sensory TEACH receptors and works up to the brain’s integration of sensory and perceptual processes work together to help us decipher the world around us. Concept Connections information. • Our bottom-up processing starts at the sensory receptors and works up to higher Students may more readily identify top - down processing levels of processing. information processing guided by • Our top-down processing constructs perceptions from the sensory input by top-down processing with stereotyp- higher - level mental processes, as when we construct perceptions drawing on our experience and expectations. ing because both use previous expec- drawing on our experience and As our brain absorbs the information in FIGURE 16.1, bottom- up processing enables expectations. tations to make judgments about the our sensory systems to detect the lines, angles, and colors that form the fl ower and leaves. world around us. Help students under- selective attention the focusing Using top - down processing we interpret what our senses detect. of conscious awareness on a But how do we do it? How do we create meaning from the blizzard of sensory stimuli particular stimulus. stand that although stereotyping can bombarding our bodies 24 hours a day? Meanwhile, in a silent, cushioned, inner world, our be negative, it can also be very effi cient brain fl oats in utter darkness. By itself, it sees nothing. It hears nothing. It feels nothing. So, for people as they interact with certain how does the world out there get in? To phrase the question scientifi cally: How do we construct our representations of the external world? How do a campfi re’s fl icker, crackle, and smoky stimuli. Without top-down processing, scent activate neural connections? And how, from this living neurochemistry, do we cre- we would have to interpret the world ate our conscious experience of the fi re’s motion and temperature, its aroma and beauty? In search of answers to such questions, let’s look at some processes that cut across all our as if it were constantly new. It would sensory systems. To begin, where is the border between our conscious and unconscious be like having to relearn how to add in awareness, and what stimuli cross that threshold? math class every single day! Figure 16.1 What’s going on here? Our sensory and perceptual processes Selective Attention TEACH work together to help us sort out the complex images, including the 16-216-2 How much information do we consciously attend to at once? hidden couple in Sandro Del-Prete’s Common Pitfalls drawing, The Flowering of Love. Through selective attention, your awareness focuses, like a fl ashlight beam, on a minute Students may get bottom-up and aspect of all that you experience. By one estimate, your fi ve senses take in 11,000,000 bits top-down processing confused. of information per second, of which you consciously process about 40 (Wilson, 2002). Yet

Sandro Del-Prete your mind’s unconscious track intuitively makes great use of the other 10,999,960 bits. Until Help students remember the diﬀ er- reading this sentence, for example, you have been unaware that your shoes are pressing ence between the 2 concepts with against your feet or that your nose is in your line of vision. Now, suddenly, your attentional these tips: spotlight shifts. Your feet feel encased, your nose stubbornly intrudes on the words before you. While focusing on these words, you’ve also been blocking other parts of your environ- Bottom-up processing—we process ment from awareness, though your peripheral vision would let you see them easily. You can this way when we have no prior change that. As you stare at the X below, notice what surrounds these sentences (the edges of the page, the desktop, the ﬂ oor). knowledge. We start at the bottom X and work our way up. A classic example of selective attention is the cocktail party effect—your ability to attend Top-down processing—we process to only one voice among many (while also being able to detect your own name in an unat- tended voice). This effect might have prevented an embarrassing and dangerous situation in this way when we have prior knowledge. We start at the top and work to process details.

ENGAGEMyersAP_SE_2e_Mod16_B.indd 152 1/21/14 9:32 AM MyersAP_SE_2e_Mod16_B.indd 153 1/22/14 8:01 AM Online Activities Use this series of photos from the Tai-Wiki- Widbee blog to see if students notice glaring incongruities from a Colgate® dental ﬂ oss ad campaign: http://tywkiwdbi.blogspot. com/2013/01/what-do-you-notice-about- these-photos.html.

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2009, when two commercial airline pilots “lost track of time.” Focused on their laptops and conversation, they ignored alarmed air traffi c controllers’ attempts to reach them as they “Has a generation of texters, ENGAGE surfers, and twitterers evolved the overfl ew their Minneapolis destination by 150 miles. If only the controllers had known and enviable ability to process multiple spoken the pilots’ names. streams of novel information Enrichment in parallel? Most cognitive People with ADHD (attention-defi cit/ Selective Attention and Accidents psychologists doubt it.” -STEVEN PINKER, “NOT AT ALL,” 2010 hyperactivity disorder) seem to lack Text or talk on the phone while driving, or attend to a music player or GPS, and your selective attention will shift back and forth between the road and its electronic competition. But the ability to be selectively attentive. when a demanding situation requires it, you’ll probably give the road your full attention. Instead of fi ltering out unimportant You’ll probably also blink less. When focused on a task, such as reading, people blink less stimuli in order to focus on important than when their mind is wandering (Smilek et al., 2010). If you want to know whether your dinner companion is focused on what you’re saying, watch for eyeblinks and hope there ones, they attend to all stimuli in the won’t be too many. AP® Exam Tip environment, making it diffi cult, if not We pay a toll for switching attentional gears, especially when we shift to complex tasks, like noticing and avoiding cars around us. The toll is a slight and sometimes fatal delay in coping You may wish to think about impossible, to process information how the information on selective (Rubenstein et al., 2001). About 28 percent of traffi c accidents occur when people are chatting attention relates to something a correctly. on cell phones or texting (National Safety Council, 2010). One study tracked long-haul truck little less dangerous: studying. drivers for 18 months. The video cameras mounted in their cabs showed they were at 23 times The same principles apply. The greater risk of a collision while texting (VTTI, 2009). Mindful of such fi ndings, the United States more time you spend texting, TEACH tweeting, and Facebooking, the in 2010 banned truckers and bus drivers from texting while driving (Halsey, 2010). less focused you’ll be on the It’s not just truck drivers who are at risk. One in four teen drivers with cell phones material you’re trying to master. TRMTRM Teaching Tip admit to texting while driving (Pew, 2009). Multitasking comes at a cost: fMRI scans offer a A better strategy is to spend 25 minutes doing schoolwork and Apply selective attention to students’ biological account of how multitasking distracts from brain resources allocated to driving. schoolwork alone. Then you They show that brain activity in areas vital to driving decreases an average 37 percent when can reward yourself with a few lives by having them share experiences a driver is attending to conversation (Just et al., 2008). minutes of social networking. where they were either so caught up in Even hands-free cell-phone talking is more distracting than a conversation with pas- an activity that they missed something sengers, who can see the driving demands and pause the conversation. When University of Sydney researchers analyzed phone re- obvious in the environment, or when cords for the moments before a car crash, the environment was so distract- they found that cell-phone users (even with hands-free sets) were four times more at risk ing that they couldn’t concentrate. (McEvoy et al., 2005, 2007). Having a passen- Students with attention diffi culties ger increased risk only 1.6 times. This risk dif- may be reassured to know that others ference also appeared in an experiment that asked drivers to pull off at a freeway rest stop are frequently unable to concentrate 8 miles ahead. Of drivers conversing with a or that they, too, have times when passenger, 88 percent did so. Of those talk- their own intense concentration makes ing on a cell phone, 50 percent drove on by © The New Yorker Collection, 2009, Robert Leighton from cartoonbank.com. All Rights Reserved. (Strayer & Drews, 2007). “I wasn’t texting. I was building this ship in a bottle.” them miss things. Use Student Activity: The Stroop Eff ect Online from the TRM to show the diffi culty with attending to SALLY FORTH multiple stimuli at once.

Driven to distraction In driving-simulation experiments, people whose attention is diverted by cell- phone conversation make more driving errors. Sally Forth

MyersAP_SE_2e_Mod16_B.indd 152 1/21/14 9:32 AM MyersAP_SE_2e_Mod16_B.inddENGAGE 153 ENGAGE 1/22/14 8:01 AM Enrichment Active Learning When people get so caught up in an experi- Have students conduct research about laws ence that they miss out on obvious stimuli in governing cell phone use and texting while the environment, they are said to be having a driving. Have students see whether research fl o w experience. Flow, a term coined by Mihalyi into attention was used to craft or justify the Csikszentmihalyi (chik-sent-me-high), involves laws. Consider having your students develop being skilled at a challenging task that takes a public relations campaign about distracted away our sense of self-consciousness and driving that will use psychological principles to awareness of time and the presence of others appeal to their peers. Students can also try the around us. New York Times distracted driving simulation at www.nytimes.com/interactive/2009/07/19/ technology/20090719-driving-game. html?_r=0.

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TEACH Most European countries and American states now ban hand-held cell phones while driving (Rosenthal, 2009). Engineers are also devising ways to monitor drivers’ gaze and to Teaching Tip direct their attention back to the road (Lee, 2009). Have students speculate how selective Selective Inattention attention is related to the evolutionary At the level of conscious awareness, we are “blind” to all but a tiny sliver of visual stimuli. perspective. They can give examples of Researchers demonstrated this inattentional blindness dramatically by showing people a 1- minute video in which images of three black-shirted men tossing a basketball were each of the following: superimposed over the images of three white-shirted players (Neisser, 1979; Becklen & Cervone, 1983). The viewers’ supposed task was to press a key every time a black-shirted If we had to attend to every player passed the ball. Most focused their attention so completely on the game that they stimulus in the environment, we failed to notice a young woman carrying an umbrella saunter across the screen midway might be hindered from action. through the video (FIGURE 16.2). Seeing a replay of the video, viewers were astonished to see her (Mack & Rock, 2000). This inattentional blindness is a by-product of what we are However, if we miss important really good at: focusing attention on some part of our environment. stimuli in the environment due In a repeat of the experiment, smart- aleck researchers Daniel Simons and Christopher Chabris (1999) sent a gorilla - suited assistant through the swirl of players. During its 5- to to attention that is too selective, 9-second cameo appearance, the gorilla paused to thump its chest. Still, half the conscientious we may fall victim to all sorts of pass- counting viewers failed to see it. In another follow-up experiment, only 1 in 4 students engrossed in a cell-phone conversation while crossing a campus square noticed a clown-suited trouble—falls, car accidents, etc. unicyclist in their midst (Hyman et al., 2010). (Most of those not on the phone did notice.) At- tention is powerfully selective. Your conscious mind is in one place at a time. ENGAGE Given that most people miss someone in a gorilla or clown suit while their attention is riveted elsewhere, imagine the fun that magicians can have by manipulating our selective Online Activities attention. Misdirect people’s attention and they will miss the hand slipping into the pocket. inattentional blindness failing “Every time you perform a magic trick, you’re engaging in experimental psychology,” says Students may be interested in learning to see visible objects when our Teller, a magician and master of mind-messing methods (2009). attention is directed elsewhere. more about change blindness by visit- Magicians also exploit a form of inattentional blindness called change blindness. By change blindness failing to selectively riveting our attention on their left hand’s dramatic act, we fail to notice changes ing the website created by University of notice changes in the environment. made with their other hand. In laboratory experiments, viewers didn’t notice that, after a brief Illinois professor Daniel J. Simons, author visual interruption, a big Coke bottle had disappeared, a railing had risen, or clothing color had changed (Chabris & Simons, 2010; Resnick et al., 1997). Focused on giving directions to of the book, The Invisible Gorilla. He and a construction worker, two out of three people also failed to notice when he was replaced by his team research attention issues, and another worker during a staged interruption (FIGURE 16.3). Out of sight, out of mind. they have created several famous videos that demonstrate our blindness to change. Visit www.simonslab.com.

Figure 16.2 Testing selective attention In this classic experiment, viewers who were attending to basketball tosses among the black-shirted players usually failed to notice the umbrella- toting woman sauntering across the screen. (From Neisser, 1979.)

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Figure 16.3 TEACH Change blindness While a man (white hair) provides Concept Connections directions to a construction worker, two experimenters rudely Relate choice blindness to implicit pass between them. During this interruption, the original worker associations. Harvard researchers have switches places with another person wearing different-colored been examining how our unconscious clothing. Most people, focused on their direction giving, do not associations aﬀ ect prejudice and dis- notice the switch. crimination. Have students take the implicit association test online: An equally astonishing form of inattention is choice blindness. At one Swedish supermarket, people tasted two jams, indicated their preference, and then tasted again their pre- https://implicit.harvard.edu/implicit. ferred jam and explained their preference. Fooled by trick jars (see FIGURE 16.4) most people didn’t notice that they were actually “retasting” their nonpreferred jam. ENGAGE Online Activities Several versions of the change and choice blindness experiments are available on social media sites such as YouTube. You can ﬁ nd videos by Petter Johansson, and colleagues (2010).

Image is from the research paper by Lars Hall, searching for “change blindness Figure 16.4 experiment” or “choice blindness Marketplace magic Prankster Some stimuli, however, are so powerful, so strikingly distinct, that we experience pop - researchers Lars Hall, Petter experiment.” These videos may be out, as when we notice an angry face in a crowd. We don’t choose to attend to these stimuli; Johansson, and colleagues (2010) used as a classroom demonstration they draw our eye and demand our attention. invited people to sample two jams and pick one to retaste. By flipping the of these phenomena or as videos for Our selective attention extends even into our sleep, as we will see. jars after putting the lids back on, the researchers actually induced people students to watch on their own, which to “resample” their nonchosen jam. Transduction Yet, even when asked whether they you can then use as a starting oﬀ point noticed anything odd, most tasters were choice blind. Even when given for classroom discussion. 16-316-3 What three steps are basic to all our sensory systems? markedly different jams, they usually failed to notice the switch. Every second of every day, our sensory systems perform an amazing feat: They convert one form of energy into another. Vision processes light energy. Hearing processes sound waves. All our senses • receive sensory stimulation, often using specialized receptor cells. • transform that stimulation into neural impulses. transduction conversion of one • deliver the neural information to our brain. form of energy into another. In sensation, the transforming of The process of converting one form of energy into another that your brain can use is stimulus energies, such as sights, called transduction. Later in this unit, we’ll focus on individual sensory systems. How do sounds, and smells, into neural we see? Hear? Feel pain? Taste? Smell? Keep our balance? In each case, we’ll consider these impulses our brain can interpret. three steps—receiving, transforming, and delivering the information to the brain. We’ll also psychophysics the study see what psychophysics has discovered about the physical energy we can detect and its of relationships between the physical characteristics of stimuli, effects on our psychological experiences. such as their intensity, and our First, though, let’s explore some strengths and weaknesses in our ability to detect and psychological experience of them. interpret stimuli in the vast sea of energy around us.

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ENGAGE Thresholds 16-4 What are the absolute and difference thresholds, and do stimuli Enrichment below the absolute threshold have any infl uence on us? As long ago as 1888, Joseph Jastrow At this moment, you and I are being struck by X - rays and radio waves, ultraviolet and infra- speculated that lapses of attention, red light, and sound waves of very high and very low frequencies. To all of these we are blind and deaf. Other animals with differing needs detect a world that lies beyond our experience. slight fatigue, and other psychological Migrating birds stay on course aided by an internal magnetic compass. Bats and dolphins absolute threshold the locate prey using sonar, bouncing echoing sound off objects. Bees navigate on cloudy days changes could cause fl uctuations in minimum stimulation needed to by detecting invisible (to us) polarized light. the absolute threshold. detect a particular stimulus 50 percent of the time. The shades on our own senses are open just a crack, allowing us a restricted awareness signal detection theory a theory of this vast sea of energy. But for our needs, this is enough. ENGAGE predicting how and when we detect the presence of a faint stimulus Absolute Thresholds Enrichment (signal) amid background stimulation To some kinds of stimuli we are exquisitely sensitive. Standing atop a mountain on an ut- (noise). Assumes that there is no terly dark, clear night, most of us could see a candle fl ame atop another mountain 30 miles Gustav Fechner (1801–1887) devel- single absolute threshold and that detection depends partly on a away. We could feel the wing of a bee falling on our cheek. We could smell a single drop of oped 3 methods of experimental person’s experience, expectations, perfume in a three - room apartment (Galanter, 1962). measurement used to study sensory motivation, and alertness. German scientist and philosopher Gustav Fechner (1801–1887) studied our awareness of these faint stimuli and called them our absolute thresholds—the minimum stimula- phenomenon: tion necessary to detect a particular light, sound, pressure, taste, or odor 50 percent of the Method of limits. Begin with a time. To test your absolute threshold for sounds, a hearing specialist would expose each of Try This your ears to varying sound levels. For each tone, the test would defi ne where half the time minimal stimulus and increase it Try out this old riddle on a couple of you could detect the sound and half the time you could not. That 50-50 point would defi ne until the participant can perceive friends. “You’re driving a bus with your absolute threshold. 12 passengers. At your fi rst stop, 6 Detecting a weak stimulus, or signal, depends not only on the signal’s strength (such as it. This method helps determine passengers get off. At the second stop, 3 get off. At the third stop, 2 a hearing-test tone) but also on our psychological state—our experience, expectations, mo- the “just noticeable difference.” more get off but 3 new people get tivation, and alertness. Signal detection theory predicts when we will detect weak signals on. What color are the bus driver’s (measured as our ratio of “hits” to “false alarms”) (FIGURE 16.5). Signal detection theorists Method of right and wrong eyes?” Do your friends detect the signal—who is the bus driver?— seek to understand why people respond differently to the same stimuli (have you ever noticed cases. Present identical stimuli amid the accompanying noise? that some teachers are much more likely than others to detect students texting during class?) repeatedly—either single and why the same person’s reactions vary as circumstances change. Exhausted parents will notice the faintest whimper from a newborn’s cradle while failing to notice louder, unimport- stimuli at the threshold or pairs ant sounds. Lonely, anxious people at speed-dating events also respond with a low threshold of stimuli that are very similar. and thus tend to be unselective in reaching out to potential dates (McClure et al., 2010). The participant responds yes if perceived or if a difference exists, or no if not perceived or different.

Method of adjustment. Adjust © Inspirestock/Corbis a comparison stimulus until it appears identical to the standard stimulus. Every error is recorded and after many trials, the average Figure 16.5 Signal detection What three factors will error is computed. It, too, provides make it more likely that you correctly detect a

text message? a measure of just noticeable alert. are You (3) respond. and message text

difference. the see you that important is It (2) message. ANSWER: (1) You are expecting a text text a expecting are You (1) ANSWER:

TEACH Flip It Students can get additional help understanding signal detection theory ENGAGEMyersAP_SE_2e_Mod16_B.indd 156 1/21/14 9:32 AM MyersAP_SE_2e_Mod16_B.indd 157 1/23/14 1:57 PM by watching the Flip It Video: Signal Detection Theory on this topic. Active Learning Have students place an alarm clock (or forward to reach threshold. At other times the TEACH wristwatch) on a table in a quiet room. They sound will get louder and they will be able to Common Pitfalls should move away so that they can no longer step back. This changing sensitivity indicates hear the ticking, then gradually move toward that the “absolute threshold” is anything Students may wonder why anyone the clock until they begin to hear the sound. but absolute. cares about signal detection theory. This is the “momentary” threshold. If they The research in this area is especially Coren, S., Ward, L. M., & Enns, J. T. (1999). Sensation remain in place, occasionally they won’t be important to ﬁ elds where attention to and perception (5th ed.). Fort Worth, TX: Harcourt able to hear the sound and will need to step Brace. detail amid environmental distractions is paramount, such as air traﬃ c controllers, security screeners, law enforce- ment, and even ordinary car drivers.

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Percentage 100 Figure 16.6 ENGAGE of correct detections Absolute threshold Can I detect this sound? An absolute Active Learning threshold is the intensity at which 75

AJ Photo/Science Source a person can detect a stimulus With federal takeover of airport screen- half the time. Hearing tests locate these thresholds for various ing as a result of the 9/11 attacks, 50 frequency levels. Stimuli below your absolute threshold are accurate signal detection (like looking subliminal. for suspicious bags, packages, or activi- 25 Subliminal ties by passengers) by Transportation stimuli Safety Administration (TSA) employees

0 remains an important concern. Contact Low Absolute Medium threshold a nearby TSA offi ce or air traffi c control Intensity of stimulus offi ce to ask if representatives from your class might interview a supervi- Stimuli you cannot detect 50 percent of the time are subliminal—below your absolute sor about the following issues in signal threshold (FIGURE 16.6). Under certain conditions, you can be affected by stimuli so weak subliminal below one’s absolute threshold for conscious awareness. that you don’t consciously notice them. An unnoticed image or word can reach your visual detection: cortex and briefl y prime your response to a later question. In a typical experiment, the im- priming the activation, often unconsciously, of certain What policies are in place that age or word is quickly fl ashed, then replaced by a masking stimulus that interrupts the brain’s associations, thus predisposing processing before conscious perception (Van den Bussche et al., 2009). For example, one ex- one’s perception, memory, or increase accurate signal detection? periment subliminally fl ashed either emotionally positive scenes (kittens, a romantic couple) response. What training programs do you use or negative scenes (a werewolf, a dead body) an instant before participants viewed slides of people (Krosnick et al., 1992). The participants consciously perceived either scene as only a to equip screeners to make accurate fl ash of light. Yet the people somehow looked nicer if their image immediately followed un- “The heart has its reasons which calls about stimuli? perceived kittens rather than an unperceived werewolf. As other experiments confi rm, we can reason does not know.” -PASCAL, evaluate a stimulus even when we are not aware of it—and even when we are unaware of our PENSÉES, 1670 Do you offer incentives based on evaluation (Ferguson & Zayas, 2009). accurate performance? Why or How do we feel or respond to what we do not know and cannot describe? An imper- why not? ceptibly brief stimulus often triggers a weak response that can be detected by brain scanning (Blankenburg et al., 2003; Haynes & Rees, 2005, 2006). Only when the stimulus triggers Does your office engage in periodic synchronized activity in several brain areas does it reach consciousness (Dehaene, 2009). checks of accurate signal detection? Once again we see the dual-track mind at work: Much of our information processing occurs automatically, out of sight, off the radar screen of our conscious mind. What methods do you use to study So can we be controlled by subliminal messages? For more on that ques- this area? tion, see Thinking Critically About: Can Subliminal Messages Control Our Behavior? on the next page. Difference Thresholds To function effectively, we need absolute thresholds low enough to allow us to detect important sights, sounds, textures, tastes, and smells. We also need to detect small differences among stimuli. A musician must detect minute discrepancies when tuning an instrument. Students in the hallway must detect the sound of their friends’ voices amid all the other voices. Even after living two years in Scotland, sheep baa’s all sound alike to my ears. But not to those of ewes, which I have observed streaking, after shearing, directly to the baa of their lamb amid the chorus of

other distressed lambs. Eric Isselée/Shutterstock

MyersAP_SE_2e_Mod16_B.indd 156 1/21/14 9:32 AM MyersAP_SE_2e_Mod16_B.inddENGAGE 157 1/23/14 1:57 PM Enrichment Anthony Pratkanis identiﬁ ed factors that Many of the popular articles fail to report Pratkanis, A. (1990, August). Subliminal contribute to the public’s beliefs regarding scientific evidence that is critical of claims for sorcery then and now: Who is seducing subliminal inﬂ uence. subliminal persuasion. whom? Paper presented at the 98th annual Popular accounts of subliminal influence Belief in subliminal persuasion may serve convention of the American Psychological Association, Boston, MA. appeal to the “pop” psychology of the day. a need for many individuals. Subliminal Popular accounts link subliminal influence persuasion takes on a supernatural “the to the issue of the day. Subliminal influence devil made me do it” quality capable of first emerged as a national concern after explaining why Americans engage in the Korean War when brainwashing and irrational consumer behavior. hypnotic suggestion captured the nation’s imagination in films such as The Manchurian Candidate.

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Thinking Critically About TEACH Common Pitfalls Can Subliminal Messages Control Our Behavior? Some students may have heard that Hoping to penetrate our unconscious, entrepreneurs offer au- Subliminal dio and video programs to help us lose weight, stop smoking, persuasion? movie theatres in the 1950s used sub- Although subliminally or improve our memories. Soothing ocean sounds may mask presented stimuli can liminal advertising to increase sales of messages we cannot consciously hear: “I am thin”; “Smoke subtly infl uence people, tastes bad”; or “I do well on tests—I have total recall of infor- experiments discount popcorn and soda. They placed frames mation.” Such claims make two assumptions: (1) We can un- attempts at subliminal advertising and self- Babs Reingold for Worth Publishers Babs Reingold for Worth that said, “buy popcorn” and “buy consciously sense subliminal (literally, “below threshold”) stimuli. improvement. (The Coke” within movies, which was sup- (2) Without our awareness, these stimuli have extraordinary playful message here is suggestive powers. Can we? Do they? not actually subliminal— posed to encourage people to sublimi- because you can easily As we have seen, subliminal sensation is a fact. Remember perceive it.) nally want to purchase concessions. that an “absolute” threshold is merely the point at which we can This advertising ploy never happened. detect a stimulus half the time. At or slightly below this threshold, we will still detect the stimulus some of the time. The source of the myth, James Vicary, But does this mean that claims of subliminal persuasion actually lied about experiments he are also facts? The near- consensus among researchers is No. The laboratory research reveals a subtle, fl eeting effect. Priming conducted at a New Jersey movie the- thirsty people with the subliminal word thirst might therefore, for atre. His lie, however, led the Federal a moment, make a thirst- quenching beverage ad more persua- Communications Commission to ban sive (Strahan et al., 2002). Likewise, priming thirsty people with Lipton Iced Tea may increase their choosing the primed brand revealed no effects. Yet the students perceived themselves re- so-called “subliminal advertising” in (Karremans et al., 2006; Veltkamp et al., 2011; Verwijmeren ceiving the benefi ts they expected. Those who thought they 1974 (Source: www.snopes.com). et al., 2011a,b). But the subliminal-message hucksters claim had heard a memory recording believed their memories had something different: a powerful, enduring effect on behavior. improved. Those who thought they had heard a self - esteem To test whether subliminal recordings have this enduring ef- recording believed their self-esteem had grown. (Reading this TEACH fect, researchers randomly assigned university students to lis- research, one hears echoes of the testimonies that ooze from ten daily for 5 weeks to commercial subliminal messages claim- ads for such products. Some customers, having bought what Concept Connections ing to improve either self - esteem or memory (Greenwald et al., is not supposed to be heard [and having indeed not heard it!] Although subliminal advertising may 1991, 1992). But the researchers played a practical joke and offer testimonials like, “I really know that your recordings were switched half the labels. Some students who thought they were invaluable in reprogramming my mind.”) not work, priming does. If we are receiving affi rmations of self- esteem were actually hearing the Over a decade, Greenwald conducted 16 double - blind ex- exposed to stimuli about a specifi c memory-enhancement message. Others got the self - esteem periments evaluating subliminal self - help recordings. His results message but thought their memory was being recharged. were uniform: Not one of the recordings helped more than a subject, we are more likely to recog- Were the recordings effective? Students’ test scores for placebo (Greenwald, 1992). And placebos, you may remember, nize information about that subject in self- esteem and memory, taken before and after the 5 weeks, work only because we believe they will work. the environment. This phenomenon is related to context eff ects, which is discussed in more detail in Module 17. The difference threshold (or the just noticeable difference [jnd]) is the minimum difference a person can detect between any two stimuli half the time. ENGAGE That difference threshold increases with the size of TRMTRM the stimulus. Thus, if you add 1 ounce to a 10-ounce Active Learning The difference weight, you will detect the difference; add 1 ounce to a threshold In this 100-ounce weight and you probably will not. Weber’s law can be applied to many computer-generated copy of the Twenty-third Psalm, In the nineteenth century, Ernst Weber noted situations. Robert Cialdini suggests each line of the typeface something so simple and so widely applicable that we having students imagine a man who increases slightly. How still refer to it as Weber’s law. This law states that for many lines are required for wants to buy a 3-piece suit and a you to experience a just an average person to perceive a difference, two stimuli noticeable difference? must differ by a constant minimum percentage (not a sweater. If you were the salesperson, which should you show him fi rst in order to get him to spend the most money? You might think it best to sell the sweater fi rst. Having spent a lot on themMyersAP_SE_2e_Mod16_B.indd after, rather 158 than before, a more expen- ENGAGE 1/21/14 9:32 AM MyersAP_SE_2e_Mod16_B.indd 159 1/21/14 9:32 AM a suit, the customer might be reluctant sive purchase. Use Student Activity: Under- to spend more on a sweater. However, standing Weber’s law from the TRM to further Active Learning sales motivation analysts suggest the demonstrate this concept. To apply Weber’s law, students need 3 quarters, 2 envelopes, and a pair of shoes. Have them opposite. Sell the suit fi rst because the Cialdini, R. B. (1993). Infl uence: Science and practice additional cost of the sweater will not (3rd ed.). New York: HarperCollins. place one quarter in one envelope and the be so readily noticed. If the man has remaining 2 quarters in the other. Lifting each just paid $300 for a suit, an addi- envelope, they can easily determine which is tional $75 for a sweater will not seem heavier. Now have them put each envelope in excessive. The same applies to other a shoe. When they lift the shoes, one at a time, accessories, such as a shirt or shoes. the weight diff erence will be imperceptible. As a rule, people will almost always Coren, S., Ward, L. M., & Enns, J. T. (2003). Sensation pay more for accessories if they buy and perception (6th ed.). New York: Wiley.

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constant amount). The exact proportion varies, depending on the stimulus. Two lights, for example, must differ in intensity by 8 percent. Two objects must differ in weight by 2 per- difference threshold the ENGAGE cent. And two tones must differ in frequency by only 0.3 percent (Teghtsoonian, 1971). For minimum difference between two stimuli required for detection 50 Active Learning example, to be perceptibly different, a 50-ounce weight must differ from another by about percent of the time. We experience an ounce, a 100-ounce weight by about 2 ounces. the difference threshold as a just A fun way to demonstrate the impor- noticeable difference (or jnd). tance of sensory adaptation is to ask Sensory Adaptation Weber’s law the principle that, to be perceived as different, two students what a day would be like if stimuli must differ by a constant 16-516-5 What is the function of sensory adaptation? minimum percentage (rather than a they felt diff erent items they wore on constant amount). a daily basis like a wristwatch, glasses, Entering your neighbors’ living room, you smell a musty odor. You wonder how they can sensory adaptation diminished socks, etc. Be descriptive as you ask stand it, but within minutes you no longer notice it. Sensory adaptation has come to your sensitivity as a consequence of rescue. When we are constantly exposed to a stimulus that does not change, we become less constant stimulation. students about these items they are aware of it because our nerve cells fi re less frequently. (To experience sensory adaptation, wearing: Do you feel your socks grip- move your watch up your wrist an inch: You will feel it—but only for a few moments.) Why, then, if we stare at an object without fl inching, does it not vanish from sight? Be- ping your ankles? Your watch squeez- cause, unnoticed by us, our eyes are always moving. This continual fl itting from one spot to “We need above all to know about changes; no one wants or ing your wrist? Students become another ensures that stimulation on the eyes’ receptors continually changes (FIGURE 16.7). needs to be reminded 16 hours squirmy as they “feel” these items What if we actually could stop our eyes from moving? Would sights seem to vanish, a day that his shoes are on.” as odors do? To fi nd out, psychologists have devised ingenious instruments that maintain -NEUROSCIENTIST DAVID HUBEL (1979) rather intensely! a constant image on the eye’s inner surface. Imagine that we have fi tted a volunteer, Mary, with one of these instruments—a miniature projector mounted on a contact lens (FIGURE 16.8a on the next page). When Mary’s eye moves, the image from the projector moves as ENGAGE well. So everywhere that Mary looks, the scene is sure to go. If we project images through this instrument, what will Mary see? At fi rst, she will see Active Learning the complete image. But within a few seconds, as her sensory system begins to fatigue, Divide students into small groups and things get weird. Bit by bit, the image vanishes, only to reappear and then disappear—often have one person in the group com- in fragments (Figure 16.8b). Although sensory adaptation reduces our sensitivity, it offers an important benefi t: free- plete a simple task, such as completing dom to focus on informative changes in our environment without being distracted by back- a crossword puzzle or word fi nd. Have ground chatter. Stinky or heavily perfumed classmates don’t notice their odor because, like you and me, they adapt to what’s constant and detect only change. Our sensory receptors the other members of the group test diff erent types of noise interference on the person’s ability to complete the Figure 16.7 The jumpy eye Our gaze jumps task. They should record their results. from one spot to another every third of a second or so, as eye- Have them consider the following tracking equipment illustrated in this photograph of Edinburgh’s Princes questions: Street Gardens (Henderson, 2007). The circles represent fixations, and the Does noise with words (reading numbers indicate the time of fixation a story) interfere more than in milliseconds (300 milliseconds = three-tenths of a second). noise without words (static or yelling “blah, blah” )? Does music with words interfere more than music without words? How loud does the noise have to be for it to become distracting? John M. Henderson

MyersAP_SE_2e_Mod16_B.indd 158 1/21/14 9:32 AM MyersAP_SE_2e_Mod16_B.inddENGAGE 159 1/21/14 9:32 AM Active Learning Adaptation to the taste of one substance can and water until it becomes less bitter. The glass aﬀ ect the taste of another, either decreasing or of fresh water will taste sweet. The variability increasing our sensitivity to it. Using 3 glasses in the taste of ordinary tap water following of water (one mixed with salt, one mixed adaptation to various substances will surprise with vinegar, and one fresh), have a student many students. volunteer come to the front of the classroom. Fisher, J. (1979). Body magic. New York: Stein & Day. Have the student taste the saltwater and hold it in his or her mouth for a time; it will gradually taste less salty. If the student then takes a glass of fresh water, it will taste bitter or sour. Have another student volunteer come to the front of the room and hold a mouthful of vinegar

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CLOSE & ASSESS Figure 16.8 Sensory adaptation: Now you see it, now you don’t! Exit Assessment (a) A projector mounted on a contact lens makes the projected image Several concepts in this module may move with the eye. (b) Initially, the be diffi cult to understand and are person sees the stabilized image, but soon she sees fragments often confused. To assess whether fading and reappearing. (From “Stabilized images on the retina,” by students understand these concepts, R. M. Pritchard. Copyright © 1961 Scientific American, Inc. All rights ask them to give examples and provide reserved.) (a) (b) defi nitions or compare and contrast the following: are alert to novelty; bore them with repetition and they free our attention for more important things. We will see this principle again and again: We perceive the world not exactly as it Top-down vs. bottom-up is, but as it is useful for us to perceive it. processing Our sensitivity to changing stimulation helps explain television’s attention -grabbing power. Cuts, edits, zooms, pans, sudden noises—all demand attention. The phenomenon is irresist- Absolute vs. difference thresholds ible even to TV researchers. One noted that even during interesting conversations, “I cannot for the life of me stop from periodically glancing over to the screen” (Tannenbaum, 2002). Sensory adaptation even infl uences our perceptions of emotions. By creating a 50-50 morphed blend of an angry and a scared face, researchers showed that our visual system adapts to a static facial expression by becoming less responsive to it (Butler et al., 2008) (FIGURE 16.9). Sensory adaptation and sensory thresholds are important ingredients in our perceptions of the world around us. Much of what we perceive comes not just from what’s “out there” but also from what’s behind our eyes and between our ears.

Figure 16.9 Emotion adaptation Gaze at the angry face on the left for 20 to 30 seconds, then look at the center face (looks scared, yes?). Then gaze at the scared permission from Elsevier. face on the right for 20 to 30 seconds, before returning to the center face (now looks angry, yes?). Christopher J. Fox, Jason S. Barton. Factors contributing to the Reprinted from Brain Research, Vol 1191, Andrea Butler, Ipek Oruc, 1191, Andrea Butler, Reprinted from Brain Research, Vol adaptation after effects of facial expression, Pg 116–126, 2008, with

Before You Move On ᭤ ASK YOURSELF Can you recall a recent time when, your attention focused on one thing, you were oblivious to something else (perhaps to pain, to someone’s approach, or to background music)? ᭤ TEST YOURSELF Explain how Heather Sellers’ experience of prosopagnosia illustrates the difference between sensation and perception. Answers to the Test Yourself questions can be found in Appendix E at the end of the book.

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Module 16 Review

16-116-1 What are sensation and perception? What • Researchers in psychophysics study the relationships do we mean by bottom-up processing and between stimuli’s physical characteristics and our top-down processing? psychological experience of them.

Sensation is the process by which our sensory receptors • 16-416-4 What are the absolute and difference and nervous system receive and represent stimulus thresholds, and do stimuli below the absolute energies from our environment. Perception is the process threshold have any infl uence on us? of organizing and interpreting this information, enabling recognition of meaningful events. Sensation and • Our absolute threshold for any stimulus is the minimum perception are actually parts of one continuous process. stimulation necessary for us to be consciously aware of • Bottom-up processing is sensory analysis that begins at the it 50 percent of the time. Signal detection theory predicts entry level, with information fl owing from the sensory how and when we will detect a faint stimulus amid receptors to the brain. Top-down processing is information background noise. Individual absolute thresholds vary, processing guided by high-level mental processes, as depending on the strength of the signal and also on our when we construct perceptions by fi ltering information experience, expectations, motivation, and alertness. through our experience and expectations. • Our difference threshold (also called just noticeable difference, or jnd) is the difference we can discern between two 16-216-2 How much information do we consciously stimuli 50 percent of the time. Weber’s law states that attend to at once? two stimuli must differ by a constant percentage (not a constant amount) to be perceived as different. • We selectively attend to, and process, a very limited portion of incoming information, blocking out much and often shifting • Priming shows that we can process some information the spotlight of our attention from one thing to another. from stimuli below our absolute threshold for conscious awareness. But the effect is too fl eeting to enable people • Focused intently on one task, we often display inattentional to exploit us with subliminal messages. blindness (including change blindness) to other events and changes around us. 16-516-5 What is the function of sensory adaptation?

16-316-3 What three steps are basic to all our sensory systems? • Sensory adaptation (our diminished sensitivity to constant or routine odors, sights, sounds, and touches) focuses our • Our senses (1) receive sensory stimulation (often using attention on informative changes in our environment. specialized receptor cells); (2) transform that stimulation into neural impulses; and (3) deliver the neural information to the brain. Transduction is the process of converting one form of energy into another.

Multiple-Choice Questions Answers to Multiple-Choice

1. What occurs when experiences inﬂ uence our 2. What principle states that to be perceived as different, Questions interpretation of data? two stimuli must differ by a minimum percentage rather a. Selective attention than a constant amount? 1. d b. Transduction a. Absolute threshold 2. e c. Bottom-up processing b. Different threshold d. Top-down processing c. Signal detection theory e. Signal detection theory d. Priming e. Weber’s law

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3. a 5. e 3. What do we call the conversion of stimulus energies, like 5. Tyshane went swimming with friends who did not want sights and sounds, into neural impulses? to get into the pool because the water felt cold. Tyshane 4. c a. Transduction jumped in and after a few minutes declared, “It was cold b. Perception when I ﬁ rst got in, but now my body is used to it. Come c. Priming on in!” Tyshane’s body became accustomed to the water d. Signal detection theory due to e. Threshold a. perceptual set. b. absolute threshold. 4. Natalia is washing her hands and adjusts the faucet c. difference threshold. handle until the water feels just slightly hotter than it did d. selective attention. before. Natalia’s adjustment until she feels a difference is e. sensory adaptation. an example of a. a subliminal stimulus. b. an absolute threshold. c. a difference threshold. d. signal detection. e. Weber’s law.

Answer to Practice FRQ 2 Practice FRQs 1. 2. 1 point: Absolute threshold is the mini- Explain how bottom-up and top-down processes work Marisol is planning a ski trip for spring break. Defi ne together to help us decipher the world around us.. absolute threshold and difference threshold, and explain mum stimulation that can be detected how each one might play a role in her perception of the Answer 50% of the time. winter weather she will experience. 1 point: Bottom-up processing starts at the sensory (4 points) 1 point: Diff erence threshold is the receptors and works up to higher levels of processing. minimum change in stimulation a per- 1 point: Top-down processing constructs perceptions son can detect 50% of the time. from the sensory input by drawing on our experience and expectations. 1 point: Absolute threshold real-world examples can include, but are not limited to, the following: (1) the light- est wind Marisol can feel, or (2) the fi rst realization that it is snowing. 1 point: Diff erence threshold real- world examples can include, but are not limited to, the following: (1) being aware of a slight change in temperature, or (2) being aware of a slight change in atmospheric pressure as Marisol skis down the mountain.

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TEACH Module 17 TRMTRM Discussion Starter Use the Module 17 Fact or Falsehood? student activity from the TRM to intro- Inﬂ uences on Perception duce the concepts from this module.

TEACH

Module Learning Objectives Dolding/cultura/Corbis Nick © Teaching Tip 17-117-1 Explain how our expectations, contexts, emotions, and motivation infl uence our perceptions. Ask your class to shout out the answers to the following questions. “What do 17-217-2 List the claims of ESP, and discuss the conclusions of most these letters spell?” (Write folk on the research psychologists after putting these claims to the test. board.) “How about these?” (Write croak.) “And what do these letters spell?” (Write soak.) “What do we Perceptual Set call the white of an egg?” Students will respond “yolk” even though the 17-117-1 How do our expectations, contexts, emotions, and motivation infl uence our perceptions? answer is “egg white.” As everyone knows, to see is to believe. As we less fully appreciate, to believe is to see. This activity demonstrates the Through experience, we come to expect certain results. Those expectations may give us power of perceptual set. Students get a perceptual set, a set of mental tendencies and assumptions that greatly affects (top- perceptual set a mental into a pattern of spelling the word in down) what we perceive. Perceptual set can infl uence what we hear, taste, feel, and see. predisposition to perceive one Consider: Is the image in the center picture of FIGURE 17.1 a young woman’s profi le thing and not another. a particular way, so when one homo- or an old woman? What we see in such a drawing can be infl uenced by fi rst looking at phone word is introduced, they will either of the two unambiguous versions (Boring, 1930). Everyday examples of perceptual set abound. In 1972, a British newspaper published spell it consistently with the pattern. unretouched photographs of a “monster” in Scotland’s Loch Ness—“the most amazing TEACH Concept Connections Perceptual set is similar to priming. Figure 17.1 What we expect to see is often infl u- Perceptual set Show a friend either the left or enced by what is around us. right image. Then show the center image and ask, “What do you see?” Whether your friend reports seeing a young woman’s profile or an old woman may depend on which of the other two drawings was viewed first. In each of those images, the meaning is clear, and it will establish perceptual expectations.

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pictures ever taken,” stated the paper. If this information creates in you the same ex- ENGAGE pectations it did in most of the paper’s readers, you, too, will see the monster in a similar photo in FIGURE 17.2. But when a skeptical researcher approached the Active Learning photos with different expectations, he saw a curved tree limb—as had others Have students create their own percep- the day the photo was shot (Campbell, 1986). With this different perceptual set, you may now notice that the object is fl oating motionless, with ripples tual set studies by packaging generic outward in all directions—hardly what we would expect of a lively monster. foods and drinks in name-brand Once we have formed a wrong idea about reality, we have more diffi culty see- packaging. They can then do taste ing the truth. Perceptual set can also affect what we hear. Consider the kindly airline pilot tests with their friends or family to see who, on a takeoff run, looked over at his depressed co - pilot and said, “Cheer whether the packaging matters. How © The New Yorker Collection, 2002, Leo Cullum from cartoonbank.com. All Rights Reserved. up.” Expecting to hear the usual “Gear up,” the co-pilot promptly raised the wheels—before do the people judge the products: they left the ground (Reason & Mycielska, 1982). same, better, or worse? Have students discuss how perceptual set infl uences Figure 17.2 Believing is seeing What do you people’s perceptions of the products. perceive? Is this Nessie, the Loch Ness monster, or a log? Hulton Archive/Getty Images

Try This Perceptual set similarly affects taste. One experiment invited some bar patrons to When shown the phrase sample free beer (Lee et al., 2006). When researchers added a few drops of vinegar to a Mary had a brand-name beer, the tasters preferred it—unless they had been told they were drinking a little lamb vinegar-laced beer. Then they expected, and usually experienced, a worse taste. In another many people perceive what they expect, and miss the repeated experiment, preschool children, by a 6-to-1 margin, thought french fries tasted better when word. Did you? served in a McDonald’s bag rather than a plain white bag (Robinson et al., 2007). What determines our perceptual set? As Module 47 will explain, through experience we TEACH form concepts, or schemas, that organize and allow us to interpret unfamiliar information. Our pre-existing schemas for old women and young women, for monsters and tree limbs, Concept Connections all inﬂ uence how we interpret ambiguous sensations with top - down processing. Schemas are an important concept in “We hear and apprehend only In everyday life, stereotypes about gender (another instance of perceptual set) can color what we already half know.” perception. Without the obvious cues of pink or blue, people will struggle over whether to psychology. Swiss psychologist Jean -HENRY DAVID THOREAU, JOURNAL, call the new baby “he” or “she.” But told an infant is “David,” people (especially children) 1860 Piaget developed the idea of schemas may perceive “him” as bigger and stronger than if the same infant is called “Diana” (Stern to describe the ways in which we con- & Karraker, 1989). Some differences, it seems, exist merely in the eyes of their beholders. ceptualize the world. These schemas Context Effects help explain why we are vulnerable A given stimulus may trigger radically different perceptions, partly because of our differing to our perceptual sets. Schemas are perceptual set, but also because of the immediate context. Some examples: further discussed in Unit IX.

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Culture and context effects What is above the woman’s head? TEACH In a classic study from nearly a half-century ago, most East Africans Diversity Connections perceived the woman as balancing a metal box or can on her head The drawing at the top of p. 165 is an and the family as sitting under a tree. Westerners, for whom corners excellent example of how culture infl u- and boxlike architecture were more common, were more likely to ences perception. Most Westerners perceive the family as being indoors, with the woman sitting under a have no trouble interpreting the scene window. (Adapted from Gregory & Gombrich, 1973.) of people sitting inside a dwelling. They do not confuse the window with a box on the woman’s head. However, those from other cultures who do • Imagine hearing a noise interrupted by the words “eel is on the wagon.” Likely, you not share the same perceptual sets would actually perceive the fi rst word as wheel. Given “eel is on the orange,” you perceive the scene diff erently. Help would hear peel. This curious phenomenon, discovered by Richard Warren, suggests that the brain can work backward in time to allow a later stimulus to determine how students see the perspective of others we perceive an earlier one. The context with this picture. creates an expectation that, top - down, infl uences our perception (Grossberg, 1995). TEACH • Does the pursuing dog in FIGURE 17.3 look bigger than the one being pursued? If Teaching Tip so, you are experiencing a context effect. Use the fi gures throughout the unit • How tall is the shorter player in to demonstrate to students these per- FIGURE 17.4? ceptual concepts. Have students fi nd their own examples of these and create a library of visual illusions to use with students. You might direct them to the website http://dragon.uml.edu/psych/.

ENGAGE Enrichment Research on context shows that situations can have a powerful eﬀ ect on Dennis Geppert/Holland Sentinel behavior: Figure 17.4 Big and “little” The “little guy” Studying should not occur while shown here is actually a 6’9” former Hope College basketball center who lying in bed. Students who do Figure 17.3 would tower over most of us. But The interplay between context and he seemed like a short player when this often associate studying with emotional perception The context matched in a semi-pro game against the sleeping because they study where makes the pursuing dog look bigger than world’s tallest basketball player at that the pursued. It isn’t. time, 7'9'' Sun Ming Ming from China. they sleep. For effective studying, a designated place should be created where all the necessary supplies are available. Sleep researchers assisting those suffering from insomnia suggest MyersAP_SE_2e_Mod17_B.indd 164 1/21/14 9:33 AM MyersAP_SE_2e_Mod17_B.indd 165 1/21/14 9:33 AM ENGAGE designating the bed for sleeping Active Learning only and not for watching TV or reading. People may come to Have your teaching colleagues provide baby associate the bed with those other pictures of themselves or their children that activities rather than with sleeping, do not give away the baby’s gender. Have which can hinder their ability to fall students guess what gender the baby is and asleep easily. identify which cues they are using to determine the gender. You can discuss with students how we use our schemas and perceptual sets to make sense of ambiguous stimuli.

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TEACH Emotion and Motivation Perceptions are infl uenced, top-down, not only by our expectations and by the context, but Concept Connections also by our emotions and motivation. Link this discussion of emotion and Hearing sad rather than happy music can predispose people to perceive a sad meaning in spoken homophonic words—mourning rather than morning, die rather than dye, pain motivation to the discussion of the rather than pane (Halberstadt et al., 1995). same topics in Unit VIII. How we Researchers (Proffi tt, 2006a,b; Schnall et al., 2008) have demonstrated the power of perceive the world is infl uenced by our emotions with other clever experiments showing that current emotional state and whether • walking destinations look farther away to those who have been fatigued by prior exercise. we are motivated to notice details. • a hill looks steeper to those who are wearing a heavy backpack or have just been “When you’re hitting the ball, exposed to sad, heavy classical music rather than light, bouncy music. As with so many it comes at you looking like a ENGAGE grapefruit. When you’re not, of life’s challenges, a hill also seems less steep to those with a friend beside them. it looks like a blackeyed pea.” • a target seems farther away to those throwing a heavy rather than a light object at it. Active Learning -FORMER MAJOR LEAGUE BASEBALL PLAYER GEORGE SCOTT Even a softball appears bigger when you are hitting well, observed other researchers, after Have students pick an infl uence on asking players to choose a circle the size of the ball they had just hit well or poorly (Witt & perception mentioned in the text and Proffi tt, 2005). When angry, people more often perceive neutral objects as guns (Bauman & DeSteno, 2010). devise a test of that concept that they Motives also matter. Desired objects, such as a water bottle when thirsty, seem closer can conduct with their peers. You can (Balcetis & Dunning, 2010). This perceptual bias energizes our going for it. Our motives also direct our perception of ambiguous images. use these as classroom demonstra- Emotions color our social perceptions, too. Spouses who feel loved and appreciated tions or as a project students conduct perceive less threat in stressful marital events—“He’s just having a bad day” (Murray et al., with fellow students outside class with 2003). Professional referees, if told a soccer team has a history of aggressive behavior, will assign more penalty cards after watching videotaped fouls (Jones et al., 2002). permission from the administration. * * * Emotion and motivation clearly infl uence how we perceive sensations. But what to make of extrasensory perception, which claims that perception can occur apart from sensory input? For more on that question, see Thinking Critically About: ESP—Perception Without Sensation? Before You Move On ᭤ ASK YOURSELF Can you recall a time when your expectations have predisposed how you perceived a person (or group of people)? ᭤ TEST YOURSELF What type of evidence shows that, indeed, “there is more to perception than meets the senses”? Answers to the Test Yourself questions can be found in Appendix E at the end of the book.

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Thinking Critically About TEACH ESP—Perception Without Sensation? TRMTRM Diversity Connections

What are the claims of ESP, and what Most research psychologists and scientists—including Teaching skepticism for ESP should 17-217-2 have most research psychologists 96 percent of the scientists in the U.S. National Academy be tempered so as not to alienate stu- concluded after putting these claims to of Sciences—are skeptical that paranormal phenomena ex- the test? ist (McConnell, 1991). But reputable universities in many lo- dents with various religious beliefs and cations, including Great Britain, the Netherlands, and Australia, experiences, such as beliefs in angels, Without sensory input, are we capable of extrasensory per- have added faculty chairs or research units in parapsychology dreams as visions, etc. The goal of this ception (ESP)? Are there indeed people—any people—who (Turpin, 2005). These researchers perform scientifi c experiments can read minds, see through walls, or foretell the future? Nearly searching for possible ESP and other paranormal phenomena. skepticism should be to avoid scam half of Americans believe there are (AP, 2007; Moore, 2005). Before seeing how parapsychologists do research on ESP, let’s artists rather than to dispel particular The most testable and, for this unit, most relevant parapsy- consider some popular beliefs. chological concepts are belief systems. Use Student Activity: PREMONITIONS OR PRETENSIONS? • telepathy: mind - to - mind communication. Belief in ESP Scale from the TRM to Can psychics see into the future? Although one might wish for a • clairvoyance: perceiving remote events, such as a house assess your students’ opinions of the psychic stock forecaster, the tallied forecasts of “leading psychics” on fi re in another state. reveal meager accuracy. During the 1990s, the tabloid psychics existence of psychic or ESP abilities. • precognition: perceiving future events, such as an were all wrong in predicting surprising events. (Madonna did not unexpected death in the next month. become a gospel singer, the Statue of Liberty did not lose both Closely linked is psychokinesis, or “mind over matter,” such its arms in a terrorist blast, Queen Elizabeth did not abdicate her ENGAGE as levitating a table or infl uencing the roll of a die. (The claim throne to enter a convent.) And the new-century psychics have TRMTRM is illustrated by the wry request, “Will all those who believe in missed the big- news events. Where were the psychics on 9/10 Active Learning psychokinesis please raise my hand?”) when we needed them? Why, despite a $50 million reward offered, Have students collect horoscopes or If ESP is real, we would need to overturn the scientifi c un- could none of them help locate terrorist Osama bin Laden after other precognitive predictions from derstanding that we are creatures whose minds are tied to our the horror of 9/11, or step forward to predict the impending stock physical brains and whose perceptual experiences of the world crashes in 2008? In 30 years, unusual predictions have almost publications found in supermarket are built of sensations. Sometimes new evidence does overturn never come true, and psychics have virtually never anticipated any checkout aisles over a period of our scientifi c preconceptions. Science, as we will see through- of the year’s headline events (Emory, 2004, 2006). In 2010, when out this book, offers us various surprises—about the extent of a mine collapse trapped 33 miners, the Chilean government re- time. Have them record the predic- the unconscious mind, about the effects of emotions on health, portedly consulted four psychics. Their verdict? “They’re all dead” tions made about diff erent events about what heals and what doesn’t, and much more. (Kraul, 2010). But 69 days later, all 33 were rescued. or diff erent astrological signs and Moreover, the hundreds of psychic visions offered to police departments have been no more accurate than guesses made compare those predictions with what by others (Nickell, 1994, 2005; Radford, 2010; Reiser, 1982). actually occurred. They can do this by But their sheer volume does increase the odds of an occasional correct guess, which psychics can then report to the media. checking the newspapers for reports Police departments are wise to all this. When researchers asked related to the predictions or keep a the police departments of America’s 50 largest cities whether journal of what happens in their lives they ever had used psychics, 65 percent said No (Sweat & Durm, 1993). Of those that had, not one had found them help- to check if their daily horoscope is ful. Vague predictions can also later be interpreted (“retrofi tted”) correct. What they will likely fi nd is that predictions made by astrologers are extrasensory perception (ESP) the controversial claim usually ambiguous enough to apply that perception can occur apart from sensory input; includes telepathy, clairvoyance, and precognition. to multiple situations, which begs the parapsychology the study of paranormal phenomena, question: Can a prediction that applies including ESP and psychokinesis. to many outcomes really be considered Dan Piraro Dan (continued on next page) accurate if it came true? 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ENGAGE Thinking Critically About (continued)

TRMTRM Online Activities to match events that provide a perceptual set for “understand- This scientifi c attitude has led both believers and skep- ing” them. Nostradamus, a sixteenth - century French psychic, tics to agree that what parapsychology needs is a reproduc- The following websites off er informa- explained in an unguarded moment that his ambiguous prophe- ible phenomenon and a theory to explain it. Parapsychologist tion about scientifi c testing of psychic cies “could not possibly be understood till they were interpreted Rhea White (1998) spoke for many in saying that “the image phenomena: after the event and by it.” of parapsychology that comes to my mind, based on nearly Are the spontaneous “visions” of everyday people any more 44 years in the fi eld, is that of a small airplane [that] has been The James Randi Educational accurate? Do dreams, for example, foretell the future, as people perpetually taxiing down the runway of the Empirical Science Foundation homepage at from both Eastern and Western cultures tend to believe—mak- Airport since 1882 . . . its movement punctuated occasionally ing some people more reluctant to fl y after dreaming of a plane by lifting a few feet off the ground only to bump back down www.randi.org. crash (Morewedge & Norton, 2009)? Or do they only seem to on the tarmac once again. It has never taken off for any sus- The Rhine Research Center Web site do so when we recall or reconstruct them in light of what has tained fl ight.” already happened? Two Harvard psychologists tested the pro- How might we test ESP claims in a controlled, reproducible at www.rhine.org. phetic power of dreams after superhero aviator Charles Lind- experiment? An experiment differs from a staged demonstra- After searching these sites, have stu- bergh’s baby son was kidnapped and murdered in 1932, but tion. In the laboratory, the experimenter controls what the “psy- before the body was discovered (Murray & Wheeler, 1937). chic” sees and hears. On stage, the psychic controls what the dents address the following questions: When invited to report their dreams about the child, 1300 vi- audience sees and hears. Why are psychics generally sionaries submitted dream reports. How many accurately en- The search for a valid and reliable test of ESP has resulted visioned the child dead? Five percent. And how many also in thousands of experiments. After digesting data from 30 such unwilling to be scientifically tested? correctly anticipated the body’s location—buried among trees? studies, parapsychologist Lance Storm and his colleagues Do you think paranormal Only 4 of the 1300. Although this number was surely no better (2010a,b) concluded that, given participants with experience or than chance, to those 4 dreamers the accuracy of their appar- belief in ESP, there is “consistent and reliable” parapsychological phenomena is a worthy scientific ent precognitions must have seemed uncanny. evidence. Psychologist Ray Hyman (2010), who has been subject to study? Why or why not? Given the billions of events in the world each day, and given scrutinizing parapsychological research since 1957, replies that if enough days, some stunning coincidences are sure to occur. this is the best evidence, it fails to impress: “Parapsychology will Use Teacher Demonstration: ESP By one careful estimate, chance alone would predict that more achieve scientifi c acceptability only when it provides a positive Trick—Precognition (Playing Card Trick) than a thousand times a day someone on Earth will think of theory with . . . independently replicable evidence. This is from the TRM to help underline the another person and then within the next fi ve minutes will learn something it has yet to achieve after more than a century.” of that person’s death (Charpak & Broch, 2004). Thus, when Daryl Bem (2011), a respected social psychologist, has necessity for rigid experimental control explaining an astonishing event, we should “give chance a been a skeptic of stage psychics; he once quipped that “a psy- in evaluating ESP claims. chance” (Lilienfeld, 2009). With enough time and people, the chic is an actor playing the role of a psychic” (1984). Yet he has improbable becomes inevitable. reignited hopes for replicable evidence with nine experiments that seemed to show people anticipating future events. In one, TEACH “To be sure of hitting the target, shoot fi rst and call whatever you TRMTRM hit the target.” -WRITER-ARTIST ASHLEIGH BRILLIANT, 1933 Concept Connections “At the heart of science is an essential tension between two Remind students of the following con- seemingly contradictory attitudes—an openness to new ideas, no matter how bizarre or counterintuitive they may be, and the most ruthless skeptical scrutiny of all ideas, old and new.” cepts from scientifi c thinking in Unit II, “A person who talks a lot is sometimes right.” -SPANISH PROVERB -CARL SAGAN (1987) especially when considering ESP and other paranormal phenomena: PUTTING ESP TO EXPERIMENTAL TEST Correlation does not mean When faced with claims of mind reading or out - of - body travel Magician Harry Houdini after fooling Sir Arthur Conan Doyle with a pseudo-psychic trick: “Now I beg of you, Sir Arthur, causation. Just because events or communication with the dead, how can we separate bizarre ideas from those that sound strange but are true? At the heart do not jump to the conclusion that certain things you see are necessarily ‘supernatural,’ or with the work of ‘spirits,’ just occur together does not mean that of science is a simple answer: Test them to see if they work. If because you cannot explain them.” -QUOTED BY WILLIAM KALUSH AND they cause each other. they do, so much the better for the ideas. If they don’t, so much LARRY SLOMAN, THE SECRET LIFE OF HOUDINI, 2007 the better for our skepticism. Confirmation bias occurs when we only look for evidence that supports our beliefs and ignore evidence that refutes them. Many people believe in parapsychology because they rely only on the evidence that supports their beliefs. MyersAP_SE_2e_Mod17_B.indd 168 1/21/14 9:33 AM MyersAP_SE_2e_Mod17_B.indd 169 1/21/14 9:33 AM Use Teacher Demonstration: ESP Trick—Precognition (Newspaper Arti- cle Trick) from the TRM to demonstrate a simple—yet doctored—newspaper article to demonstrate precognitive abilities.

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Thinking Critically About (continued) ENGAGE

when an erotic scene was about to appear on a screen in one of TRMTRM Active Learning two randomly selected positions, Cornell University participants guessed right 53.1 percent of the time (beating 50 percent by Have students create their own a small but statistically signifi cant margin). In another, people experimental conditions under which Courtesy of Claire Cole viewed a set of words, took a recall test of those words, and they would like to test ESP. Use this then rehearsed a randomly selected subset of those words. People better remembered the rehearsed words—even when activity as a check of their knowledge the rehearsal took place after the recall test. The upcoming of research methodology learned from rehearsal—a future event—apparently affected their ability to Unit II. Use any of the following simple recall words. Bem wonders if his “anomalous” fi ndings refl ect an evolu- ESP tests from the TRM: tionary advantage to those who can precognitively anticipate Teacher Demonstration: ESP future dangers. Critics scoff. “If any of his claims were true,” wrote cognitive scientist Douglas Hofstadter (2011), “then all of Trick—Clairvoyance the bases underlying contemporary science would be toppled, Teacher Demonstration: ESP Trick— and we would have to rethink everything about the nature of the universe.” Moreover, if future events retroactively affect present Mental Telepathy (Gray Elephant in feelings, then why can’t people intuitively predict casino out- Denmark Trick) comes or stock market futures? Testing psychic powers in the British population University of Hertfordshire psychologists created a “mind machine” Teacher Demonstration: ESP Despite Bem’s research having survived critical reviews by a to see if people can infl uence or predict a coin toss (Wiseman & top-tier journal, other critics found the methods “badly fl awed” Greening, 2002). Using a touch- sensitive screen, visitors to festivals Trick—Mental Telepathy (Telephone (Alcock, 2011) or the statistical analyses “biased” (Wagenmak- around the country were given four attempts to call heads or tails. Book Trick) ers et al., 2011). “A result—especially one of this importance— Using a random-number generator, a computer then decided the outcome. When the experiment concluded in January 2000, nearly must recur several times in tests by independent and skeptical 28,000 people had predicted 110,959 tosses—with 49.8 percent researchers to gain scientifi c credibility,” observed astronomer correct. CLOSE & ASSESS David Helfand (2011). “I have little doubt that Professor Bem’s experiments will fail this test.” one need only produce a single person who can demonstrate Exit Assessment Anticipating such skepticism, Bem has made his computer a single, reproducible ESP event. (To refute those who say pigs Provide students with the following materials available to anyone who wishes to replicate his stud- can’t talk would take but one talking pig.) So far, no such person ies, and replications are now under way. One research team has has emerged. scenario (or a similar one of your own already conducted fi ve replications of Bem’s recall experiments choosing): at various universities and found no precognition (Galak et al., You are enjoying dinner with your 2011). Regardless of the outcomes, science will have done its Before You Move On work. It will have been open to a fi nding that challenges its own family at a local restaurant. A large worldview, and then, through follow-up research, it will have as- ᭤ ASK YOURSELF group of people, both male and sessed its validity. And that is how science sifts crazy-sounding Have you ever had what felt like an ESP experience? female, enters the restaurant sing- ideas, leaving most on the historical waste heap while occa- Can you think of an explanation other than ESP for that sionally surprising us. ing and talking loudly. The people experience? One skeptic, magician James Randi, has had a longstand- continue to speak and sing loudly ing offer of $1 million to be given “to anyone who proves a genu- ᭤ TEST YOURSELF throughout their time in the res- ine psychic power under proper observing conditions” (Randi, What is the fi eld of study that researches claims of taurant. How do you perceive this 1999; Thompson, 2010). French, Australian, and Indian groups extrasensory perception (ESP)? have made similar offers of up to 200,000 euros (CFI, 2003). situation and explain this group’s Answers to the Test Yourself questions can be found in Ap- Large as these sums are, the scientifi c seal of approval would pendix E at the end of the book. behavior? Use your knowledge of be worth far more. To refute those who say there is no ESP, expectations/set, context, emotions, and motivations to craft your answer. Use students’ explanations to determine how well they understand the concepts in this module.

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Module 17 Review How do our expectations, contexts, 17-117-1 17-217-2 What are the claims of ESP, and what have emotions, and motivation infl uence our most research psychologists concluded perceptions? after putting these claims to the test?

• Perceptual set is a mental predisposition that functions as a • Parapsychology is the study of paranormal phenomena, lens through which we perceive the world. including extrasensory perception (ESP) and psychokinesis. • Our learned concepts (schemas) prime us to organize and • The three most testable forms of ESP are telepathy (mind- interpret ambiguous stimuli in certain ways. to-mind communication), clairvoyance (perceiving remote events), and precognition (perceiving future events). • Our physical and emotional context, as well as our motivation, can create expectations and color our • Skeptics argue that (1) to believe in ESP, you must believe interpretation of events and behaviors. the brain is capable of perceiving without sensory input, and (2) researchers have been unable to replicate ESP phenomena under controlled conditions. Answers to Multiple-Choice Multiple-Choice Questions

Questions 1. What do we call a mental predisposition that inﬂ uences 3. Which of the following is produced by perceptual set? our interpretation of a stimulus? a. Not noticing that the songs change in a restaurant 1. b 3. d a. A context effect b. Noticing a difference in the weight of a friend from 2. a b. Perceptual set one week to the next c. Extrasensory perception c. Moving an arm quickly so that a mosquito ﬂ ies away d. Emotion d. Surprise at hearing an Oklahoma cowboy speak with e. Motivation a British accent e. Not noticing a watch on your wrist as the day 2. Kimberly tells her brother to put on a suit on a warm goes on summer day. Kimberly’s brother knows to put on a swimsuit instead of a business suit because of a. context. b. ESP. c. precognition. d. bottom-up processing. e. clairvoyance.

Answer to Practice FRQ 2 Practice FRQs 1. 1 point: 1 point: Context eff ects: Environmen- Martha is convinced she has extrasensory perception. Clairvoyance: Martha would be able to perceive things Explain what Martha’s specifi c abilities would be if she happening at a distance; that is, a cousin who lives in another tal factors can infl uence perception. had each of the following forms of ESP: state just burnt her hand on the oven, and Martha feels it. For example, a tall basketball player • Telepathy 1 point: Precognition: Martha would be able to see future might look short when standing next • Clairvoyance events happen; that is, she knows a pop quiz will take place to a much taller player. • Precognition next week. Then, briefl y explain why you should doubt her claims. 1 point: There has never been a conclusive scientifi c 1 point: Emotion: Mood can infl uence Answer demonstration of extrasensory ability. perception. For example, happy or sad 2. 1 point: Telepathy: Martha would be able to use mind-to- How can context effects, emotions, and motivation music can alter one’s perception of mind communication; that is, she is able to read someone’s trigger different perceptions of a single stimulus? ambiguous words and scenes. mind. (3 points) 1 point: Motivation: Motivation can infl uence perception. For example, a water bottle can seem closer when one

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TEACH Module 18 TRMTRM Discussion Starter Use the Module 18 Fact or Falsehood?

rbis student activity from the TRM to intro- Vision duce the concepts from this module.

© Randy Lincks/Corbis Randy © ENGAGE Module Learning Objectives Online Activities 18-118-1 Describe the characteristics of visible light, and explain the process by which the eye transforms light energy into neural Vision Science is a site that provides messages. recent research and activities related to human and animal visual sys- 18-2 Describe how the eye and brain process visual information. tems. Use the following website to 18-318-3 Discuss the theories that help us understand color vision. enhance students’ understanding of our visual system: Vision Science at

wavelength the distance from the peak of one light http://visionscience.com. or sound wave to the peak of the next. Electromagnetic wavelengths vary from the short blips of cosmic rays to 18-118-1 What is the energy that we see as visible light, and how does the eye the long pulses of radio transmission. TEACH transform light energy into neural Figure 18.1 messages? Interdisciplinary The wavelengths we Our eyes receive light energy and transduce (trans- see What we see as Connections light is only a tiny slice form) it into neural messages that our brain then of a wide spectrum of Team with your school’s physics processes into what we consciously see. How does White electromagnetic energy, light such a taken- for - granted yet remarkable thing Prism which ranges from instructor to give a lesson on the happen? gamma rays as short as the diameter of an atom physics of light. Light is an interesting to radio waves over a mile phenomenon that behaves both like long. The wavelengths The Stimulus Input: visible to the human eye waves and like particles. Our ability (shown enlarged) extend Light Energy from the shorter waves to see color depends on the wave of blue -violet light to the When you look at a bright red tulip, what strikes longer waves of red light. properties of light. Objects reﬂ ect the your eyes is not particles of the color red but pulses of electromagnetic energy that your visual system wavelength of their colors back to the perceives as red. What we see as visible light is eye and absorb all other wavelengths but a thin slice of the whole spectrum of electro- of light. A possible guest speaker for magnetic energy, ranging from imperceptibly short 400 500 600 700 gamma waves to the long waves of radio transmis- this lesson could be an astrophysicist, Part of spectrum visible sion (FIGURE 18.1). Other organisms are sensitive to humans who might address such issues as to differing portions of the spectrum. Bees, for in- how astrophysicists use the properties stance, cannot see what we perceive as red but can see ultraviolet light. Gamma X-rays Ultra- Infrared Radar Broadcast of light to determine the age of the rays violet rays bands Two physical characteristics of light help deter- rays universe. mine our sensory experience of them. Light’s wave- 10–5 10–3 10–1 101 103 105 107 109 1011 1013 length—the distance from one wave peak to the next Wavelength in nanometers (billionths of a meter)

MyersAP_SE_2e_Mod17_B.indd 170 1/21/14 9:33 AM MyersAP_SE_2e_Mod18_B.indd TEACH 171 1/21/14 9:33 AM Teaching Tip Have students draw, with the appropriate colored crayon, what the diﬀ erent wavelengths of light would look like. For instance, a bright red color would have a long wavelength, one with a great (tall) amplitude, whereas a dull blue color would have a short wavelength with a small (short) amplitude. Have them consult a physics textbook or search online for help with the colors between red and blue. Students with learning diﬃ culties might appreciate this more tactile approach to understanding the relationship between colors and wavelength.

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TEACH Figure 18.2 Short wavelength = high frequency Great amplitude The physical properties of (bluish colors; high-pitched sounds) (bright colors; loud sounds) Common Pitfalls waves (a) Waves vary in wavelength (the distance between successive Vision and audition use similar terms peaks). Frequency, the number of complete wavelengths that can pass to discuss the diff erent stimuli that are a point in a given time, depends on the wavelength. The shorter the processed by our visual and auditory wavelength, the higher the frequency. Long wavelength = low frequency Small amplitude Wavelength determines the perceived (reddish colors; low-pitched sounds) (dull colors; quiet sounds) systems. This is because both visual color of light (and also the pitch and auditory stimuli work in waves, so of sound). (b) Waves also vary in amplitude (the height from peak to the characteristics of waves are similar trough). Wave amplitude determines the brightness of colors (and also the for both light and sound. (For more on loudness of sounds). (a) (b) sound waves, see Module 20. ) hue the dimension of color that FIGURE 18.2a hue Wavelength determines the quality ( )—determines its (the color we experience, such as the tulip’s red petals is determined by the wavelength or green leaves). Intensity, the amount of energy in light waves (determined by a wave’s of the waves (for vision, color; for of light; what we know as the color names blue, green, and so forth. amplitude, or height), infl uences brightness (Figure 18.2b). To understand how we transform physical energy into color and meaning, we fi rst need to understand vision’s window, the eye. sound, pitch) intensity the amount of energy Amplitude determines the intensity in a light or sound wave, which we perceive as brightness or loudness, The Eye of the waves (for vision, brightness; as determined by the wave’s amplitude. for sound, loudness) Light enters the eye through the cornea, which protects the eye and bends light to provide pupil the adjustable opening in focus (FIGURE 18.3). The light then passes through the pupil, a small adjustable opening. the center of the eye through which Surrounding the pupil and controlling its size is the iris, a colored muscle that dilates or light enters. TEACH constricts in response to light intensity and even to inner emotions. (When we’re feeling iris a ring of muscle tissue that amorous, our telltale dilated pupils and dark eyes subtly signal our interest.) Each iris is so forms the colored portion of the eye distinctive that an iris-scanning machine can confi rm your identity. Interdisciplinary around the pupil and controls the size of the pupil opening. Behind the pupil is a lens that focuses incoming light rays into an image on the retina, Connections a multilayered tissue on the eyeball’s sensitive inner surface. The lens focuses the rays by lens the transparent structure accommodation. Invite your school’s art or photography behind the pupil that changes shape changing its curvature in a process called to help focus images on the retina. For centuries, scientists knew that when an image of a candle passes through a small teacher to explain how a camera is sim- retina the light - sensitive inner opening, it casts an inverted mirror image on a dark wall behind. If the retina receives this ilar to the eye. Cameras use the eye as surface of the eye, containing sort of upside - down image, as in Figure 18.3, how can we see the world right side up? a model for how much light to let in to the receptor rods and cones plus The ever - curious Leonardo da Vinci had an idea: Perhaps the eye’s watery fl uids bend the layers of neurons that begin the light rays, reinverting the image to the upright position as it reaches the retina. But then in create a correct photograph of a given processing of visual information. 1604, the astronomer and optics expert Johannes Kepler showed that the retina does receive image or situation. Have the teacher accommodation the process by upside - down images of the world (Crombie, 1964). And how could we understand such a which the eye’s lens changes shape to world? “I leave it,” said the befuddled Kepler, “to natural philosophers.” cover any of the following topics: focus near or far objects on the retina. Why certain film is important to use Figure 18.3 for different situations and images Lens Retina The eye Light rays reflected from a candle pass through the cornea, pupil, Pupil Why a flash is important and when and lens. The curvature and thickness it should be used of the lens change to bring nearby Fovea or distant objects into focus on the (point of Creative ways photographers retina. Rays from the top of the candle central focus) strike the bottom of the retina, and use the camera’s features to take those from the left side of the candle strike the right side of the retina. The Iris candle’s image on the retina thus © Pascal Goetgheluck/ Optic nerve interesting pictures Science Source appears upside down and reversed. Cornea to brain’s visual cortex Blind spot

MyersAP_SE_2e_Mod18_B.inddTEACH 172 1/21/14 9:33 AM MyersAP_SE_2e_Mod18_B.indd 173 1/21/14 9:33 AM Common Pitfalls The word accommodation means diﬀ erent things in diﬀ erent contexts. For this unit, accommodation means the ways in which the muscles of the eye change the shape of the lens to focus light onto the retina. In Unit IX, accommodation means the ways in which we change our schemas to incorporate new information we learn.

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AP® Exam Tip Eventually, the answer became clear: The retina doesn’t “see” a whole image. Rather, ENGAGE its millions of receptor cells convert particles of light energy into neural impulses and There’s a lot of vocabulary here. forward those to the brain. There, the impulses are reassembled into a perceived, upright- Make sure you understand the seeming image. name and the function of each of Active Learning the parts of the eye. To learn how all the parts fi t together, it may help Nearsightedness occurs when the lens The Retina to make rough sketches (you don’t need to be an artist to try this!) focuses objects in front of the retina. If you could follow a single light-energy particle into your eye, you would fi rst make your and then compare your sketches way through the retina’s outer layer of cells to its buried receptor cells, the rods and with Figures 18.3 and 18.4. You’ll Farsightedness occurs when the lens cones (FIGURE 18.4). There, you would see the light energy trigger chemical changes be better off making several quick, focuses objects behind the retina. rough sketches than one time- that would spark neural signals, activating nearby bipolar cells. The bipolar cells in turn consuming, nicely drawn one. Using an overhead projector, have stu- would activate the neighboring ganglion cells, whose axons twine together like the strands of a rope to form the optic nerve. That nerve will carry the information to your brain, dents imagine the screen is the retina. where your thalamus stands ready to distribute the information. The optic nerve can send rods retinal receptors that detect When the projector is blurred in either nearly 1 million messages at once through its nearly 1 million ganglion fi bers. (The audi- black, white, and gray; necessary direction, you have to move the projec- tory nerve, which enables hearing, carries much less information through its mere 30,000 for peripheral and twilight vision, fi bers.) We pay a small price for this eye-to-brain highway. Where the optic nerve leaves when cones don’t respond. tor or the screen in order to focus it. the eye, there are no receptor cells—creating a blind spot (FIGURE 18.5 on the next cones retinal receptor cells that page). Close one eye and you won’t see a black hole, however. Without seeking your ap- are concentrated near the center proval, your brain fi lls in the hole. of the retina and that function in ENGAGE Rods and cones differ in where they’re found and in what they do (TABLE 18.1 on the daylight or in well - lit conditions. The cones detect fi ne detail and next page). Cones cluster in and around the fovea, the retina’s area of central focus (see Fig- TRMTRM Enrichment give rise to color sensations. ure 18.3). Many have their own hotline to the brain: Each one transmits to a single bipolar optic nerve the nerve that carries What is red eye, that annoying red cell that helps relay the cone’s individual message to the visual cortex, which devotes a large neural impulses from the eye to the dot that appears in people’s eyes in area to input from the fovea. These direct connections preserve the cones’ precise informa- brain. tion, making them better able to detect fi ne detail. blind spot the point at which the pictures, and why does it occur? Usu- Rods have no such hotline; they share bipolar cells with other rods, sending combined optic nerve leaves the eye, creating ally, red eye occurs in pictures where messages. To experience this rod-cone difference in sensitivity to details, pick a word in this a “blind” spot because no receptor sentence and stare directly at it, focusing its image on the cones in your fovea. Notice that cells are located there. the surrounding illumination is dim, fovea the central focal point in so the camera’s fl ash must be used to the retina, around which the eye’s cones cluster. take an accurate picture. The fl ash is so 2. Chemical reaction in turn Figure 18.4 activates bipolar cells. quick that the iris doesn’t have time to 1. Light entering eye triggers The retina’s 3 reaction to light photochemical reaction in rods 2 contract, making the pupil big enough and cones at back of retina. 1 to see right through to the red retina! Light Cameras with so-called “red-eye reduc- Cone tion” features provide a series of quick Rod Ganglion fl ashes that warn the eye that a picture cell Bipolar is about to be taken. The iris reacts to cell Neural impulse the light pulses and shrinks the pupil Light 3 so that the retina is protected from the

2 bright ﬂ ash. Use Student Activity: Locating the 1 Retinal Blood Vessels from the TRM to Cross section of retina Optic nerve To the brain’s visual demonstrate properties of the retina. cortex via the thalamus

3. Bipolar cells then activate the ganglion cells, the axons of which converge to form the optic nerve. This nerve transmits information to the visual cortex (via the thalamus) in the brain. ENGAGE Applying Science Have students conduct an experiment to see which type of red-eye reduction fl ash leads to the lowest amount of red MyersAP_SE_2e_Mod18_B.indd 172 1/21/14 9:33 AM MyersAP_SE_2e_Mod18_B.inddENGAGE 173 1/21/14 9:33 AM eye in a picture. Be sure they include Active Learning students who have both light colored eyes and darker colored eyes to control Have students test their foveal vision in the look at the image in their peripheral vision, for eye color. See Module 2 for a discus- dark as a homework project. Have them go in focusing their foveal vision just to the side of sion of diff erent research methods to their backyards or in a darkened room (with the object they want to see. They should note use for this type of study. light only from ambient sources) and try to that the object becomes clearer and more focus their central vision on an object in the detailed when they don’t look at it directly, environment. They should refl ect on how because in dim light the cones in the fovea are detailed the object appears. Then, have them not activated but the rods in the periphery are.

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ENGAGE Figure 18.5 The blind spot There are no receptor cells where the optic nerve leaves the eye. This creates a blind Active Learning spot in your vision. To demonstrate, first close your left eye, look at the spot, and move the page to a Extend the text’s blind-spot activity by distance from your face at which one of the cars having students notice what exactly disappears (which one do you predict it will be?). Repeat with the other eye closed—and note that ﬁ lls the space where the blind spot is. now the other car disappears. Can you explain why? The space is actually white, not gray or black as one would expect. Students words a few inches off to the side appear blurred? Their image strikes the outer regions of your retina, where rods predominate. Thus, when driving or biking, you can detect a car in can even draw a line around the car. your peripheral vision well before perceiving its details. This time they will notice the line Cones also enable you to perceive color. In dim light they become ineffectual, so you see continues as the brain creates what ﬁ lls no colors. Rods, which enable black - and - white vision, remain sensitive in dim light. Several rods will funnel their faint energy output onto a single bipolar cell. Thus, cones and rods the blind spot based on the surround- each provide a special sensitivity—cones to detail and color, and rods to faint light. ing stimuli. Table 18.1 Receptors in the Human ENGAGE Eye: Rod-Shaped Rods and Cone - Shaped Cones

Enrichment Cones Rods Omikron/Science Source

By deliberately aiming the blind spot, Number 6 million 120 million

one can block out any appropriately Location in retina Center Periphery

sized object. Legend has it that King Sensitivity in dim light Low High

Charles II of England did this with Color sensitivity High Low

his courtiers. V. S. Ramachandran Detail sensitivity High Low reported, “He used to make their heads

disappear. One story is that he used to When you enter a darkened theater or turn off the light at night, your eyes adapt. Your do it to people he had sentenced to pupils dilate to allow more light to reach your retina, but it typically takes 20 minutes or die, to see what they would look like more before your eyes fully adapt. You can demonstrate dark adaptation by closing or cover- ing one eye for up to 20 minutes. Then make the light in the room not quite bright without their heads.” enough to read this book with your open eye. Now open the dark- adapted eye and read (easily). This period of dark adaptation matches the average natural twilight transition between the Sun’s setting and darkness. How wonderfully TEACH Andrey Armyagov /Shutterstock made we are. Flip It Students can get some additional help Visual Information Processing understanding the role of rods and 18-218-2 How do the eye and the brain process visual information? cones by watching the Flip It Video: Visual information percolates through progressively more abstract levels on its path Rods and Cones in the Retina. through the thalamus and on to the visual cortex. At the entry level, information processing begins in the retina’s neural layers, which are actually brain tissue that has migrated to the eye during early fetal development. These layers don’t just pass along electrical impulses; they also help to encode and analyze sensory information. The third neural layer in a frog’s eye, for example, contains the “bug detector” cells that ﬁ re only in response to moving ﬂ y-like stimuli.

ENGAGEMyersAP_SE_2e_Mod18_B.indd 174 1/21/14 9:33 AM MyersAP_SE_2e_Mod18_B.indd 175 1/21/14 9:33 AM Active Learning Because cones detect color and rods do not, Move in a semicircle toward the student’s cen- students might not realize that their peripheral ter of vision, asking periodically if the student vision is very poor at judging color. Have a stu- can tell what color the marker is. Repeated dent sit in a chair and ﬁ xate on a point straight guessing will prove incorrect until the marker is ahead. Stand to the side of the student, at a close to the center of the ﬁ eld of vision where 180° angle, with a colored marker or piece of the cones reside. colored paper against a neutral background.

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After processing by your retina’s nearly 130 million receptor rods and cones, informa- TEACH tion travels to your bipolar cells, then to your million or so ganglion cells, and through their axons making up the optic nerve to your brain. Any given retinal area relays its information Common Pitfalls to a corresponding location in the visual cortex, in the occipital lobe at the back of your brain (FIGURE 18.6). The cells that make up the retina seem The same sensitivity that enables retinal cells to fi re messages can lead them to misfi re, backward. The rods and cones are as you can demonstrate for yourself. Turn your eyes to the left, close them, and then gently rub the right side of your right eyelid with your fi ngertip. Note the patch of light to the left, located at the very back of the retina. moving as your fi nger moves. Why do you see light? Why at the left? The bipolar and ganglion cells are Your retinal cells are so responsive that even pressure triggers them. But your brain stacked on top of the rods and cones in interprets their fi ring as light. Moreover, it interprets the light as coming from the left—the normal direction of light that activates the right side of the retina. layers. The rods and cones interpret the light fi rst, even though the light passes Figure 18.6 through the bipolar and ganglion cells Visual area of the thalamus Pathway from the eyes to the visual cortex Ganglion axons before it hits those light-sensitive cells. forming the optic nerve run to the Optic thalamus, where they synapse with nerve neurons that run to the visual cortex. TEACH Concept Connections

Retina Connect this topic to neuroscience in Unit III by reminding students that visual processing occurs in the occipital lobe of the brain rather than in the eye. Visual cortex The occipital lobe is located in the back of the brain, just above the cerebellum. Students can look back at Figures 12.1, 12.5, and 12.6 as a refresher.

TEACH Feature Detection Flip It feature detectors nerve cells in David Hubel and Torsten Wiesel (1979) received a Nobel Prize for their work on feature Students can get some additional help detectors. These specialized neurons in the occipital lobe’s visual cortex receive infor- the brain that respond to speciﬁ c features of the stimulus, such as mation from individual ganglion cells in the retina. Feature detector cells derive their understanding how feature detectors shape, angle, or movement. name from their ability to respond to a scene’s speciﬁ c features—to particular edges, lines, work by watching the Flip It Video: angles, and movements. These cells pass this information to other cortical areas, where teams of cells (supercell clusters) respond to more complex patterns. As we noted in Mod- Feature Detectors. ule 12, one temporal lobe area by your right ear (FIGURE 18.7 on the next page) enables you to perceive faces and, thanks to a specialized neural network, to recognize them from AP® Exam Tip varied viewpoints (Connor, 2010). If this region were damaged, you might recognize other forms and objects, but, like Heather Sellers, not familiar faces. When researchers tempo- Warning! Sometimes students spend so much time mastering rarily disrupt the brain’s face-processing areas with magnetic pulses, people are unable to the parts of the eye that they recognize faces. skim over the part you’re about to They will, however, be able to recognize houses, because the brain’s face-perception read. Do not forget that you see occurs separately from its object-perception (McKone et al., 2007; Pitcher et al., 2007). with your brain as much as you see with your eyes. Thus, functional MRI (fMRI) scans show different brain areas activating when people

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Figure 18.7 Face recognition processing In social animals such as humans, a dedicated brain system (shown here in a right-facing brain) assigns considerable neural bandwidth to the crucial task of face recognition.

Face recognition area

view varied objects (Downing et al., 2001). Brain activity is so specifi c (FIGURE 18.8) that, with the help of brain scans, “we can tell if a person is looking at a shoe, a chair, or a face, based on the pattern of their brain Figure 18.8 activity,” noted one researcher (Haxby, 2001). The telltale brain Looking at faces, Research shows that for biologically important objects and events, monkey brains (and houses, and chairs activates different surely ours as well) have a “vast visual encyclopedia” distributed as specialized cells (Perrett brain areas in this right-facing brain. et al., 1988, 1992, 1994). These cells respond to one type of stimulus, such as a specifi c gaze, head angle, posture, or body movement. Other supercell clusters integrate this information and fi re only when the cues collectively indicate the direction of someone’s attention and approach. This instant analysis, which aided our ancestors’ survival, also helps a soccer goalkeeper anticipate the direction of an impending kick, and a driver anticipate a pedestrian’s next movement. FIFA via Getty Images FIFA

Well - developed supercells In this 2011 World Cup match, USA’s Abby Wambach instantly processed visual information about the positions and movements of Brazil’s defenders and goalkeeper and somehow managed to get the ball around them all and into the net.

TEACH parallel processing the processing of many aspects of Parallel Processing Concept Connections a problem simultaneously; the brain’s natural mode of information Our brain achieves these and other remarkable feats by means of parallel processing: do- Remind students that the human brain processing for many functions, ing many things at once. To analyze a visual scene, the brain divides it into subdimensions— including vision. Contrasts with the is uniquely capable of parallel process- step - by - step (serial) processing of motion, form, depth, color—and works on each aspect simultaneously (Livingstone & Hubel, ing, as discussed in Unit III. Computers most computers and of conscious 1988). We then construct our perceptions by integrating the separate but parallel work of these problem solving. different visual teams (FIGURE 18.9). process serially, only able to do one process at a time. Humans can process multiple types of stimuli from the environment, making us more eﬃ cient in understanding the world than com- MyersAP_SE_2e_Mod18_B.indd 176 1/21/14 9:33 AM MyersAP_SE_2e_Mod18_B.indd 177 1/21/14 9:33 AM puters. In fact, our visual system is so adept at parallel processing and, thus, so complicated, that no computer has been invented that can re-create it.

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Figure 18.9 ENGAGE Motion Form Depth Color Parallel processing Studies of patients with brain damage suggest that Enrichment the brain delegates the work of processing motion, form, depth, and color to different Those with blindsight, argues Anthony areas. After taking a scene apart, the brain integrates these subdimensions into the Marcel of Cambridge University, have perceived image. How does the brain do this? The answer to this question is the superb vision but they don’t know Holy Grail of vision research. they can see. Employing a high-speed camera, Marcel tracked the arms,

To recognize a face, your brain integrates information projected by your retinas to sev- hands, and fi ngers of individuals with eral visual cortex areas, compares it with stored information, and enables you to recognize blindsight as they reached for objects the face: Grandmother! Scientists are debating whether this stored information is contained they could not consciously see. The in a single cell or distributed over a network. Some supercells—“grandmother cells”—do appear to respond very selectively to 1 or 2 faces in 100 (Bowers, 2009). The whole facial fi lms indicate that their reach was quite recognition process requires tremendous brain power—30 percent of the cortex (10 times precise. This suggests that their vision the brain area devoted to hearing). Destroy or disable a neural workstation for a visual subtask, and something peculiar remains intact; only the neural areas results, as happened to “Mrs. M.” (Hoffman, 1998). Since a stroke damaged areas near the that bring vision into awareness are rear of both sides of her brain, she has been unable to perceive movement. People in a room impaired. seem “suddenly here or there but I have not seen them moving.” Pouring tea into a cup is a challenge because the fl uid appears frozen—she cannot perceive it rising in the cup. After stroke or surgery damage to the brain’s visual cortex, others have experienced blind- ENGAGE sight (a phenomenon we met in Module 13). Shown a series of sticks, they report seeing nothing. Yet when asked to guess whether the sticks are vertical or horizontal, their visual intuition typi- Online Activities cally offers the correct response. When told, “You got them all right,” they are astounded. There is, it seems, a second “mind”—a parallel processing system—operating unseen. These separate Blindsight occurs when people experi- visual systems for perception and action illustrate dual processing—the two-track mind. ence damage to the visual cortex of the * * * brain. Their eyes are fully functioning, Think about the wonders of visual processing. As you look at that tiger in the zoo, informa- “I am . . . wonderfully made.” -KING DAVID, PSALM 139:14 but they report they cannot see even tion enters your eyes, is transduced, and is sent to your brain as millions of neural impulses. As your brain buzzes with activity, various areas focus on different aspects of the tiger’s im- when they demonstrate that they can. age. Finally, in some as yet mysterious way, these separate teams pool their work to produce For an interesting demonstration of a meaningful image, which you compare with previously stored images and recognize: a blindsight, as well as additional descrip- crouching tiger (FIGURE 18.10). tion of the phenomenon, have students visit the Serendip Brain and Behavior Figure 18.10 A simplified summary of visual site at http://serendip.brynmawr.edu/ information processing bb/blindsight.html. Tom Walker/Getty Images Walker/Getty Tom

Parallel processing: Feature detection: Recognition: Retinal processing: Brain cell teams Brain’s detector cells Brain interprets the Scene Receptor rods and process combined cones bipolar cells respond to specific information about constructed image ganglion cells features—edges, lines, motion, form, based on information and angles depth, color from stored images

MyersAP_SE_2e_Mod18_B.indd 176 1/21/14 9:33 AM MyersAP_SE_2e_Mod18_B.indd TEACH 177 1/21/14 9:33 AM Teaching Tip Discuss Figure 18.10 to show how much work goes into processing a simple visual image. The complexity of this process is still fascinating to researchers.

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TEACH Think, too, about what is happening as you read this page. The printed squiggles are transmitted by reﬂ ected light rays onto your retina, which triggers a process that sends TRMTRM Common Pitfalls formless nerve impulses to several areas of your brain, which integrates the information and decodes meaning, thus completing the transfer of information across time and space from Students often ask, “How do I know my mind to your mind. That all of this happens instantly, effortlessly, and continuously is I am seeing the same color as some- indeed awesome. As Roger Sperry (1985) observed, the “insights of science give added, not lessened, reasons for awe, respect, and reverence.” one else?” The answer is simple: The wavelength of light determines the Color Vision color, so in a properly functioning eye and brain, the color will be processed 18-318-3 What theories help us understand color vision?

the same. However, what we call color We talk as though objects possess color: “A tomato is red.” Perhaps you have pondered the shades can vary signifi cantly, espe- old question, “If a tree falls in the forest and no one hears it, does it make a sound?” We can cially in advertising. Acquire several ask the same of color: If no one sees the tomato, is it red? The answer is No. First, the tomato is everything but red, because it rejects (refl ects) the catalogues of clothing companies long wavelengths of red. Second, the tomato’s color is our mental construction. As Isaac New- or go to their websites and compare ton (1704) noted, “The [light] rays are not colored.” Color, like all aspects of vision, resides not what they call similar hues of color for in the object but in the theater of our brain, as evidenced by our dreaming in color. “Only mind has sight and hearing; One of vision’s most basic and intriguing mysteries is how we see the world in color. clothes they sell. Are forest and hunter all things else are deaf and blind.” How, from the light energy striking the retina, does the brain manufacture our experience -EPICHARMUS, FRAGMENTS, 550 B.C.E. the same shade of green? Students can of color—and of such a multitude of colors? Our difference threshold for colors is so low that we can discriminate more than 1 million different color variations (Neitz et al., 2001). also make a list of the diff erent names At least most of us can. For about 1 person in 50, vision is color defi cient—and that person for hues in the same color family (reds, is usually male, because the defect is genetically sex-linked. blues, greens, browns, etc.). Use Stu- Why is some people’s vision defi cient? To answer that question, we need to understand how normal color vision works. Modern detective work on this mystery began dent Activity: Subjective Colors from in the nineteenth century, when Hermann von Helmholtz built on the insights of an Young - Helmholtz trichromatic English physicist, Thomas Young. Knowing that any color can be created by combining the TRM to demonstrate color vision (three - color) theory the theory the light waves of three primary colors—red, green, and blue—Young and von Helm- illusions. that the retina contains three different color receptors—one most holtz inferred that the eye must have three corresponding types of color receptors. Years sensitive to red, one to green, one later, researchers measured the response of various cones to different color stimuli and TEACH to blue—which, when stimulated confi rmed the Young- Helmholtz trichromatic (three - color) theory, which implies in combination, can produce the that the receptors do their color magic in teams of three. Indeed, the retina has three Common Pitfalls perception of any color. types of color receptors, each especially sensitive to one of three colors. And those colors are, in fact, red, green, and blue. When we stimu- Students have a hard time accepting late combinations of these cones, we see other colors. that both theories of color vision are Figure 18.11 For example, there are no receptors especially sensitive Color-deficient to yellow. We see yellow when mixing red and green likely correct. Because visual process- vision People who suffer red- green deficiency have light, which stimulates both red -sensitive and green - ing occurs in both the eye and the trouble perceiving the number sensitive cones. brain, both theories of color vision within the design. Most people with color - defi cient vision are not ac-

Annabella Bluesky/Science Source tually “colorblind.” They simply lack functioning red- or may work in each context. However, green- sensitive cones, or sometimes both. Their vision— testing these theories in humans is not perhaps unknown to them, because their lifelong vision currently possible, because we do not seems normal—is monochromatic (one-color) or dichro- matic (two- color) instead of trichromatic, making it im- possess the technology to study the possible to distinguish the red and green in FIGURE retina in action. 18.11 (Boynton, 1979). Dogs, too, lack receptors for the wavelengths of red, giving them only limited, dichromat- ic color vision (Neitz et al., 1989). ENGAGE TRMTRM Enrichment People who are color blind see the color they are defi cient in as a shade of muted gray or brown. They’ve been ENGAGEMyersAP_SE_2e_Mod18_B.indd 178 TEACH 1/23/14 1:57 PM MyersAP_SE_2e_Mod18_B.indd 179 1/21/14 9:33 AM trained, however, to identify that Interdisciplinary Connections muted “color” as red, blue, or green Online Activities Team teach a lesson in subtractive and additive (depending on their defi ciency), so Have students experience color blindness by color mixing with your school’s art teacher. unless tested, they usually do not accessing the following websites: Encourage students to combine colors in know they are color blind! Use Student www.neitzvision.com/content/ diff erent levels to create some of the 7 million Activity: The Color Vision Screening colorblindworld.html. diff erent hues the human eye can see. Inventory and Color Blindness from www.etre.com/tools/colourblindsimulator/. the TRM to assess color blindness www.colourblindawareness.org/colour- in students. blindness/colour-blindness-experience-it/.

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Figure 18.12 ENGAGE Afterimage effect Stare at the center of the flag for a minute and TRMTRM Online Activities then shift your eyes to the dot in the white space beside it. What do Afterimages are not limited to color you see? (After tiring your neural response to black, green, and yellow, vision. Students can see afterimages of you should see their opponent colors.) Stare at a white wall and note movement as well. For a vivid example how the size of the flag grows with the projection distance. of movement aftereff ects, invite students to visit http://dogfeathers.com/ But how is it that people blind to red and green can often still see yellow? And why does java/spirals.html. They will view the yellow appear to be a pure color and not a mixture of red and green, the way purple is of red and blue? As Ewald Hering soon noted, trichromatic theory leaves some parts of the color Counter-Rotating Spirals illusion and vision mystery unsolved. learn more of the history of motion Hering, a physiologist, found a clue in afterimages. Stare at a green square for a while and then look at a white sheet of paper, and you will see red, green’s opponent color. Stare at aftereff ects. Use Teacher Demonstra- a yellow square and its opponent color, blue, will appear on the white paper. (To experience tion: Movement Aftereff ects from this, try the fl ag demonstration in FIGURE 18.12.) Hering surmised that there must be two the TRM for another example to use additional color processes, one responsible for red- versus - green perception, and one for blue - versus - yellow. with students. Indeed, a century later, researchers also confi rmed Hering’s opponent -process theory. opponent - process theory Three sets of opponent retinal processes—red-green, yellow-blue, and white-black—enable col- the theory that opposing retinal or vision. In the retina and in the thalamus (where impulses from the retina are relayed en processes (red - green, yellow - blue, TEACH white - black) enable color vision. For route to the visual cortex), some neurons are turned “on” by red but turned “off” by green. example, some cells are stimulated Concept Connections Others are turned on by green but off by red (DeValois & DeValois, 1975). Like red and green by green and inhibited by red; marbles sent down a narrow tube, “red” and “green” messages cannot both travel at once. So others are stimulated by red and Opponent processes occur in many we do not experience a reddish green. (Red and green are thus opponents.) But red and blue inhibited by green. diff erent contexts. Here, in Unit IV, the travel in separate channels, so we can see a reddish-blue magenta. So how do we explain afterimages, such as in the fl ag demonstration? By staring at perception of color operates as an green, we tire our green response. When we then stare at white (which contains all colors, opponent process as one color works including red), only the red part of the green - red pairing will fi re normally. The present solution to the mystery of color vision is therefore roughly this: Color pro- only when the other color does not. In cessing occurs in two stages. The retina’s red, green, and blue cones respond in varying Unit III, the sympathetic and parasym- degrees to different color stimuli, as the Young- Helmholtz trichromatic theory suggested. pathetic nervous systems work as an Their signals are then processed by the nervous system’s opponent - process cells, as Her- ing’s theory proposed. opponent process. When one system is active, the other is not. Before You Move On CLOSE & ASSESS ᭤ ASK YOURSELF If you were forced to give up one sense, which would it be? Why? Exit Assessment ᭤ TEST YOURSELF Provide students with a diagram of What is the rapid sequence of events that occurs when you see and recognize a friend? the eye (such as Figure 18. 3) and have Answers to the Test Yourself questions can be found in Appendix E at the end of the book. them label the diagram with the correct parts of the eye. Also have them explain the function of each part, making sure students know how light is received by the eye and transferred to the brain for processing.

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Module 18 Review What is the energy that we see as visible 18-1 18-318-3 What theories help us understand color light, and how does the eye transform light vision? energy into neural messages? • The Young-Helmholtz trichromatic (three-color) theory • The hue we perceive in light depends on its wavelength, proposed that the retina contains three types of color and its brightness depends on its intensity. receptors. Contemporary research has found three types of cones, each most sensitive to the wavelengths of one of After entering the eye and being focused by the lens, light • the three primary colors of light (red, green, or blue). energy particles (from a thin slice of the broad spectrum of electromagnetic energy) strike the eye’s inner surface, the • Hering’s opponent-process theory proposed three additional retina. The retina’s light-sensitive rods and color-sensitive color processes (red-versus-green, blue-versus-yellow, cones convert the light energy into neural impulses. black-versus-white). Contemporary research has conﬁ rmed that, en route to the brain, neurons in the retina 18-2 How do the eye and the brain process and the thalamus code the color-related information from visual information? the cones into pairs of opponent colors.

• After processing by bipolar and ganglion cells in the eyes’ • These two theories, and the research supporting them, retina, neural impulses travel through the optic nerve, to show that color processing occurs in two stages. the thalamus, and on to the visual cortex. In the visual cortex, feature detectors respond to speciﬁ c features of the visual stimulus. Supercell clusters in other critical brain areas respond to more complex patterns. • Through parallel processing, the brain handles many aspects of vision (color, movement, form, and depth) simultaneously. Other neural teams integrate the results, comparing them with stored information and enabling perceptions.

Answers to Multiple-Choice Multiple-Choice Questions 1. 3. Questions Light’s is the distance from one wave peak to Which of the following explains reversed-color

the next. This dimension determines the we afterimages? 1. b 3. c experience. a. Young-Helmholtz trichromatic theory 2. d 4. b a. hue; wavelength b. The blind spot b. wavelength; hue c. Hering’s opponent-process theory c. hue; intensity d. Feature detectors d. wavelength; intensity e. Parallel processing e. intensity; wavelength 4. Your best friend decides to paint her room an extremely 2. What do we call the specialized neurons in the occipital bright electric blue. Which of the following best ﬁ ts the lobe’s visual cortex that respond to particular edges, physical properties of the color’s light waves? lines, angles, and movements? a. No wavelength; large amplitude a. Rods b. Short wavelength; large amplitude b. Cones c. Short wavelength; small amplitude c. Foveas d. Long wavelength; large amplitude d. Feature detectors e. No wavelength; small amplitude e. Ganglion cells

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5. What do we call the transparent, protective layer that 5. c light passes through as it enters the eye? a. Pupil b. Iris c. Cornea d. Lens e. Fovea

Practice FRQs Answer to Practice FRQ 2 1. 2. As light refl ected off an object reaches your eye, it passes Explain two theories of color vision in humans. How 1 point: The Young–Helmholtz through several structures before it reaches the retina. does one of them explain color defi ciency? Describe three of these structures, including the function (3 points) trichromatic theory states that we have of each. 3 color receptors within the eye: red, Answer green, and blue. 1 point: The cornea is at the front of the eye. It bends and focuses the light waves. 1 point: The opponent process theory says that retinal processes only occur in 1 point: The pupil is the opening through which light enters the eyeball. It is surrounded by the iris, which can expand or 3 sets of opponents: red/green, yellow/ contract to allow more or less light to pass through the pupil. blue, and white/black. 1 point: The lens is the transparent structure behind the pupil that changes shape to help focus images on the retina. 1 point: You can explain color defi - ciency as a dysfunction of red- or green-sensitive cones (trichromatic theory) or as a problem with the red– green opponent processes (opponent process theory).

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TEACH TRMTRM Discussion Starter Module 19 Use the Module 19 Fact or Falsehood? student activity from the TRM to intro- Visual Organization and Interpretation duce the concepts from this module.

TEACH Module Learning Objectives

Common Pitfalls 19-119-1 Describe Gestalt psychologists’ understanding of perceptual Students may not understand the organization, and explain how fi gure-ground and grouping principles contribute to our perceptions. Gestalt psychologists’ view that the whole is greater than the sum of its 19-2 Explain how we use binocular and monocular cues to parts. Have them imagine how much perceive the world in three dimensions and perceive motion. the diﬀ erent elements that make 19-3 Explain how perceptual constancies help us organize our sensations up the human body are worth. Even into meaningful perceptions. Rob Kavanagh/Alamy though those elements may be valu- 19-4 Describe what research on restored vision, sensory restriction, and able, their combined value making up perceptual adaptation reveals about the effects of experience on the human body is more valuable than perception. they ever could be on their own.

TEACH Flip It Visual Organization Students can get some additional help 19-119-1 How did the Gestalt psychologists understand perceptual organization, and how do fi gure-ground and grouping principles understanding gestalt by watching contribute to our perceptions? the Flip It Video: Gestalt Psychology on It’s one thing to understand how we see shapes and colors. But how do we organize and this topic. interpret those sights (or sounds or tastes or smells) so that they become meaningful perceptions—a rose in bloom, a familiar face, a sunset? Early in the twentieth century, a group of German psychologists noticed that when gestalt an organized whole. given a cluster of sensations, people tend to organize them into a gestalt, a German word Gestalt psychologists emphasized meaning a “form” or a “whole.” For example, look at FIGURE 19.1. Note that the indi- our tendency to integrate pieces of vidual elements of this ﬁ gure, called a Necker cube, are really nothing but eight blue circles, information into meaningful wholes. each containing three converging white lines. When we view these elements all together, however, we see a cube that sometimes reverses direction. This phenomenon nicely illustrates a favorite saying of Gestalt psychologists: In perception, the whole may exceed the AP® Exam Tip sum of its parts. If we combine sodium (a corrosive metal) with chlorine (a poisonous gas), The Necker cube is an excellent something very different emerges—table salt. Likewise, a unique perceived form emerges vehicle for understanding the from a stimulus’ components (Rock & Palmer, 1990). distinction between sensation Over the years, the Gestalt psychologists demonstrated many principles we use to or- and perception. The only visual stimuli are the blue wedges. The ganize our sensations into perceptions. Underlying all of them is a fundamental truth: Our circles, lines, and cube are all the brain does more than register information about the world. Perception is not just opening a products of perception—they are shutter and letting a picture print itself on the brain. We ﬁ lter incoming information and in your mind and not on the page. construct perceptions. Mind matters.

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Figure 19.1 TEACH A Necker cube What do you see: circles with white lines, or a cube? If you Teaching Tip stare at the cube, you may notice that it reverses location, moving the tiny X in the Have students create their own tessel- center from the front edge to the back. At times, the cube may seem to float in lations like the one in Figure 19.2. This front of the page, with circles behind it. At other times, the circles may become picture is similar to tessellations cre- holes in the page through which the cube appears, as though it were floating ated by M. C. Escher, whose drawings behind the page. There is far more to perception than meets the eye. (From capitalized on fi gure–ground illusions Bradley et al., 1976.) to create fanciful, yet impossible, pictures. A tessellation is a repeating Figure 19.2 geometric pattern, and the ones in Form Perception Reversible figure and ground Figure 19.2 and those that Escher Imagine designing a video-computer system that, like your eye-brain system, can recognize faces at a glance. What abilities would it need? created would combine tessellations with fi gure–ground illusions where FIGURE AND GROUND To start with, the video-computer system would need to separate faces from their backgrounds. 2 geometric patterns would repeat at Likewise, in our eye-brain system, our fi rst perceptual task is to perceive any object (the fi gure) the same time: 1 as a fi gure and 1 as as distinct from its surroundings (the ground). Among the voices you hear at a party, the one a ground. you attend to becomes the fi gure; all others are part of the ground. As you read, the words are the fi gure; the white paper is the ground. Sometimes the same stimulus can trigger more than one perception. In FIGURE 19.2, the fi gure- ground relationship continually reverses—but fi gure- ground the organization ENGAGE always we organize the stimulus into a fi gure seen against a ground. of the visual fi eld into objects (the fi gures) that stand out from their Active Learning GROUPING surroundings (the ground). Having discriminated fi gure from ground, we (and our video-computer system) must also orga- grouping the perceptual tendency Students can discover auditory fi gure– nize the fi gure into a meaningful form. Some basic features of a scene—such as color, movement, to organize stimuli into coherent groups. ground illusions by simply repeating and light-dark contrast—we process instantly and automatically (Treisman, 1987). Our minds bring order and form to stimuli by following certain rules for grouping. These rules, identifi ed by aloud a word such as say. It will shift the Gestalt psychologists and applied even by infants, illustrate how the perceived whole differs abruptly to ace and back again to say. from the sum of its parts (Quinn et al., 2002; Rock & Palmer, 1990). Three examples: PROXIMITY We group nearby fi gures together. We see not six separate lines, but three sets of TEACH two lines.

CONTINUITY We perceive smooth, continuous patterns rather than discontinuous ones. This Common Pitfalls pattern could be a series of alternating semicircles, but we perceive it as two continuous Students typically fi nd gestalt group- lines—one wavy, one straight. ing principles to be very mundane and CLOSURE We fi ll in gaps to create a complete, whole object. Thus we assume that the circles obvious. Remind students that the on the right are complete but partially blocked by the (illusory) triangle. Add nothing more than little line segments to close off the circles and your brain stops constructing a triangle. Gestalt psychologists were the fi rst to Such principles usually help us construct reality. study systematically how people perceive whole objects. Before their work, people took these grouping principles for granted.

Proximity Continuity Closure

MyersAP_SE_2e_Mod19_B.indd 182 1/21/14 9:33 AM MyersAP_SE_2e_Mod19_B.indd TEACH 183 1/21/14 9:33 AM Teaching Tip Use the following examples of 2 of the gestalt Similarity: Items that look the same are grouping principles to help students remem- usually grouped together. Have students ber them: imagine their reactions when someone Proximity: We perceive items that are they do not know well wears the same close to each other as being together. Have outfit or shirt as they do. Typically, they are students imagine their reactions when uncomfortable with this because we do not someone they do not know well walks in like being grouped with people we do not step with them down the hall. Typically, know well. people feel discomfort when this happens because of their proximity to the other person. We do not like to be grouped together with people we do not know well.

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TEACH Depth Perception 19-219-2 How do we use binocular and monocular cues to perceive the world Concept Connections in three dimensions and perceive motion? Refer students to Unit IX for a thorough From the two- dimensional images falling on our retinas, we somehow organize three-di-

discussion of infant development. mensional perceptions. Depth perception enables us to estimate an object’s distance from us. At a glance, we can estimate the distance of an oncoming car or the height of a house. The visual cliff study, a classic in the Depth perception is partly innate, as Eleanor Gibson and Richard Walk (1960) discovered fi eld, helped demonstrate how infants using a model of a cliff with a drop- off area (which was covered by sturdy glass). Gibson’s inspiration for these visual cliff experiments occurred while she was picnicking on the rim perceive depth and ways to measure of the Grand Canyon. She wondered: Would a toddler peering over the rim perceive the infant perceptions without relying on dangerous drop - off and draw back? language. Back in their Cornell University lab- Figure 19.3 oratory, Gibson and Walk placed 6- to Visual cliff Eleanor Gibson and 14-month- old infants on the edge of a safe ENGAGE Richard Walk devised a miniature canyon and had the infants’ mothers coax cliff with a glass- covered drop -off to determine whether crawling infants them to crawl out onto the glass (FIGURE TRMTRM Enrichment can perceive depth. Even when 19.3). Most infants refused to do so, indicat- coaxed, infants are reluctant to ing that they could perceive depth. We are able to perceive depth because venture onto the glass over the cliff (Gibson & Walk, 1960). Had they learned to perceive depth? we have 2 eyes in the front of our Learning seems to be part of the answer heads. Animals with eyes on the because crawling, no matter when it be- sides of their heads need that type gins, seems to increase infants’ wariness of heights (Campos et al., 1992). Yet, the re- of vision to scan for danger around searchers observed, mobile newborn ani- them. Peripheral vision is much bet- mals come prepared to perceive depth. Even those with virtually no visual experience— ter at detecting motion, so stronger including young kittens, a day-old goat, and newly hatched chicks—will not venture across peripheral vision through eyes on the the visual cliff. Thus, it seems that biology predisposes us to be wary of heights and experi- sides of the head gives an evolutionary ence amplifi es that fear. How do we perceive depth? How do we transform two differing two - dimensional (2-D) advantage to animals that are typically retinal images into a single three - dimensional (3-D) perception? Our brain constructs these hunted. Predators do not need to be perceptions using information supplied by one or both eyes.

on the look out for danger—they are depth perception the ability BINOCULAR CUES the danger! They need to determine to see objects in three dimensions Try this: With both eyes open, hold two pens or pencils in front of you and touch their although the images that strike the distances between them and their retina are two - dimensional; allows tips together. Now do so with one eye closed. With one eye, the task becomes noticeably binocular cues prey, which requires the depth percep- us to judge distance. more diffi cult, demonstrating the importance of in judging the distance of nearby objects. Two eyes are better than one. visual cliff a laboratory device for tion that binocular vision provides. testing depth perception in infants Because your eyes are about 2½ inches apart, your retinas receive slightly different im- Use Student Activity: Binocular Vision and young animals. ages of the world. By comparing these two images, your brain can judge how close an object is to you. The greater the retinal disparity, or difference between the two images, the closer Versus Monocular Vision from the binocular cues depth cues, such as retinal disparity, that depend on the object. Try it. Hold your two index fi ngers, with the tips about half an inch apart, directly TRM to demonstrate the value of the use of two eyes. in front of your nose, and your retinas will receive quite different views. If you close one eye binocular cues. retinal disparity a binocular cue and then the other, you can see the difference. (You may also create a fi nger sausage, as in for perceiving depth: By comparing FIGURE 19.4.) At a greater distance—say, when you hold your fi ngers at arm’s length—the images from the retinas in the two disparity is smaller. eyes, the brain computes distance— We could easily build this feature into our video-computer system. Moviemakers the greater the disparity (difference) between the two images, the closer can simulate or exaggerate retinal disparity by fi lming a scene with two cameras placed the object. a few inches apart. Viewers then wear glasses that allow the left eye to see only the image from the left camera, and the right eye to see only the image from the right camera.

MyersAP_SE_2e_Mod19_B.inddTEACH 184 TEACH 1/21/14 9:33 AM MyersAP_SE_2e_Mod19_B.indd 185 1/21/14 9:33 AM Teaching Tip Online Activities Relate retinal disparity to real life by having Some people cannot see depth well because of students recall a time when they were lying diﬀ erent conditions that hinder the eyes’ ability down watching television. Ask them if they to see in stereo. Check out www.vision3d.com ever had their vision in one eye obscured by to ﬁ nd the answers to the following questions: a pillow or blanket they were lying with. If so, What is amblyopia (lazy eye)? What are then they probably had to shift their position some treatments for this condition? to correct the obstruction or close one eye: What is strabismus (deflected eye, crossed watching TV and a pillow at the same time is eyes, or wall eyes)? What are some not very enjoyable! treatments for this condition? How are vision problems related to learning disabilities and dyslexia?

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FYI ENGAGE Carnivorous animals, including humans, have eyes that enable TRMTRM forward focus on a prey and offer Active Learning binocular vision-enhanced depth perception. Grazing herbivores, Try to round up some Viewmasters such as horses and sheep, typically to demonstrate retinal disparity in have eyes on the sides of their skull. Although lacking binocular class. Students can view the images depth perception, they have sweeping peripheral vision. with 1 eye closed and both eyes open to see how the same image is pro- Figure 19.4 The floating finger sausage Hold jected in 2 slightly diﬀ erent places to your two index fingers about 5 inches in front of your eyes, with their tips half an capitalize on our perception of depth. inch apart. Now look beyond them and Use Student Activity: Autostereograms note the weird result. Move your fingers out farther and the retinal disparity—and from the TRM to demonstrate depth the finger sausage—will shrink. perception using a Magic Eye™-like

The resulting 3-D effect, as 3-D movie fans know, mimics or exaggerates normal retinal activity. disparity. Similarly, twin cameras in airplanes can take photos of terrain for integration into 3-D maps. ENGAGE MONOCULAR CUES Active Learning How do we judge whether a person is 10 or 100 meters away? Retinal disparity won’t help us here, because there won’t be much difference between the images cast on our right and Have students roll a sheet of paper into monocular cues depth cues, left retinas. At such distances, we depend on monocular cues (depth cues available to a tube and raise it to their right eye like each eye separately). See FIGURE 19.5 on the next page for some examples. such as interposition and linear perspective, available to either eye a telescope. Tell them to look through alone. Motion Perception it, focusing on a blank wall in front phi phenomenon an illusion of Imagine that you could perceive the world as having color, form, and depth but that you movement created when two or of them. Next, have them hold their could not see motion. Not only would you be unable to bike or drive, you would have more adjacent lights blink on and trouble writing, eating, and walking. off in quick succession. left hand open beside the tube and Normally your brain computes motion based partly on its assumption that shrinking continue to focus ahead. The images objects are retreating (not getting smaller) and enlarging objects are approaching. But you received by the 2 eyes will fuse, and are imperfect at motion perception. Large objects, such as trains, appear to move more slowly than smaller objects, such as cars, moving at the same speed. (Perhaps at an airport the hole in the tube will appear to be you’ve noticed that jumbo jets seem to land more slowly than little jets.) in the student’s hand. They may need To catch a fl y ball, softball or cricket players (unlike drivers) want to achieve a collision— to slide the hand alongside the tube with the ball that’s fl ying their way. To accomplish that, they follow an unconscious rule— one they can’t explain but know intuitively: Run to keep the ball at a constantly increasing until they fi nd the precise spot where “Sometimes I wonder: Why is that angle of gaze (McBeath et al., 1995). A dog catching a Frisbee does the same (Shaffer et al., Frisbee getting bigger? And then the hole appears to go through the 2004). it hits me.” -ANONYMOUS The brain also perceives continuous movement in a rapid series of slightly varying im- very center of the palm. ages (a phenomenon called stroboscopic movement). As fi lm animation artists know well, Fisher, J. (1979). Body magic. New York: Stein you can create this illusion by fl ashing 24 still pictures a second. The motion we then see in popular action adventures is not in the fi lm, which merely presents a superfast slide show. and Day. We construct that motion in our heads, just as we construct movement in blinking marquees “From there to here, from and holiday lights. When two adjacent stationary lights blink on and off in quick succession, here to there, funny things are we perceive a single light moving back and forth between them. Lighted signs exploit this everywhere.” -DR. SEUSS, ONE FISH, ENGAGE phi phenomenon with a succession of lights that creates the impression of, say, a moving TWO FISH, RED FISH, BLUE FISH, 1960 arrow. Online Activities In a computer lab or as a homework assignment, have students try out some of the 3D vision games found in the Optometrists Network at MyersAP_SE_2e_Mod19_B.indd 184 1/21/14 9:33 AM MyersAP_SE_2e_Mod19_B.inddENGAGE 185 ENGAGE 1/21/14 9:33 AM www.vision3d.com. Eye Hop Game: www.vision3d.com/ Active Learning Enrichment ehop.html Have students close 1 eye, point their 2 forefi n- Although we can see depth with only 1 eye, it Framing Game: www.vision3d.com/ gers toward each other, and then bring them is much more diffi cult to perceive depth with frame.html together quickly. They are likely to miss. An 1 eye closed than with both eyes open. Reversible figures: www.vision3d. even more diffi cult test is to have them hold Animals with eyes on the sides of their heads com/optical/puzzles.html a pencil in each hand and bring the points (birds, rabbits, etc.) tend to compensate for together. It is important, of course, that their their lack of depth perception by moving their hands not be at arm’s length. If they repeat heads around a lot to as they try to look around either test, they ought to drop their arms out of objects. This type of movement, which creates view before they try again. This will eliminate depth, is called monocular parallax. the perception of any depth cues from the position of the hands and arms.

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TEACH Common Pitfalls Students may feel that the monocular © Philip Mugridge/Alamy depth cues are more common sense than psychology. Emphasize that without these cues, many forms of enter- et al., 2002 stimuli that appeared in Vecrera tainment—from art to television to Ph.D., adapted from Vecera, Image courtesy Shaun P. Relative height We perceive objects movies—would lack the visual richness higher in our field of vision as farther away. Because we assume the lower part and beauty they possess. Monocular of a figure-ground illustration is closer, we perceive it as figure (Vecera et al., 2002). depth cues help make the world a Invert this illustration and the black will Interposition Interpose means “to come Relative size If we assume two become ground, like a night sky. between.” If one object partially blocks our view more visually interesting place! objects are similar in size, most people of another, we perceive it as closer. perceive the one that casts the smaller retinal image as farther away. Relative motion As we move, objects TEACH that are actually stable may appear to move. If while riding on a bus you fix your gaze on some point—say, a house—the objects Flip It beyond the fixation point will appear to move with you. Objects in front of the point will Students can get some additional appear to move backward. The farther an object is from the fixation point, the faster it will help understanding monocular Linear perspective Parallel lines appear to meet in seem to move. the distance. The sharper the angle of convergence, the Shading cues by watching the Flip It Video: greater the perceived distance. Light and shadow produces a sense of depth Monocular Cues. consistent with our assumption Fixation that light comes from above. If you point invert this illustration, the hollow will TEACH become a hill.

Teaching Tip Reserved.

Many of these monocular depth cues cartoonbank.com. All Rights Reserved. rely on previous knowledge in order to work. If we don’t already know how Collection, 2002, Jack Ziegler from ©The New Yorker Vilayanur S. Ramachandran. Copyright © From “Perceiving Shape Shading” by 1988 by Scientiﬁ c American, Inc. All Rights 1988 by Scientiﬁ large an object is, then the relative Direction of passenger’s motion size cue becomes meaningless. Here Figure 19.5 is where top-down processing is most Monocular depth cues useful in helping us accurately under- Perceptual Constancy

stand the world. Have students explain AP® Exam Tip 19-3 How do perceptual constancies help us organize our sensations into meaningful perceptions? how top-down processing is useful. The illustrations in Figure 19.5 provide you with excellent So far, we have noted that our video-computer system must perceive objects as we do—as opportunities to practice identifying monocular depth having a distinct form, location, and perhaps motion. Its next task is to recognize objects TEACH cues. To really demonstrate your without being deceived by changes in their color, brightness, shape, or size—a top-down understanding, look for these process called perceptual constancy. Regardless of the viewing angle, distance, and il- Teaching Tip cues in other drawings and lumination, we can identify people and things in less time than it takes to draw a breath, photographs. There are almost Divide students into small groups always cues to identify. a feat that would be a monumental challenge for even advanced computers and that has intrigued researchers for decades. and have them compile a portfolio of examples of monocular depth cues. Have them bring in their own maga- zines (or collect back issues from your library) to look for examples of each type of monocular cue, collecting ENGAGEMyersAP_SE_2e_Mod19_B.indd 186 TEACH 1/21/14 9:33 AM MyersAP_SE_2e_Mod19_B.indd 187 1/21/14 9:33 AM them in a scrapbook or poster and identifying the one that each picture Active Learning Teaching Tip exemplifi es. Boston’s Museum of Science off ers a wonderful Another monocular cue students should know online lesson in which students can create a is texture gradient. This is the tendency for realistic and natural picture using linear per- textured surfaces to appear to become smaller spective. The Leonardo’s Window lesson asks and fi ner as distance from the viewer increases. students to tape some acetate onto a window For example, a hiker in a fi eld of fl owers will and trace the lines found in the natural world see the closest fl owers clearly, but the details outside to create a painting. For more instruc- of the fl owers become less apparent and seem tions, see http://legacy.mos.org/sln/Leonardo/ smaller the farther into the distance he looks. UsingLeosWindow.html.

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COLOR AND BRIGHTNESS CONSTANCIES perceptual constancy perceiving ENGAGE Color does not reside in an object. Our experience of color depends on the object’s context. objects as unchanging (having If you view an isolated tomato through a paper tube, its color would seem to change as the consistent shapes, size, brightness, Active Learning light—and thus the wavelengths refl ected from its surface—changed. But if you viewed and color) even as illumination and that tomato as one item in a bowl of fresh fruit and vegetables, its color would remain retinal images change. Bring in 2 sets of men’s dress socks roughly constant as the lighting shifts. This perception of consistent color is known as color constancy perceiving (one dark blue and one black). In dim color constancy. familiar objects as having consistent Though we take color constancy for granted, this ability is truly remarkable. A blue color, even if changing illumination light, have students identify the color poker chip under indoor lighting refl ects wavelengths that match those refl ected by a alters the wavelengths refl ected by the object. of the socks. Do the same in brighter sunlit gold chip (Jameson, 1985). Yet bring a bluebird indoors and it won’t look like a goldfi nch. The color is not in the bird’s feathers. You and I see color thanks to our brain’s light. Although the task may be easier computations of the light refl ected by an object relative to the objects surrounding it. (But in brighter light, it is still not defi nitive only if we grew up with normal light, it seems. Monkeys raised under a restricted range until both colors of socks are compared of wavelengths later have great diffi culty recognizing the same color when illumination varies [Sugita, 2004].) FIGURE 19.6 dramatically illustrates the ability of a blue object to to each other. Sometimes blue and appear very different in three different contexts. Yet we have no trouble seeing these disks black are diffi cult to distinguish in dim as blue. light, which is why getting dressed in the dark can often bring about mis- Figure 19.6 matches when choosing dark socks or Color depends on context (a) Believe it or not, these three blue shoes to wear! disks are identical in color. (b) Remove the surrounding context and see what results. TEACH

R. Beau Lotto at University College, London Teaching Tip Cite an interesting example of depth cues working to create an illusion of reality by discussing the proportions of Michelangelo’s sculpture, The Pieta. The Pieta depicts the Virgin Mary hold- (a) (b) ing her dead son Jesus. Although the fi gure of Christ is lifelike and propor- Similarly, brightness constancy (also called lightness constancy) depends on context. We perceive an object as having a constant brightness even while its illumination varies. This tional to reality, if the fi gure of Mary perception of constancy depends on relative luminance—the amount of light an object re- were to rise to her feet and stand erect, fl ects relative to its surroundings (FIGURE 19.7 on the next page). White paper refl ects 90 she would be over 7’ tall! But to look at percent of the light falling on it; black paper, only 10 percent. Although a black paper viewed in sunlight may refl ect 100 times more light than does a white paper viewed indoors, it will the sculpture, one would never notice still look black (McBurney & Collings, 1984). But if you view sunlit black paper through a Mary was so much larger than her son narrow tube so nothing else is visible, it may look gray, because in bright sunshine it refl ects a fair amount of light. View it without the tube and it is again black, because it refl ects much in reality. less light than the objects around it. This principle—that we perceive objects not in isolation but in their environmental context—matters to artists, interior decorators, and clothing designers. Our perception of the color and brightness of a wall or of a streak of paint on a canvas is determined not just by the paint in the can but by the surrounding colors. The take- home lesson: Comparisons govern our perceptions.

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TEACH Figure 19.7 Relative luminance Squares A Teaching Tip and B are identical in color, believe it or not. (If you don’t believe me, Have students imagine how disturb- photocopy the illustration, cut out the squares, and compare.) But we ing the world would be if we suddenly perceive A as lighter, thanks to its lost our ability to perceive constancy. surrounding context. What if objects appeared to change shape when they moved? What if color A became diﬀ erent in diﬀ erent levels of light? “My monster little brother” would take on a whole new meaning if he grew and changed shapes and B colors right before your eyes!

ENGAGE Active Learning The importance of perceptual constancy is demonstrated in the follow- SHAPE AND SIZE CONSTANCIES ing passage: Sometimes an object whose actual shape cannot change seems to change shape with the angle of our view (FIGURE 19.8). More often, thanks to shape constancy, we perceive the I cdnuolt blveiee taht I cluod aulaclty form of familiar objects, such as the door in FIGURE 19.9, as constant even while our reti- uesdnatnrd waht I was rdanieg. Takhns nas receive changing images of them. Our brain manages this feat thanks to visual cortex neurons that rapidly learn to associate different views of an object (Li & DiCarlo, 2008). to the phaonmneal pweor of the Thanks to size constancy, we perceive objects as having a constant size, even while our hmuan mnid, aoccdrnig to rscheearch distance from them varies. We assume a car is large enough to carry people, even when we at Cmabrigde Uinervtisy, it deosn’t see its tiny image from two blocks away. This assumption also illustrates the close connec- mttaer in waht oredr the ltteers in a tion between perceived distance and perceived size. Perceiving an object’s distance gives us cues to its size. Likewise, knowing its general size—that the object is a car—provides us wrod are, the olny iprmoatnt tihng is with cues to its distance. taht the frist and lsat ltteer be in the rghit pclae. The rset can be a taotl mses and you can sitll raed it wouthit a porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Amzanig, huh? Yaeh and I awlyas tghuhot slpeling was ipmorantt! if you can raed tihs, psas it on!!

While this popular Internet message Figure 19.8 Perceiving shape Do the tops of these Figure 19.9 was not really based on a study by tables have different dimensions? They appear Shape constancy A door casts an Cambridge University, and its scientiﬁ c to. But—believe it or not—they are identical. increasingly trapezoidal image on our (Measure and see.) With both tables, we adjust retinas as it opens, yet we still perceive it validity is in serious doubt, the fact that our perceptions relative to our viewing angle. as rectangular. people can still decipher this para- graph is testimony to the power of the brain to make sense out of nonsense. Have students discuss ways to test the MyersAP_SE_2e_Mod19_B.indd 188 1/21/14 9:33 AM MyersAP_SE_2e_Mod19_B.indd 189 1/21/14 9:33 AM claims of this passage scientiﬁ cally.

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Even in size-distance judgments, however, we consider an object’s context. The dogs in Module 17’s Figure 17.3 cast identical images on our retinas. Using linear perspective as a ENGAGE cue (see Figure 19.5), our brain assumes that the pursuing dog is farther away. We therefore perceive it as larger. It isn’t. TRMTRM Enrichment This interplay between perceived size and perceived distance helps explain several When Spanish conquistadors explored well -known illusions, including the Moon illusion: The Moon looks up to 50 percent larger when near the horizon than when high in the sky. Can you imagine why? For at least 22 the southwestern United States, their centuries, scholars have debated this question (Hershenson, 1989). One reason is that perception was tricked as they looked cues to objects’ distances make the horizon Moon—like the distant dog in Figure 17.3— down on the Colorado River from the appear farther away. If it’s farther away, our brain assumes, it must be larger than the Moon high in the night sky (Kaufman & Kaufman, 2000). Take away the distance cue, by rim of the Grand Canyon. What they looking at the horizon Moon (or each dog) through a paper tube, and the object will im- perceived to be a small running creek mediately shrink. about 6’ wide was actually a raging Size - distance relationships also explain why in FIGURE 19.10 the two same-age girls seem so different in size. As the diagram reveals, the girls are actually about the same size, river over a mile wide! The perceptual but the room is distorted. Viewed with one eye through a peephole, the room’s trapezoidal cues from the top of the canyon fooled walls produce the same images you would see in a normal rectangular room viewed with both eyes. Presented with the camera’s one- eyed view, your brain makes the reasonable them into thinking the river was much assumption that the room is normal and each girl is therefore the same distance from you. smaller than it really was. Use Student Given the different sizes of the girls’ images on your retinas, your brain ends up calculating Activity: Perceived Lunar Size from the that the girls must be very different in size. Perceptual illusions reinforce a fundamental lesson: Perception is not merely a projec- TRM to demonstrate this phenomenon. tion of the world onto our brain. Rather, our sensations are disassembled into information bits that our brain, using both bottom-up and top-down processing, then reassembles into its own functional model of the external world. During this reassembly process, our as- ENGAGE sumptions—such as the usual relationship between distance and size—can lead us astray. Our brain constructs our perceptions. Active Learning * * * Have students hold a hand in front of Form perception, depth perception, motion perception, and perceptual constancies illumi- their face at arm’s length and move nate how we organize our visual experiences. Perceptual organization applies to our other Figure 19.10 senses, too. It explains why we perceive a clock’s steady tick not as a tick-tick-tick-tick but it toward their head, then away; they The illusion of the shrinking as grouped sounds, say, TICK-tick, TICK-tick. Listening to an unfamiliar language, we have and growing girls This will perceive no change in size. The trouble hearing where one word stops and the next one begins. Listening to our own lan- distorted room, designed by guage, we automatically hear distinct words. This, too, refl ects perceptual organization. But Adelbert Ames, appears to have size of the retinal image is, of course, a normal rectangular shape when it is more, for we even organize a string of letters—THEDOGATEMEAT—into words that viewed through a peephole with changing. Now, have students hold make an intelligible phrase, more likely “The dog ate meat” than “The do gate me at” one eye. The girl in the right corner the forefi nger of their left hand about (McBurney & Collings, 1984). This process involves not only the organization we’ve been appears disproportionately large because we judge her size based 8" in front of their face and focus on discussing, but also interpretation—discerning meaning in what we perceive. on the false assumption that she is the same distance away as the girl it. They should then position their in the left corner. right hand at arm’s length, past their left forefi nger. While maintaining fi xation on their left fi ngertip, they should move their right hand toward and away from their face. Although

S. Schwartzenberg/The Exploratorium their focus should be on the ﬁ nger, they should also notice the image of the hand as it moves. It will change dramatically in size.

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Visual Interpretation Philosophers have debated whether our perceptual abilities should be credited to our nature or our nurture. To what extent do we learn to perceive? German philosopher Immanuel Kant “Let us then suppose the mind to (1724–1804) maintained that knowledge comes from our inborn ways of organizing sensory be, as we say, white paper void of experiences. Indeed, we come equipped to process sensory information. But British philoso- all characters, without any ideas: How comes it to be furnished? pher John Locke (1632–1704) argued that through our experiences we also learn to perceive . . . To this I answer, in one word, the world. Indeed, we learn to link an object’s distance with its size. So, just how important from EXPERIENCE.” -JOHN LOCKE, is experience? How radically does it shape our perceptual interpretations? AN ESSAY CONCERNING HUMAN UNDERSTANDING, 1690 Experience and Visual Perception

19-419-4 What does research on restored vision, sensory restriction, and perceptual adaptation reveal about the effects of experience on perception?

RESTORED VISION AND SENSORY RESTRICTION TEACH Writing to John Locke, William Molyneux wondered whether “a man born blind, and now adult, taught by his touch to distinguish between a cube and a sphere” could, if made to see, Concept Connections visually distinguish the two. Locke’s answer was No, because the man would never have Critical periods are discussed here as learned to see the difference. Molyneux’s hypothetical case has since been put to the test with a few dozen adults well as in Units VII and IX. Be sure to who, though blind from birth, have gained sight (Gregory, 1978; von Senden, 1932). Most help students connect this discussion had been born with cataracts—clouded lenses that allowed them to see only diffused light, rather as someone might see a foggy image through a Ping - Pong ball sliced in half. After with the later ones. Learning to see: At age 3, Mike cataract surgery, the patients could distinguish fi gure from ground and could sense colors— May lost his vision in an explosion. suggesting that these aspects of perception are innate. But much as Locke supposed, they Decades later, after a new cornea often could not visually recognize objects that were familiar by touch. ENGAGE restored vision to his right eye, he got his first look at his wife and children. Seeking to gain more control than is provided by clinical cases, researchers have outfi t- TRMTRM Enrichment Alas, although signals were now ted infant kittens and monkeys with goggles through which they could see only diffuse, un- reaching his visual cortex, it lacked patterned light (Wiesel, 1982). After infancy, when the goggles were removed, these animals the experience to interpret them. May Myers describes experiments in which could not recognize expressions, or exhibited perceptual limitations much like those of humans born with cataracts. They could infant animals were outfi tted with faces, apart from features such as hair. distinguish color and brightness, but not the form of a circle from that of a square. Their Yet he can see an object in motion eyes had not degenerated; their retinas still relayed signals to their visual cortex. But lack- goggles through which they could and has learned to navigate his world and to marvel at such things as dust ing stimulation, the cortical cells had not developed normal connections. Thus, the animals only see diff use, unpatterned light. floating in sunlight (Abrams, 2002). remained functionally blind to shape. Experience guides, sustains, and maintains the brain’s Use of this type of apparatus is called neural organization as it forms the pathways that affect our perceptions. In both humans and animals, similar sensory restrictions later in life do no a Ganzfeld procedure. This procedure permanent harm. When researchers cover the eye of an adult animal for several is often used to create an experience months, its vision will be unaffected after the eye patch is removed. When surgeons remove cataracts that develop during late adulthood, most people are thrilled at of sensory deprivation. Use Student the return to normal vision. Activity: The Ganzfeld from the TRM to The effect of sensory restriction on infant cats, monkeys, and humans sug- demonstrate how the elimination of gests there is a critical period for normal sensory and perceptual development. Nurture sculpts what nature has endowed. In less dramatic ways, it continues to contours eff ectively eliminates visual do so throughout our lives. Despite concerns about their social costs (more on perception. this in Module 78), action video games sharpen spatial skills such as visual attention, eye-hand coordination and speed, and tracking multiple objects (Spence & Feng, 2010). Experiments on early sensory deprivation provide a partial answer to the enduring question about experience: Does the effect of early experience last a life- time? For some aspects of perception, the answer is clearly Yes: “Use it soon or lose

AP Photo/Marcio Jose Sanchez it.” We retain the imprint of some early sensory experiences far into the future.

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PERCEPTUAL ADAPTATION ENGAGE Given a new pair of glasses, we may feel slightly disoriented, even dizzy. Within a day or two, we adjust. Our perceptual adaptation to changed visual input makes the world seem TRMTRM Active Learning normal again. But imagine a far more dramatic new pair of glasses—one that shifts the apparent location of objects 40 degrees to the left. When you fi rst put them on and toss a ball perceptual adaptation in Create or purchase visual distortion vision, the ability to adjust to to a friend, it sails off to the left. Walking forward to shake hands with the person, you veer an artifi cially displaced or even goggles for students to use in class. to the left. inverted visual fi eld. Could you adapt to this distorted world? Baby chicks cannot. When fi tted with such (You can purchase goggles from lenses, they continue to peck where food grains seem to be (Hess, 1956; Rossi, 1968). But we www.psychkits.com). Have students humans adapt to distorting lenses quickly. Within a few minutes your throws would again be accurate, your stride on target. Remove the lenses and you would experi- toss soft balls to each other as they ence an aftereffect: At fi rst your throws would err in the opposite direction, sailing off wear the goggles. After a few tries, they to the right; but again, within minutes you would readapt. will fi nd they can throw accurately. Indeed, given an even more radical pair of glasses—one that literally turns the

world upside down—you could still adapt. Psychologist George Stratton (1896) ex- Courtesy of Hubert Dolezal Then have them take off the goggles. perienced this when he invented, and for eight days wore, optical headgear that They will need a few more tries to fl ipped left to right and up to down, making him the fi rst person to experience a throw accurately again because their right - side- up retinal image while standing upright. The ground was up, the sky was down. vision will be distorted in the opposite At fi rst, when Stratton wanted to walk, he found himself searching for his feet, way from what it was while they were which were now “up.” Eating was nearly impossible. He became nauseated and depressed. But he persisted, and by the eighth day he could comfortably reach for an wearing the goggles. Use Student object in the right direction and walk without bumping into things. When Stratton Activity: Displacement Goggles from fi nally removed the headgear, he readapted quickly. the TRM for a tutorial on how to create In later experiments, people wearing the optical gear have even been able to ride a motorcycle, ski the Alps, and fl y an airplane (Dolezal, 1982; Kohler, 1962). displacement goggles. The world around them still seemed above their heads or on the wrong side. But by actively moving about in these topsy - turvy worlds, they adapted to the context and CLOSE & ASSESS learned to coordinate their movements. Perceptual adaptation “Oops, missed,” thought researcher Hubert Dolezal as he viewed the world through Exit Assessment inverting goggles. Yet, believe it or not, kittens, monkeys, and humans can Many of the concepts in this module Before You Move On adapt to an inverted world. are confusing or unfamiliar to stu- ᭤ ASK YOURSELF dents. Choose 2–4 concepts and have Try drawing a realistic depiction of the scene from your window. Which monocular cues will you use in your drawing? students write a short explanation of the concept as if they were explaining ᭤ TEST YOURSELF What do we mean when we say that, in perception, “the whole is greater than the sum of its it to an elementary student. This will parts”? help you see if students understand Answers to the Test Yourself questions can be found in Appendix E at the end of the book. the material well enough to explain it simply and concisely.

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Module 19 Review How did the Gestalt psychologists 19-119-1 19-319-3 How do perceptual constancies help us understand perceptual organization, organize our sensations into meaningful and how do fi gure-ground and grouping perceptions? principles contribute to our perceptions? • Perceptual constancy enables us to perceive objects as stable • Gestalt psychologists searched for rules by which the despite the changing image they cast on our retinas. brain organizes fragments of sensory data into gestalts • Color constancy is our ability to perceive consistent color (from the German word for “whole”), or meaningful in objects, even though the lighting and wavelengths forms. In pointing out that the whole may exceed the sum shift. of its parts, they noted that we fi lter sensory information • Brightness (or lightness) constancy is our ability to and construct our perceptions. perceive an object as having a constant lightness even when its illumination—the light cast upon it—changes. To recognize an object, we must fi rst perceive it (see it as • • Our brain constructs our experience of an object’s a fi gure) as distinct from its surroundings (the ground). color or brightness through comparisons with other We bring order and form to stimuli by organizing them surrounding objects. into meaningful groups, following such rules as proximity, • Shape constancy is our ability to perceive familiar continuity, and closure. objects (such as an opening door) as unchanging in shape. 19-219-2 How do we use binocular and monocular cues to perceive the world in three • Size constancy is perceiving objects as unchanging in dimensions and perceive motion? size despite their changing retinal images. • Knowing an object’s size gives us clues to its distance; • Depth perception is our ability to see objects in three knowing its distance gives clues about its size, but we dimensions and judge distance. The visual cliff and other sometimes misread monocular distance cues and reach research demonstrate that many species perceive the the wrong conclusions, as in the Moon illusion. world in three dimensions at, or very soon after, birth. What does research on restored vision, Binocular cues, such as retinal disparity, are depth cues that 19-4 • sensory restriction, and perceptual rely on information from both eyes. adaptation reveal about the effects of • Monocular cues (such as relative size, interposition, relative experience on perception? height, relative motion, linear perspective, and light and shadow) let us judge depth using information transmitted • Experience guides our perceptual interpretations. People by only one eye. blind from birth who gained sight after surgery lack • As objects move, we assume that shrinking objects are the experience to visually recognize shapes, forms, and retreating and enlarging objects are approaching. complete faces. • A quick succession of images on the retina can create an • Sensory restriction research indicates that there is a illusion of movement, as in stroboscopic movement or the critical period for some aspects of sensory and perceptual phi phenomenon. development. Without early stimulation, the brain’s neural organization does not develop normally. • People given glasses that shift the world slightly to the left or right, or even upside down, experience perceptual adaptation. They are initially disoriented, but they manage to adapt to their new context.

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Multiple-Choice Questions Answers to Multiple-Choice 1. A teacher used distortion goggles, which shifted the 3. Bryanna and Charles are in a dancing competition. It is Questions wearer’s gaze 20 degrees, to demonstrate an altered easy for spectators to see them against the dance fl oor perception. A student wearing the goggles initially because of 1. a 3. e 5. a bumped into numerous desks and chairs while walking a. the visual cliff. 2. a 4. a around, but chose to wear the goggles for a half hour. b. the phi phenomenon. After 30 minutes, the student was able to smoothly avoid c. color constancy. obstacles, illustrating the concept of d. sensory restriction. a. perceptual adaptation. e. fi gure-ground relationships. b. visual interpretation. 4. The view from Narmeen’s left eye is slightly different c. sensory restriction. from the view from her right eye. This is due to which d. perceptual constancy. depth cue? e. binocular cues. a. Retinal disparity 2. What do we call the illusion of movement that results b. Relative size from two or more stationary, adjacent lights blinking on c. Linear perspective and off in quick succession? d. Relative motion a. Phi phenomenon e. Convergence b. Perceptual constancy 5. Bringing order and form to stimuli, which illustrates how c. Binocular cues the whole differs from the sum of its parts, is called d. Retinal disparity e. Depth perception a. grouping. b. monocular cue. c. binocular cue. d. disparity. e. motion. Practice FRQs Answer to Practice FRQ 2 1. Look at the relative size cartoon in Figure 19.5. Describe 2. Explain the meaning of the word gestalt as it applies to 1 point: A gestalt is a unifi ed whole. how the artist who drew this cartoon incorporated perception. Then, apply any two gestalt principles to the relative size, linear perspective, and interposition to perception of food on a plate. We perceive the world in unifi ed create depth. (3 points) groups or patterns. Answer 1 point: Student must apply 2 gestalt Specifi c explanations may utilize different aspects of the cartoon. principles to the perception of food on 1 point: Relative size: We know the woman is closer to us than the police offi cer, because she is drawn larger. a plate. Examples might include: 1 point: Linear perspective: We can tell that the sidewalk Figure–ground: The food is the is receding into the distance, because its sides pinch closer figure that stands out against the together in the distance. ground of the plate. 1 point: Interposition: We know the woman is closer to us than the police offi cer, because our view of her partially Similarity: A dozen Tater Tots would blocks our view of him. be perceived as a group because the tots all look pretty much alike. Proximity: Green peas would be perceived as a group because they would be near one another on the plate.

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TEACH TRMTRM Discussion Starter Module 20 Use the Module 20 Fact or Falsehood student activity from the TRM to intro- Hearing duce the concepts from this module.

ENGAGE Module Learning Objectives

Active Learning 20-120-1 Describe the characteristics of air pressure waves, and explain the process by which the ear transforms sound Have band students bring in their Leland Bobbé/CORBIS energy into neural messages. instruments to demonstrate how vibrations work with the diﬀ erent 20-220-2 Discuss the theories that help us understand pitch perception.

instruments. 20-320-3 Describe how we locate sounds. What produces the vibrations in each instrument? How does the instrument produce louder and softer sounds? 20-1 What are the characteristics of air pressure waves that we hear as sound, and how does the ear transform sound energy into neural messages? Like our other senses, our audition, or hearing, is highly adaptive. We hear a wide range of sounds, but the ones we hear best are those sounds with frequencies in a range corresponding to that of the human voice. Those with normal hearing are acutely sensitive to audition the sense or act of faint sounds, an obvious boon for our ancestors’ survival when hunting or being hunted, hearing. or for detecting a child’s whimper. (If our ears were much more sensitive, we would hear a constant hiss from the movement of air molecules.) We are also remarkably attuned to variations in sounds. We easily detect differences among thousands of possible human voices: Walking between classes, we immediately recognize the voice of a friend behind us. A fraction of a second after a spoken word ® AP Exam Tip stimulates the ear’s receptors, millions of neurons have simultaneously coordinated in Pay attention to how many extracting the essential features, comparing them with past experience, and identifying pages are devoted to each the stimulus (Freeman, 1991). of the senses. Not only does But not everyone has this ability. Some years ago, on a visit to my childhood home, I this represent the complexity of the sensory system, it also communicated with my then 80-year-old mother by writing on her erasable “magic pad.” represents how likely you are Four years earlier she had transitioned from hearing loss to complete deafness by giving up to ﬁ nd questions about that her now useless hearing aids. system on the AP® exam. More pages are devoted to vision than “Do you hear anything?” I wrote. hearing, and vision questions are “No,” she answered, her voice still strong although she could not hear it. “Last night somewhat more likely to appear your Dad came in and found the TV blasting. Someone had left the volume way up; I on the exam. didn’t hear a thing.” (Indeed, my father later explained, he recently tested her by sneak- ing up while she was reading and giving a loud clap just behind her ear. Her eye never wavered from the page.) What is it like, I wondered. “A silent world?” “Yes,” she replied. “It’s a silent world.”

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And for her, with human connections made diffi cult, it became a socially isolated world. “Not having understood what was said in a group,” she reminisced, “I would chime in and say the same thing someone else had just said—and everyone would laugh. I would be so embarrassed, I wanted to fall through the fl oor.” Increasingly, her way of coping was to avoid getting out onto the fl oor in the fi rst place. She shied away from public events and found excuses to avoid people who didn’t understand. Our exchange left me wondering: Will I—having inherited her progressive hearing loss—also become socially isolated? Or, aided by today’s better technology, can I keep my private vow not to repeat her past? Hearing allows mind-to-mind communication and en- The sounds of music A violin’s ables connection. Yet many of us can and do connect despite hearing loss—with help from short, fast waves create a high pitch, technology, lip-reading, and signing. For me, it’s worth the effort. Communicating with oth- a cello’s longer, slower waves a lower ers affi rms our humanity as social creatures. pitch. Differences in the waves’ height, So, how does hearing normally work? How do we harvest meaning from the air pres- or amplitude, also create differing degrees of loudness. (To review the sure waves sent from another’s mouth? physical properties of light and sound waves, see Figure 18.2 in Module 18.) The Stimulus Input: Sound Waves Draw a bow across a violin, and you will unleash the energy of sound waves. Jostling molecules of air, each bumping into the next, create waves of compressed and expanded air, like the ripples on a pond circling out from a tossed stone. As we swim in our ocean of mov- Dennis MacDonald/Photo Edit ing air molecules, our ears detect these brief air pressure changes. ENGAGE (Exposed to a loud, low bass sound—perhaps from a bass guitar or a cello—we can also feel the vibration. We hear by both air and bone Applying Science conduction.) Have students measure the decibels of Like light waves, sound waves vary in shape. The amplitude of sound waves determines their loudness. Their length, or frequency, diff erent sounds common to school: AP® Exam Tip determines the pitch we experience. Long waves have low frequency—and low pitch. Short the bells that signal class changes, hall waves have high frequency—and high pitch. Sound waves produced by a violin are much Note that both light and sound travel in waves. In each case, noise, and diff erent teachers’ voices. Do shorter and faster than those produced by a cello or a bass guitar. the amplitude and length of the We measure sounds in decibels, with zero decibels representing the absolute threshold waves are important. these sounds fall within the safe range for hearing. Every 10 decibels correspond to a tenfold increase in sound intensity. Thus, nor- of decibels? mal conversation (60 decibels) is 10,000 times more intense than a 20-decibel whisper. And frequency a temporarily tolerable 100-decibel passing subway train is 10 billion times more intense the number of complete wavelengths that pass a than the faintest detectable sound. point in a given time (for example, ENGAGE per second). pitch a tone’s experienced highness Active Learning The Ear or lowness; depends on frequency. Students can also demonstrate bone- The intricate process that transforms vibrating air into nerve impulses, which our brain middle ear the chamber between the eardrum and cochlea containing conducted sound with a metal coat decodes as sounds, begins when sound waves enter the outer ear. A mechanical chain three tiny bones (hammer, anvil, hanger tied to the center of a thin reaction begins as the visible outer ear channels the waves through the auditory canal to and stirrup) that concentrate the the eardrum, a tight membrane, causing it to vibrate (FIGURE 20.1 on the next page). In vibrations of the eardrum on the string about 4’ long. They should fi rst the middle ear three tiny bones (the hammer, anvil, and stirrup) pick up the vibrations cochlea’s oval window. press each end of the string into each and transmit them to the cochlea, a snail- shaped tube in the inner ear. The incoming cochlea [KOHK-lee - uh] a coiled, vibrations cause the cochlea’s membrane (the oval window) to vibrate, jostling the fl uid bony, fl uid - fi lled tube in the inner ear with the tips of the index fi ngers that fi lls the tube. This motion causes ripples in the basilar membrane, bending the hair ear; sound waves traveling through the cochlear fl uid trigger nerve while plugging their ears. Then they cells lining its surface, not unlike the wind bending a wheat fi eld. Hair cell movement impulses. triggers impulses in the adjacent nerve cells. Axons of those cells converge to form the should ask someone to tap the coat inner ear the innermost part of auditory nerve, which sends neural messages (via the thalamus) to the auditory cortex in the ear, containing the cochlea, hanger with a knife or fork. John Fisher the brain’s temporal lobe. From vibrating air to fl uid waves to electrical impulses to the semicircular canals, and vestibular reports that the eff ect will sound like brain: Voila! We hear. sacs. the city of London’s famous clock Big Ben.

MyersAP_SE_2e_Mod20_B.indd 194 1/21/14 9:33 AM MyersAP_SE_2e_Mod20_B.inddENGAGE 195 1/21/14 9:33 AM Enrichment The technical name for the collection of bones in the middle ear is ossicles. Each bone also has a technical name: hammer—malleus anvil—incus stirrups—stapes

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ENGAGE (a) OUTER EAR MIDDLE EAR INNER EAR Enrichment Semicircular canals Why does our own voice sound unfa- Bones of the middle ear Bone miliar when we hear it on tape? When Auditory nerve we listen to ourselves speak, we hear Sound both the sound conducted by airwaves waves Cochlea to the outer ear and that sound carried directly to the auditory nerve by Eardrum Auditory Oval window bone conduction. The latter is easily canal (where stirrup attaches) demonstrated by clicking the teeth or Cochlea, Auditory cortex munching popcorn, or by striking the Hammer Anvil partially uncoiled of temporal lobe prongs of a fork on a table and quickly applying its handle to the bone behind (b) Enlargement of middle ear the ear. An even more resounding and inner ear, showing Auditory nerve cochlea partially uncoiled Sound eﬀ ect will be produced if the fork’s for clarity waves Nerve fibers to auditory nerve handle is clenched between the teeth. Protruding hair cells Basilar membrane Figure 20.1 The strictly air-conducted sound that Eardrum Stirrup Motion of fluid in the cochlea Hear here: How we transform Oval window others normally hear (like a sound sound waves into nerve impulses that our brain we hear when our voice is on tape) is interprets (a) The outer ear funnels sound waves to the eardrum. The My vote for the most intriguing part of the hearing process is the hair cells—“quivering thinner. Students can hear the sound bones of the middle ear (hammer, bundles that let us hear” thanks to their “extreme sensitivity and extreme speed” (Goldberg, waves conducted by bone if they plug anvil, and stirrup) amplify and relay the eardrum’s vibrations through 2007). A cochlea has 16,000 of them, which sounds like a lot until we compare that with an their ears and talk in a normal voice. the oval window into the fluid -filled eye’s 130 million or so photoreceptors. But consider their responsiveness. Deﬂ ect the tiny cochlea. (b) As shown in this detail of bundles of cilia on the tip of a hair cell by the width of an atom—the equivalent of displacing the middle and inner ear, the resulting Fisher, J. (1979). Body magic. New York: Stein pressure changes in the cochlear the top of the Eiffel Tower by half an inch—and the alert hair cell, thanks to a special protein and Day. fluid cause the basilar membrane to at its tip, triggers a neural response (Corey et al., 2004). ripple, bending the hair cells on its surface. Hair cell movements trigger impulses at the base of the nerve cells, whose fibers converge to form the auditory nerve. That nerve sends neural messages to the thalamus and on to the auditory cortex. Susumu Nishinaga/Science Source

Be kind to your inner ear’s hair cells When vibrating in response to sound, the hair cells shown here lining the cochlea produce an electrical signal.

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Damage to the cochlea’s hair cell receptors or their associated nerves can cause sensorineural hearing loss (or nerve deafness). (A less common form of hearing loss sensorineural hearing loss ENGAGE hearing loss caused by damage to is conduction hearing loss, caused by damage to the mechanical system that con- the cochlea’s receptor cells or to the Enrichment ducts sound waves to the cochlea.) Occasionally, disease causes sensorineural hearing auditory nerves; also called nerve loss, but more often the culprits are biological changes linked with heredity, aging, and deafness. People who are deaf due to a defect prolonged exposure to ear-splitting noise or music. conduction hearing loss hearing in either the inner or middle ear may Hair cells have been likened to carpet ﬁ bers. Walk around on them and they will loss caused by damage to the spring back with a quick vacuuming. But leave a heavy piece of furniture on them for mechanical system that conducts still be able to hear by bone conduc- a long time and they may never rebound. As a general rule, if we cannot talk over a sound waves to the cochlea. tion. When Beethoven became deaf, he noise, it is potentially harmful, especially if prolonged and repeated (Roesser, 1998). Such experiences are common when sound exceeds 100 decibels, as happens in could still hear a piano being played

venues from frenzied sports arenas to bagpipe bands to personal music That Baylen may hear When by placing one end of his walking stick coming through our earphones near maximum volume (FIGURE 20.2). Super Bowl-winning quarterback Drew against it and gripping the other end Ringing of the ears after exposure to loud machinery or music Brees celebrated New Orleans’ 2010 indicates that we have been bad to our unhappy hair cells. victory amid pandemonium, he used between his teeth. To determine the ear muffs to protect the vulnerable hair As pain alerts us to possible bodily harm, ringing of the cells of his son, Baylen. nature and degree of their hearing loss, ears alerts us to possible hearing damage. It is hearing’s equivalent of bleeding. deaf violinists reportedly applied their The rate of teen hearing loss, now 1 in 5, has risen teeth to some part of their vibrating by one-third since the early 1990s (Shargorodsky et al., instruments. If they could not hear 2010). Teen boys more than teen girls or adults blast themselves with loud volumes for long periods (Zogby, 2006). sound, they concluded that the audi- Males’ greater noise exposure may help explain why men’s tory nerves were the problem and the hearing tends to be less acute than women’s. But male or deafness was past cure. female, those who spend many hours in a loud nightclub, behind a power mower, or above a jackhammer should wear earplugs. “Condoms or, safer yet, abstinence,” say sex educa- ENGAGE tors. “Earplugs or walk away,” say hearing educators. AP Photo/Mark J. Terrill Active Learning Loud music is often associated with teens, but how much dangerously loud Decibels 140 Rock band (amplified) Prolonged Figure 20.2 at close range exposure noise are teens exposed to on a daily 130 above 85 The intensity of some common sounds decibels basis? Explore the following questions: 120 Loud thunder produces hearing 110 Jet plane at 500 feet loss. How loud (in decibels) are the 100 Subway train at 20 feet different levels of volume on 90 a typical MP3 player? Do the 80 Busy street corner manufacturers provide this 70 information? Why or why not? 60 Normal conversation 50 Survey a group of teens who 40 listen to MP3 players. At what 30 level, on average, do they listen to 20 Whisper their music? 10 How loud is a typical concert? What 0 Threshold of hearing

Mark Holloway/Getty Images do musicians do today to protect their hearing? Should concert promoters offer earplugs at the door of concerts? Why or why not?

MyersAP_SE_2e_Mod20_B.indd 196 1/21/14 9:33 AM MyersAP_SE_2e_Mod20_B.inddENGAGE 197 1/21/14 9:33 AM Active Learning People in the Deaf community are divided over What are the benefits and limitations the roles of speech and sign language when of using sign language exclusively in a communicating with the hearing world. Some hearing world? in the community believe that learning to What should the hearing world’s response speak and read lips instead of learning sign lan- be to the use of sign language? guage denies one’s identity as a Deaf person. Consider the following questions:

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Hardware for hearing Cochlear implants TEACH work by translating sounds into electrical signals that are transmitted to the cochlea and, Flip It via the auditory nerve, on to the brain. Transmitter Students can get some additional help understanding hearing by watching the Flip It Video: Theories of Hearing. Receiver/Stimulator Electrode

Speech processor

For now, the only way to restore hearing for people with nerve deafness is a sort of cochlear implant a device for converting sounds into electrical bionic ear—a cochlear implant, which, by 2009, had been given to 188,000 people world- signals and stimulating the auditory wide (NIDCD, 2011). This electronic device translates sounds into electrical signals that, nerve through electrodes threaded wired into the cochlea’s nerves, convey information about sound to the brain. Cochlear into the cochlea. implants given to deaf kittens and human infants seem to trigger an “awakening” of the pertinent brain area (Klinke et al., 1999; Sirenteanu, 1999). They can help children become profi cient in oral communication (especially if they receive them as preschoolers or even before age 1) (Dettman et al., 2007; Schorr et al., 2005). The latest cochlear implants also can help restore hearing for most adults. However, the implants will not enable normal hearing in adults if their brain never learned to process sound during childhood. Similarly, cochlear implants did not enable hearing in deaf-from-birth cats that received them when fully grown rather than as 8-week-old kittens (Ryugo et al., 2010). Perceiving Loudness How do we detect loudness? It is not, as I would have guessed, from the intensity of a FYI hair cell’s response. Rather, a soft, pure tone activates only the few hair cells attuned to its frequency. Given louder sounds, neighboring hair cells also respond. Thus, the brain can Experiments are also under way to restore vision—with a bionic retina interpret loudness from the number of activated hair cells. (a 2-millimeter - diameter microchip If a hair cell loses sensitivity to soft sounds, it may still respond to loud sounds. This helps with photoreceptors that stimulate explain another surprise: Really loud sounds may seem loud to people with or without normal damaged retinal cells), and with a hearing. As a person with hearing loss, I used to wonder what really loud music must sound video camera and computer that stimulate the visual cortex. In test like to people with normal hearing. Now I realize it sounds much the same; where we differ is trials, both devices have enabled in our sensation of soft sounds. This is why we hard- of - hearing people do not want all sounds blind people to gain partial sight (loud and soft) amplifi ed. We like sound compressed—which means harder - to - hear sounds are (Boahen, 2005; Steenhuysen, 2002). amplifi ed more than loud sounds (a feature of today’s digital hearing aids). TEACH Perceiving Pitch

Common Pitfalls 20-220-2 What theories help us understand pitch perception?

Students may get the 2 theories of How do we know whether a sound is the high - frequency, high - pitched chirp of a bird or the hearing confused: low - frequency, low - pitched roar of a truck? Current thinking on how we discriminate pitch, like current thinking on how we discriminate color, combines two theories. In place theory, different frequencies of sound waves are said to vibrate different places on the cochlea. These places are wired to different parts of the auditory cortex in the brain so the sound can be ENGAGEMyersAP_SE_2e_Mod20_B.indd 198 1/21/14 9:33 AM MyersAP_SE_2e_Mod20_B.indd 199 1/21/14 9:33 AM processed correctly. Enrichment In frequency theory, the entire cochlea is believed to vibrate at a Heather Whitestone McCallum, Miss Alabama Her choices to use speech over sign language particular frequency, thus sending 1995, was crowned Miss America in 1995 and and to receive a cochlear implant have been the signal of the quality of sound to has been profoundly deaf since childhood. Her controversial in the Deaf community. the brain. talent for the competition was ballet, which she learned to do well by feeling the vibrations of the music through the ﬂ oor on which she danced. In 2002, she received a cochlear implant to enhance her sense of hearing. She chose to have this done when she could not hear her young son’s cries after he injured himself playing in the yard at their home.

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• Hermann von Helmholtz’s place theory presumes that we hear different pitches because different sound waves trigger activity at different places along place theory in hearing, the ENGAGE theory that links the pitch we hear the cochlea’s basilar membrane. Thus, the brain determines a sound’s pitch with the place where the cochlea’s Active Learning by recognizing the specific place (on the membrane) that is generating the membrane is stimulated. neural signal. When Nobel laureate- to - be Georg von Békésy (1957) cut holes frequency theory in hearing, the Invite a volunteer to sit with eyes in the cochleas of guinea pigs and human cadavers and looked inside with theory that the rate of nerve impulses closed in a chair facing the class. a microscope, he discovered that the cochlea vibrated, rather like a shaken traveling up the auditory nerve bedsheet, in response to sound. High frequencies produced large vibrations matches the frequency of a tone, thus Clap at varying locations around the near the beginning of the cochlea’s membrane. Low frequencies vibrate more enabling us to sense its pitch. volunteer’s head. The person will con- of the membrane, including near the end. But a problem remains: Place theory can explain how we hear high- pitched sounds but not low- pitched sounds. The fi dently and accurately locate sounds neural signals generated by low-pitched sounds are not so neatly localized on coming from either side (which strike the basilar membrane. the 2 ears diff erently), but will have • Frequency theory suggests an alternative: The brain reads pitch by monitoring the frequency of neural impulses traveling up the auditory nerve. The whole basilar more diffi culty locating sound in the membrane vibrates with the incoming sound wave, triggering neural impulses to 360° plane equidistant between the the brain at the same rate as the sound wave. If the sound wave has a frequency of 2 ears (overhead, in back, or in front). 100 waves per second, then 100 pulses per second travel up the auditory nerve. But again, a problem remains: An individual neuron cannot fi re faster than 1000 times per second. How, then, can we sense sounds with frequencies above 1000 waves per TEACH second (roughly the upper third of a piano keyboard)? • Enter the volley principle: Like soldiers who alternate fi ring so that some can shoot Teaching Tip while others reload, neural cells can alternate fi ring. By fi ring in rapid succession, they Ask students why dogs cock their can achieve a combined frequency above 1000 waves per second. Thus, place theory best explains how we sense high pitches, frequency theory best explains how we sense low heads to one side or another when pitches, and some combination of place and frequency seems to handle the pitches in they listen to sounds. Explain that dogs the intermediate range. and other animals do that to identify Locating Sounds the direction of the sound and hear it

20-320-3 How do we locate sounds? better. Why don’t we have one big ear—perhaps above our one nose? “All the better to hear you ENGAGE with,” as the wolf said to Red Riding Hood. As the placement of our eyes allows us to sense visual depth, so the placement of our two ears allows us to enjoy stereophonic (“three - Active Learning dimensional”) hearing. Two ears are better than one for at least We localize sound by detecting small two reasons. If a car to the right honks, your Figure 20.3 diff erences in the loudness and timing right ear receives a more intense sound, and How we locate it receives sound slightly sooner than your sounds Sound waves of the sounds received by the 2 ears. left ear (FIGURE 20.3). Because sound strike one ear sooner and Air more intensely than the Using a 4’ length of fl exible plastic tub- travels 750 miles per hour and our ears are other. From this information, ing or hose have a student hold each but 6 inches apart, the intensity difference our nimble brain computes and the time lag are extremely small. A just the sound’s location. As end of the tube up to each ear, while you might therefore expect, noticeable difference in the direction of people who lose all hearing the circle formed is kept down and in two sound sources corresponds to a time in one ear often have difference of just 0.000027 second! Lucky difficulty locating sounds. front of the body. Another person then Sound for us, our supersensitive auditory system shadow taps the tube with a pencil. A sound can detect such minute differences (Brown wave will move in both directions to & Deffenbacher, 1979; Middlebrooks & Green, 1991). the ears. If the tube is tapped at any point other than the middle, the sound will reach the 2 ears at diff erent times. Thus, the sound will seem to come from diff erent directions as diff erent spots on the tube are struck. The per- MyersAP_SE_2e_Mod20_B.indd 198 1/21/14 9:33 AM MyersAP_SE_2e_Mod20_B.indd 199 1/21/14 9:33 AM ceived direction of a sound is related to diff erences in the time at which the sound is received by each ear. Coren, S., Ward, L. M., & Enns, J. T. (1999). Sensation and perception (5th ed.). Fort Worth, TX: Harcourt Brace.

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CLOSE & ASSESS Before You Move On ᭤ ASK YOURSELF Exit Assessment If you are a hearing person, imagine that you had been born deaf. Do you think your life Provide students with a diagram of would be different? Figure 20.1 and have students label the ᭤ TEST YOURSELF diagram and write an explanation of What are the basic steps in transforming sound waves into perceived sound? how the ear receives sound and trans- Answers to the Test Yourself questions can be found in Appendix E at the end of the book. fers it to the brain for processing.

Module 20 Review What are the characteristics of air pressure 20-1 20-220-2 What theories help us understand pitch waves that we hear as sound, and how perception? does the ear transform sound energy into neural messages? • Place theory explains how we hear high-pitched sounds, and frequency theory explains how we hear low-pitched • Sound waves are bands of compressed and expanded sounds. (A combination of the two theories (the volley air. Our ears detect these changes in air pressure and principle) explains how we hear pitches in the middle transform them into neural impulses, which the brain range.) decodes as sound. • Place theory proposes that our brain interprets a particular pitch by decoding the place where a sound Sound waves vary in amplitude, which we perceive as • wave stimulates the cochlea’s basilar membrane. differing loudness, and in frequency, which we experience • Frequency theory proposes that the brain deciphers as differing pitch. the frequency of the neural impulses traveling up the • The outer ear is the visible portion of the ear. The middle auditory nerve to the brain. ear is the chamber between the eardrum and cochlea. • The inner ear consists of the cochlea, semicircular canals, 20-320-3 How do we locate sounds? and vestibular sacs. • Through a mechanical chain of events, sound waves • Sound waves strike one ear sooner and more intensely traveling through the auditory canal cause tiny vibrations than the other. The brain analyzes the minute differences in the eardrum. The bones of the middle ear (the hammer, in the sounds received by the two ears and computes the anvil, and stirrup) amplify the vibrations and relay them to sound’s source. the fl uid-fi lled cochlea. Rippling of the basilar membrane, caused by pressure changes in the cochlear fl uid, causes movement of the tiny hair cells, triggering neural messages to be sent (via the thalamus) to the auditory cortex in the brain. • Sensorineural hearing loss (or nerve deafness) results from damage to the cochlea’s hair cells or their associated nerves. Conduction hearing loss results from damage to the mechanical system that transmits sound waves to the cochlea. Cochlear implants can restore hearing for some people.

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Multiple-Choice Questions Answers to Multiple-Choice 1. What type of hearing loss is due to damage to the 3. Which of the following reﬂ ects the notion that pitch Questions mechanism that transmits sound waves to the cochlea? is related to the number of impulses traveling up the a. Sensorineural auditory nerve in a unit of time? 1. c 3. b b. Window-related a. Place theory 2. d 4. d c. Conduction b. Frequency theory d. Cochlear c. Volley principle e. Basilar d. Sound localization e. Stereophonic hearing 2. Pitch depends on which of the following? 4. a. Amplitude of a sound wave The three small bones of the ear are located in the b. Number of hair cells stimulated a. cochlea. c. Strength of nerve impulses traveling up the auditory b. outer ear. nerve c. inner ear. d. Number of sound waves that reach the ear in a given d. middle ear. time e. auditory nerve. e. Decibels of a sound wave

Practice FRQs Answer to Practice FRQ 1. 2. Describe two parts of the ear that transmit sound waves What roles do the outer, middle, and inner ear play in 1 point: Outer ear: Hearing begins before they reach the hair cells. helping a person hear a song on the radio? (3 points) here where sound is funneled by the Answer ear down the auditory canal to the Students may describe any two of the following: eardrum, which is the tight membrane 1 point: The eardrum, a tight membrane separating the middle ear from the outer ear. that begins to vibrate. 1 point: The three bones in the middle ear that transmit 1 point: Middle ear: This portion of the sound waves between the eardrum and the cochlea. ear receives the vibrations from the 1 point: The oval window, the point at which vibrations enter the cochlea. eardrum and sends them to the 3 tiny 1 point: The cochlea, where the ﬂ uid inside vibrates and the bones (hammer, anvil, and stirrup), and hair cells are stimulated. passes the vibrations to the cochlea’s oval window. 1 point: Inner ear: The sound travels through the semicircular canal to the cochlea. The cochlea converts sound pressure impulses into electrical impulses, which are transmitted by the auditory nerve to the brain.

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TEACH TRMTRM Discussion Starter Module 21 Use the Module 21 Fact or Falsehood? student activity from the TRM to intro- The Other Senses duce the concepts from this module.

ENGAGE Module Learning Objectives Enrichment 21-121-1 Describe the sense of touch.

There are 2 types of skin, the largest 21-2 Discuss how we best understand and control pain. organ in the human body: © Paul Burns/Corbis 21-321-3 Describe the senses of taste and smell. Hairy skin contains hair cells, which detect movement and pressure. 21-421-4 Explain how we sense our body’s position and movement. Glabrous skin contains no hair cells, 21-5 Describe how our senses interact. so the receptors in this type of skin are more sensitive. Glabrous skin is found mainly on the palms of the hands, bottoms of the feet, and on lthough our brain gives seeing and hearing priority in the allocation of cortical tis- the lips. A sue, extraordinary happenings occur within our four other senses—our senses of touch, taste, smell, and body position and movement. Sharks and dogs rely on their ENGAGE extraordinary sense of smell, aided by large brain areas devoted to this system. Without our own senses of touch, taste, smell, and body position and movement, we humans TRMTRM Active Learning would also be seriously handicapped, and our capacities for enjoying the world would be seriously diminished. The skin senses variations of cold and warm which, when combined, make Touch something feel hot. Donald Mershon suggests a convenient demonstration 21-121-1 How do we sense touch? that utilizes an ice cube tray (one that Although not the fi rst sense to come to mind, touch is vital. Right from the start, touch makes the very small cubes). First fi ll is essential to our development. Infant rats deprived of their mother’s grooming produce less growth hormone and have a lower metabolic rate—a good way to keep alive until the every other row in either direction with “Touch is both the alpha and omega of affection.” -WILLIAM mother returns, but a reaction that stunts growth if prolonged. Infant monkeys allowed water and freeze. Then, being careful JAMES (1890) to see, hear, and smell—but not touch—their mother become desperately unhappy; those not to slop water to produce melting, separated by a screen with holes that allow touching are much less miserable. As we will see in Module 46, premature human babies gain weight faster and go home sooner if they fi ll the empty row with warm water. are stimulated by hand massage. As lovers, we yearn to touch—to kiss, to stroke, to snuggle. Have a student place his or her hand And even strangers, touching only the other’s forearms and separated by a curtain, can communicate anger, fear, disgust, love, gratitude, and sympathy at levels well above chance over the surface of the tray to feel (Hertenstein et al., 2006). the heat. Use Student Activity: Warm Humorist Dave Barry may be right to jest that your skin “keeps people from seeing the Plus Cold Equals Hot from the TRM to inside of your body, which is repulsive, and it prevents your organs from falling onto the ground.” But skin does much more. Our “sense of touch” is actually a mix of distinct skin further demonstrate this concept. senses for pressure, warmth, cold, and pain. Touching various spots on the skin with a soft

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hair, a warm or cool wire, and the point of a pin reveals that some spots are especially sensitive to pressure, others to warmth, others to cold, still others to pain. Other skin sensations Cold Warm are variations of the basic four (pressure, warmth, cold, and pain): water water

• Stroking adjacent pressure spots creates a tickle. HOT! • Repeated gentle stroking of a pain spot creates an itching sensation. • Touching adjacent cold and pressure spots triggers a sense of wetness, which you can experience by touching dry, cold metal. • Stimulating nearby cold and warm spots produces the sensation of hot (FIGURE 21.1). Touch sensations involve more than tactile stimulation, however. A self- produced tickle produces less somatosensory cortex activation than does the same tickle from something or someone else (Blakemore et al., 1998). (The brain is wise enough to be most sensitive to unexpected stimulation.)

Pain TEACH

21-221-2 How can we best understand and control pain? Figure 21.1 Concept Connections Warm + cold = hot When ice- Pain is mainly governed by nerves Be thankful for occasional pain. Pain is your body’s way of telling you something has gone cold water passes through one coil and comfortably warm water through wrong. Drawing your attention to a burn, a break, or a sprain, pain orders you to change your another, we perceive the combined known as “free nerve endings,” which behavior—“Stay off that turned ankle!” The rare people born without the ability to feel pain sensation as burning hot. are not directly connected to any spe- may experience severe injury or even die before early adulthood. Without the discomfort that makes us occasionally shift position, their joints fail from excess strain, and without the warnings cifi c nervous system. Pain seems to be of pain, the effects of unchecked infections and injuries accumulate (Neese, 1991). regulated within its own system, work- More numerous are those who live with chronic pain, which is rather like an “Pain is a gift” So said a doctor ing where needed to signal the body alarm that won’t shut off. The suffering of those with persistent or recurring studying 13-year-old Ashlyn Blocker. backaches, arthritis, headaches, and cancer- related pain, prompts two ques- Ashlyn has a rare genetic mutation that to a painful stimulus. Nervous systems tions: What is pain? How might we control it? prevents her feeling pain. At birth she didn’t cry. As a child, she ran around are discussed in more detail in Unit III. for two days on a broken ankle. Understanding Pain She has put her hands on a hot machine and burned the flesh off. ENGAGE Our pain experiences vary widely. Women are more pain sensitive And she has reached into boiling than men are (Wickelgren, 2009). Individual pain sensitivity varies, water to retrieve a dropped too, depending on genes, physiology, experience, attention, and spoon. “Everyone in my class Active Learning asks me about it, and I say, surrounding culture (Gatchel et al., 2007; Reimann et al., 2010). ‘I can feel pressure, but I can’t Some people are born without the Thus, feeling pain refl ects both bottom-up sensations and top- feel pain.’ Pain! I cannot feel it!” down processes. (Heckert, 2010). ability to feel pain. Although this may Jeff Riedel/Contour by Getty Images seem like a great condition to have, it is BIOLOGICAL INFLUENCES There is no one type of stimulus that triggers pain (as light triggers actually horribly tragic. To understand vision). Instead, there are different nociceptors—sensory receptors that the situation, explore the following detect hurtful temperatures, pressure, or chemicals (FIGURE 21.2 on questions in a class discussion: the next page). Although no theory of pain explains all available fi ndings, psy- Why would it be bad not to feel chologist Ronald Melzack and biologist Patrick Wall’s (1965, 1983) clas- gate - control theory the theory pain? (Pain allows us to determine sic gate - control theory provides a useful model. The spinal cord con- that the spinal cord contains a neurological “gate” that blocks pain injury, sickness, and danger.) tains small nerve fi bers that conduct most pain signals, and larger fi bers signals or allows them to pass on to that conduct most other sensory signals. Melzack and Wall theorized the brain. The “gate” is opened by What might be the expected that the spinal cord contains a neurological “gate.” When tissue is in- the activity of pain signals traveling jured, the small fi bers activate and open the gate, and you feel pain. up small nerve fi bers and is closed life span of someone who can’t Large - fi ber activity closes the gate, blocking pain signals and preventing by activity in larger fi bers or by feel pain? (People born with this information coming from the brain. them from reaching the brain. Thus, one way to treat chronic pain is to condition do not generally live long past the teen years. They often die of normally painful illnesses that they don’t feel.) MyersAP_SE_2e_Mod21_B.indd 202 1/21/14 9:33 AM MyersAP_SE_2e_Mod21_B.inddENGAGE 203 1/21/14 9:33 AM TEACH Enrichment Flip It The gate-control theory of pain helps explain told what to expect following surgery and to why people aren’t always aware of pain. Pain relax to reduce their pain, they needed fewer Students can get some additional help signals can be controlled by the brain. The painkillers and were sent home 2. 7 days earlier understanding pain by watching the brain can sometimes choose which pain to than a control group. Research also indicates Flip It Video: Theories of Pain. consider and which to ignore, blocking off pain that up to 35% of patients with pathological signals in the spinal cord that it chooses to pain obtain relief from a placebo that contains ignore. This theory explains why pain is related no active ingredients. These examples show to the severity of the injury incurred and why that there is more to pain than what stimulates athletes can ignore major injuries. Research the sense receptors. indicates that when surgical patients were

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Figure 21.2 ENGAGE The pain circuit Sensory receptors (nociceptors) respond to potentially damaging stimuli by sending an Enrichment impulse to the spinal cord, which passes the message to the brain, The gate-control theory of pain may which interprets the signal as pain. explain why acupuncture works. Acupuncture is the ancient Chinese Projection practice of inserting needles into the to brain skin at certain points to alleviate pain.

This practice may work because the Cross-section of Pain the spinal cord needles create a competing sensation impulse that blocks the pain signals. The brain Cell body of could also be releasing endorphins to nociceptor counteract the numerous pain sensa- Nerve tions that acupuncture creates, thus cell alleviating pain.

TEACH Tissue injury Concept Connections Refer students to the Unit III dis- stimulate (by massage, electric stimulation, or acupuncture) “gate - closing” activity in the large neural fi bers (Wall, 2000). cussion of endorphins, the body’s But pain is not merely a physical phenomenon of injured nerves sending impulses to a natural painkillers. These endogenous defi nable brain area—like pulling on a rope to ring a bell. Melzack and Wall noted that brain- morphines work to alleviate pain and to - spinal - cord messages can also close the gate, helping to explain some striking infl uences on pain. When we are distracted from pain (a psychological infl uence) and soothed by the inhibit substance P, the body’s pain release of our naturally painkilling endorphins (a biological infl uence), our experience of pain neurotransmitter. diminishes. Sports injuries may go unnoticed until the after - game shower. People who carry a gene that boosts the availability of endorphins are less bothered by pain, and their brain is less responsive to pain (Zubieta et al., 2003). Others carry a mutated gene that disrupts pain circuit ENGAGE neurotransmission and experience little pain (Cox et al., 2006). Such discoveries may point the way toward new pain medications that mimic these genetic effects. Enrichment The brain can also create pain, as it does in people’s experiences of phantom limb sensations, when it misinterprets the spontaneous central nervous system activity that occurs in Phantom limb sensations occur when the absence of normal sensory input. As the dreamer may see with eyes closed, so some 7 a person feels the presence of a limb in 10 amputees may feel pain or movement in nonexistent limbs (Melzack, 1992, 2005). (An amputee may also try to step off a bed onto a phantom limb or to lift a cup with a phantom after it has been lost. At times, people hand.) Even those born without a limb sometimes perceive sensations from the absent arm can experience intense pain in a limb or leg. The brain, Melzack (1998) surmises, comes prepared to anticipate “that it will be get- that is no longer there. Contact a sur- ting information from a body that has limbs.” A similar phenomenon occurs with other senses. People with hearing loss often experi- geon who specializes in amputations ence the sound of silence: phantom sounds—a ringing- in - the - ears sensation known as tin- to come in and discuss how doctors nitus. Those who lose vision to glaucoma, cataracts, diabetes, or macular degeneration may experience phantom sights—nonthreatening hallucinations (Ramachandran & Blakeslee, treat patients with phantom limb pain 1998). Some with nerve damage have had taste phantoms, such as ice water seeming sick- and sensations. eningly sweet (Goode, 1999). Others have experienced phantom smells, such as nonexistent rotten food. The point to remember: We feel, see, hear, taste, and smell with our brain, which can sense even without functioning senses.

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PSYCHOLOGICAL INFLUENCES TEACH The psychological effects of distraction are clear in the stories of athletes who, focused on winning, play through the pain. We also seem to edit our memories of pain, which often differ Concept Connections from the pain we actually experienced. In experiments, and after medical procedures, people overlook a pain’s duration. Their memory snapshots instead record two factors: their pain’s Link our perception of pain to the fol-

peak moment (which can lead them to recall variable pain, with peaks, as worse [Stone et ERNST/Reuters/Corbis JONATHAN lowing concepts from other units: al., 2005]), and how much pain they felt at the end. In one experiment, researchers asked people to immerse one hand in painfully cold From Unit VII: Pain can be water for 60 seconds, and then the other hand in the same painfully cold water for 60 sec- remembered differently depending onds followed by a slightly less painful 30 seconds more (Kahneman et al., 1993). Which experience would you expect to recall as most painful? Curiously, when asked which trial on our moods, according to mood- they would prefer to repeat, most preferred the longer trial, with more net pain—but congruent memory. If we are in a less pain at the end. Physicians have used this principle with patients undergoing colon Playing with pain In a 2012 NFL game, Dallas Cowboys quarterback Tony good mood when we experience exams—lengthening the discomfort by a minute, but lessening its intensity (Kahneman, Romo cracked a rib after colliding with 1999). Although the extended milder discomfort added to their net pain experience, pa- an opposing player. He continued playing pain, our memories of it may not be tients experiencing this taper-down treatment later recalled the exam as less painful than through the pain, which reclaimed his negative. attention after the game’s end. did those whose pain ended abruptly. (If, at the end of a painful root canal, the oral sur- geon asks if you’d like to go home or to have a few more minutes of milder discomfort, From Unit XIV: Cultural differences there’s a case to be made for prolonging your hurt.) “When belly with bad pains doth affect how we perceive pain, or swell, It matters naught what else SOCIAL-CULTURAL INFLUENCES goes well.” -SADI, THE GULISTAN, 1258 what type of pain we may perceive Our perception of pain also varies with our social situation and our cultural traditions. We as being negative. If we know pain tend to perceive more pain when others also seem to be experiencing pain (Symbaluk et al., “Pain is increased by attending to is coming, and if we expect it to be 1997). This may help explain other apparent social aspects of pain, as when pockets of Aus- it.” -CHARLES DARWIN, EXPRESSION OF part of a growth experience, we tralian keyboard operators during the mid - 1980s suffered outbreaks of severe pain during EMOTIONS IN MAN AND ANIMALS, 1872 typing or other repetitive work—without any discernible physical abnormalities (Gawande, may not be bothered by it. 1998). Sometimes the pain in sprain is mainly in the brain—literally. When feeling empathy for another’s pain, a person’s own brain activity may partly mirror that of the other’s brain in pain (Singer et al, 2004). TEACH Thus, our perception of pain is a biopsychosocial phenomenon (FIGURE 21.3). View- ing pain this way can help us better understand how to cope with pain and treat it. Teaching Tip Reinforce the biopsychosocial approach with students by using Figure 21.3 Biological influences: Psychological influences: Biopsychosocial approach to Figure 21.3. Students should leave • activity in spinal cord’s large and small fibers • attention to pain pain Our experience of pain is much • genetic differences in endorphin production • learning based on experience AP® Psychology knowing that psycho- more than neural messages sent to • the brain’s interpretation of CNS activity • expectations the brain. logical phenomena are complex and inﬂ uenced by multiple variables.

Barros and Barros/Getty Images Pojoslaw/Shutterstock

Social-cultural influences: • presence of others • empathy for others’ pain • cultural expectations PersonalPersonal experiencee of pain Getty Images Robert Nickelsberg/

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TEACH Controlling Pain If pain is where body meets mind—if it is both a physical and a psychologi- Concept Connections cal phenomenon—then it should be treatable both physically and psycho-

Gary Conner/Phototake logically. Depending on the type of symptoms, pain control clinics select Remind students about the impor- one or more therapies from a list that includes drugs, surgery, acupuncture, tance of placebos in research, as electrical stimulation, massage, exercise, hypnosis, relaxation training, and discussed in Unit II. Having a “fake” thought distraction. Even an inert placebo can help, by dampening the central nervous treatment for your control condition system’s attention and responses to painful experiences—mimicking an- (or at least a treatment that mimics algesic drugs (Eippert et al., 2009; Wager, 2005). After being injected in the the status quo) helps ensure that just jaw with a stinging saltwater solution, men in one experiment received a placebo said to relieve pain, and they immediately felt better. Being given getting treatment is not causing a dif- fake pain-killing chemicals caused the brain to dispense real ones, as indi- ference in groups. cated by activity in an area that releases natural pain-killing opiates (Scott et al., 2007; Zubieta et al., 2005). “Believing becomes reality,” noted one commentator (Thernstrom, 2006), as “the mind unites with the body.” Acupuncture: A jab well Another experiment pitted two placebos—fake pills and pretend acupuncture—against TEACH done This acupuncturist is attempting to help this woman gain relief from each other (Kaptchuk et al., 2006). People with persistent arm pain (270 of them) received Concept Connections back pain by using needles on points either sham acupuncture (with trick needles that retracted without puncturing the skin) or of the patient’s hand. blue cornstarch pills that looked like pills often prescribed for strain injury. A fourth of those Some researchers believe that hypno- receiving the nonexistent needle pricks and 31 percent of those receiving the pills complained sis, discussed in Unit V, can be eﬀ ective of side effects, such as painful skin or dry mouth and fatigue. After two months, both groups in relieving pain. Others believe that were reporting less pain, with the fake acupuncture group reporting the greater pain drop. Distracting people with pleasant images (“Think of a warm, comfortable environment”) or hypnosis is just an elaborate way to drawing their attention away from the painful stimulation (“Count backward by 3s”) is an espe- distract people from obvious stimuli. cially effective way to activate pain-inhibiting circuits and to increase pain tolerance (Edwards Figure 21.4 Regardless of the method, diverting et al., 2009). A well - trained nurse may distract needle - shy patients by chatting with them and Virtual- reality pain control For asking them to look away when inserting the needle. For burn victims receiving excruciat- one’s attention from pain can be help- burn victims undergoing painful skin repair, an escape into virtual reality ing wound care, an even more effective distraction comes from immersion in a computer - ful in alleviating its eﬀ ects. can powerfully distract attention, thus generated 3-D world, like the snow scene in FIGURE 21.4. Functional MRI (fMRI) scans reducing pain and the brain’s response reveal that playing in the virtual reality reduces the brain’s pain - related activity (Hoffman, to painful stimulation. The fMRI 2004). Because pain is in the brain, diverting the brain’s attention may bring relief. scans on the right illustrate a lowered pain response when the patient is distracted.

TEACH Teaching Tip Point out that Dennis Turk and his No distraction colleagues have deﬁ ned 3 subtypes of people who are evaluated at pain centers. Image by Todd Richards and Aric Bills, U.W., © Hunter Hoffman, www.vrpain. com © Hunter Hoffman, www.vrpain. Richards and Aric Bills, U.W., Image by Todd com © Hunter Hoffman, www.vrpain. Richards and Aric Bills, U.W., Image by Todd com © Hunter Hoffman, www.vrpain. Richards and Aric Bills, U.W., Image by Todd Dysfunctional patients report high Distraction levels of pain and psychological distress, believe they have little control over their lives, and are extremely inactive. Interpersonally distressed patients

feel they have little social support TreatmentsMyersAP_SE_2e_Mod21_B.indd for pain 206 include hypnosis, acupunc- 1/21/14 9:34 AM MyersAP_SE_2e_Mod21_B.indd 207 1/21/14 9:34 AM and report that significant others ture, physiotherapy, ultrasound, biofeedback, don’t take their pain seriously. relaxation, and electrical stimulation. Many Adaptive copers report far less pain clinics also use some form of behavioral treat- and social distress than people in ment, which is based on the assumption that the other 2 groups and continue to pain has become a learned behavior pattern function at a relatively high level. that can be changed.

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Taste ENGAGE 21-321-3 How do we experience taste and smell? Enrichment Like touch, our sense of taste involves several basic sensations. Taste’s sensations were once According to Linda Bartoshuk, taste thought to be sweet, sour, salty, and bitter, with all others stemming from mixtures of these buds are innervated by 2 cranial four (McBurney & Gent, 1979). Then, as investigators searched for specialized nerve fi bers for the four taste sensations, they encountered a receptor for what we now nerves: one carries taste and the other The Survival know is a fi fth—the savory meaty taste of umami, best experienced as the fl avor en- Table 21.1 carries pain and touch. Supertasters Functions of Basic Tastes hancer monosodium glutamate (MSG), often used in Chinese and Thai food. perceive more pain from oral irritants Evolutionary psychologists explain that tastes exist for more than our pleasure Taste Indicates (see TABLE 21.1). Pleasureful tastes attracted our ancestors to energy- or protein- including chili peppers, ethyl alcohol, Sweet Energy source rich foods that enabled their survival. Aversive tastes deterred them from new foods and carbonation. Fat in food is also per- that might be toxic. We see the inheritance of this biological wisdom in today’s 2- to Salty Sodium essential to 6 - year - olds, who are typically fussy eaters, especially when offered new meats or physiological processes ceived as a touch sensation. If you’re a bitter - tasting vegetables, such as spinach and brussels sprouts (Cooke et al., 2003). supertaster, you’re a super perceiver of Sour Potentially toxic acid Meat and plant toxins were both potentially dangerous sources of food poisoning fat in food. for our ancestors, especially for children. Given repeated small tastes of disliked new Bitter Potential poisons foods, children will, however, typically begin to accept them (Wardle et al., 2003). Umami Proteins to grow and (Module 38 will explore cultural infl uences on our taste preferences.) repair tissue TEACH Taste is a chemical sense. Inside each little bump on the top and sides of your tongue are 200 or more taste buds, each containing a pore that catches food chemi- (Adapted from Cowart, 2005.) Common Pitfalls cals. Into each taste bud pore, 50 to 100 taste receptor cells project antenna-like hairs that sense food molecules. Some receptors respond mostly to sweet- tasting molecules, oth- The traditional “tongue map” showing ers to salty- , sour-, umami-, or bitter- tasting ones. It doesn’t take much to trigger a response how diff erent regions of the tongue that alerts your brain’s temporal lobe. If a stream of water is pumped across your tongue, the detect diff erent tastes is not accurate. addition of a concentrated salty or sweet taste for but one- tenth of a second will get your attention (Kelling & Halpern, 1983). When a friend asks for “just a taste” of your soft drink, In the late 1800s, a German doctoral you can squeeze off the straw after a mere instant. student studied the tongue’s sensitiv- Taste receptors reproduce themselves every week or two, so when you burn your tongue with hot pizza, it hardly matters. However, as you grow older, the number of taste buds de- ity to diff erent tastes, which he plotted creases, as does taste sensitivity (Cowart, 1981). (No wonder adults enjoy strong- tasting on a graph. The graph of his data was foods that children resist.) Smoking and alcohol use accelerate these declines. Those done “impressionistically,” meaning he who lose their sense of taste report that food tastes like “straw” and is hard to swallow (Cowart, 2005). didn’t rely on his actual data to create Essential as taste buds are, there’s more to taste than meets the tongue. the graph. For over 75 years, scholars Expectations can infl uence taste. When told a sausage roll was “vegetar- took his graph at face value, perpetuat- ian,” people in one experiment found it decidedly inferior to its identical partner labeled “meat” (Allen et al., 2008). In another experiment, when ing the myth of the tongue map. adults were told that a wine cost $90 rather than its real $10 price, they reported it tasting better and a brain area that responds to pleasant experiences showed more activity (Plassmann et al., 2008). Lauren Burke/Jupiterimages ENGAGE TRMTRM Active Learning Smell Try This Have students count the number of Life begins with an inhale and ends with an exhale. Between birth and death, you will daily Impress your friends with your new word for the day: People unable taste buds they have on their tongues. inhale and exhale nearly 20,000 breaths of life - sustaining air, bathing your nostrils in a to see are said to experience stream of scent- laden molecules. The resulting experiences of smell (olfaction) are strikingly blindness. People unable to hear Punch a hole in an index card and intimate: You inhale something of whatever or whoever it is you smell. experience deafness. People unable to smell experience place it on the tip of the tongue. Using Like taste, smell is a chemical sense. We smell something when molecules of a sub- anosmia. stance carried in the air reach a tiny cluster of 20 million receptor cells at the top of each blue food coloring, paint the tongue through the hole. Count the number of fungiform papillae (which will appear as bright pink bumps) in the hole. Supertasters will have many of these bumps, and nontasters will have few. MyersAP_SE_2e_Mod21_B.indd 206 1/21/14 9:34 AM MyersAP_SE_2e_Mod21_B.inddENGAGE 207 ENGAGE 1/21/14 9:34 AM Use Student Activity: Tasting Salt and Enrichment Enrichment Sugar from the TRM for another way to test for this ability. Psychologists Marcia Pelchat and Patricia Pliner In one study of infants, sweet substances elic- tested whether it is the novelty of a food or ited sucking and, in some cases, smiling. Sour something else that prompts people to spurn tastes produced “lip pursing and wrinkling of it. They gave 2 groups of people identical the nose,” and bitter tastes prompted “open- foods. When the foods were accurately named ing of the mouth with the upper lip elevated ( “chopped tomatoes” and “beefsteak” ), the and protrusion of the tongue.” These reactions participants were quite willing to taste them. make good evolutionary sense, because bitter When the foods were referred to as “pendula or sour plants are often toxic, whereas the fruit” and “langua steaks,” participants were far sweeter ones tend to be nutritious. less cooperative.

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Olfactory bulb TEACH 4. The signals are transmitted to higher Concept Connections regions of the brain.

As a link to neuroscience, inform Olfactory nerve students that smell is the only sense 3. The signals are relayed Olfactory bulb via converged axons. where the signals do not go directly to Receptor cells the thalamus before being processed. in olfactory Bone membrane In fact, smell is processed near the Olfactory prefrontal cortex before it is sent along, receptor cells 2. Olfactory receptor which may help explain why smell can cells are activated and send electric trigger powerful memories because signals. that part of the brain works with the limbic system to process emotional Odor molecules memories. 1. Odorants bind to receptors. ENGAGE Figure 21.5 Odorant The sense of smell If you are to receptor smell a flower, airborne molecules of its Enrichment fragrance must reach receptors at the Air with odorant molecules top of your nose. Sniffing swirls air up Can we tell if a person is male or female to the receptors, enhancing the aroma. on the basis of odor alone? Research The receptor cells send messages to the brain’s olfactory bulb, and then onward indicates that we can: to the temporal lobe’s primary smell nasal cavity (FIGURE 21.5). These olfactory receptor cells, waving like sea anemones on a cortex and to the parts of the limbic reef, respond selectively—to the aroma of a cake baking, to a wisp of smoke, to a friend’s system involved in memory and emotion. Patricia Wallace had blindfolded fragrance. Instantly, they alert the brain through their axon ﬁ bers. Being an old, primitive participants sniff a thoroughly sense, olfactory neurons bypass the brain’s sensory control center, the thalamus. washed hand, held ½" from their Research has shown that even nursing infants and their mothers have a literal chemistry to their relationship: They quickly learn to recognize each other’s scents (McCarthy, 1986). nose. They could discriminate male Aided by smell, a mother fur seal returning to a beach crowded with pups will ﬁ nd her own. from female hands with over 80% Our human sense of smell is less acute than our senses of seeing and hearing. Looking out accuracy. Female sniffers were more across a garden, we see its forms and colors in exquisite detail and hear a variety of birds singing, yet we smell little of it without sticking our nose into the blossoms. accurate than male sniffers. Odor molecules come in many shapes and sizes—so many, in fact, that it takes many Richard Doty and his colleagues different receptors to detect them. A large family of genes designs the 350 or so receptor proteins that recognize particular odor molecules (Miller, 2004). Linda Buck and Richard had college students assess Axel (1991) discovered (in work for which they received a 2004 Nobel Prize) that these breath odor of participants who receptor proteins are embedded on the surface of nasal cavity neurons. As a key slips into a lock, so odor molecules slip into these receptors. Yet we don’t seem to have a distinct sat on the other side of a partition receptor for each detectable odor. This suggests that some odors trigger a combination and exhaled through a plastic of receptors, in patterns that are interpreted by the olfactory cortex. As the English tube. Most judges scored better alphabet’s 26 letters can combine to form many words, so odor molecules bind to different receptor arrays, producing the 10,000 odors we can detect (Malnic et al., than chance, and again females 1999). It is the combinations of olfactory receptors, which activate different neu- outperformed males. ron patterns, that allow us to distinguish between the aromas of fresh- brewed and hours- old coffee (Zou et al., 2005). Mark Russel had first-year college For humans, the attractiveness of smells depends on learned associations

students wear T-shirts for 24 Tish1/Shutterstock (Herz, 2001). As babies nurse, their preference for the smell of their mother’s hours, after which the shirts were individually placed in sealed containers. Each participant was then presented with 3 containers: 1 holding his or her own shirt, a MyersAP_SE_2e_Mod21_B.indd 208 1/21/14 9:34 AM MyersAP_SE_2e_Mod21_B.indd 209 1/21/14 9:34 AM second holding the shirt of an unknown female, and a third holding the shirt of an unknown male. The vast majority were able to identify their own shirt and which other shirts belonged to a male or female.

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breast builds. So, too, with other associations. As good experiences are linked with a particular scent, people come to like that scent, which helps explain why ENGAGE people in the United States tend to like the smell of wintergreen (which they associate with candy and gum) more than do those in Great Britain (where Enrichment it often is associated with medicine). In another example of odors evoking Are there human pheromones? The unpleasant emotions, researchers frustrated Brown University students with a rigged computer game in a scented room (Herz et al., 2004). Later, if exposed most promising evidence comes from to the same odor while working on a verbal task, the students’ frustration was researchers investigating the men- AP Photo/The Charlotte Observer. Layne Bailey AP Photo/The Charlotte Observer. rekindled and they gave up sooner than others exposed to a different odor or strual “synchrony” in women who live no odor. Though it’s diffi cult to recall odors by name, we have a remarkable capacity to recog- The nose knows Humans have or work together. Martha McClintock some 20 million olfactory receptors. A nize long- forgotten odors and their associated memories (Engen, 1987; Schab, 1991). The bloodhound has 220 million (Herz, 2007). and Kathleen Stern recruited a group smell of the sea, the scent of a perfume, or an aroma of a favorite relative’s kitchen can of 29 women and asked 9 of them bring to mind a happy time. It’s a phenomenon the British travel agent chain Lunn Poly understood well. To evoke memories of lounging on to wear pads under their arms for sunny, warm beaches, the company once piped the Figure 21.6 Processes several hours, either before or just Taste, smell, and memory aroma of coconut suntan oil into its shops (Fracas- taste sini, 2000). Information from the taste buds after ovulation. When the pads were (yellow arrow) travels to an area Our brain’s circuitry helps explain an odor’s between the frontal and temporal then wiped under the noses of the power to evoke feelings and memories (FIGURE lobes of the brain. It registers in an other women, the results were star- 21.6). A hotline runs between the brain area re- area not far from where the brain receives information from our sense tling: Smelling pre-ovulation pads ceiving information from the nose and the brain’s of smell, which interacts with taste. ancient limbic centers associated with memory and The brain’s circuitry for smell (red shortened their menstrual cycles emotion. Thus, when put in a foul-smelling room, area) also connects with areas involved in memory storage, which by as many 14 days, whereas ovula- people expressed harsher judgments of immoral helps explain why a smell can trigger acts (such as lying or keeping a found wallet) and Processes smell a memory. tion phase pads increased cycles by more negative attitudes toward gay men (Inbar et (near memory area) as many as 12 days. McClintock is al., 2011; Schnall et al., 2008). continuing her research with an eye on possible applications. Pheromone Body Position and Movement treatments designed to regulate ovula- 21-421-4 How do we sense our body’s position and movement? tion could serve as fertility enhancers for couples who want to conceive and Important sensors in your joints, tendons, and muscles enable your kinesthesia—your sense of the position and movement of your body parts. By closing your eyes or plugging as contraceptives for those who don’t. your ears you can momentarily imagine being without sight or sound. But what would it be like to live without touch or kinesthetic sense—without, therefore, being able to sense the ENGAGE positions of your limbs when you wake during the night? Ian Waterman of Hampshire, Eng- land, knows. In 1972, at age 19, Waterman contracted a rare viral infection that destroyed Enrichment the nerves enabling his sense of light touch and of body position and movement. People with this condition report feeling disembodied, as though their body is dead, not real, not People who lose their kinesthetic theirs (Sacks, 1985). With prolonged practice, Waterman has learned to walk and eat—by sense, also called proprioception, lose visually focusing on his limbs and directing them accordingly. But if the lights go out, he crumples to the fl oor (Azar, 1998). Even for the rest of us, vision interacts with kinesthesia. the ability to move unless they can see Stand with your right heel in front of your left toes. Easy. Now close your eyes and you will kinesthesia [kin - ehs - THEE- themselves move. When they see their probably wobble. see-a] the system for sensing the position and movement of A companion vestibular sense monitors your head’s (and thus your body’s) posi- bodies, their brains are able to process individual body parts. tion and movement. The biological gyroscopes for this sense of equilibrium are in your in- what needs to be done to move. In the ner ear. The semicircular canals, which look like a three - dimensional pretzel (Figure 20.1a), vestibular sense the sense of body movement and position, dark, such individuals become limp and the vestibular sacs, which connect the canals with the cochlea, contain fl uid that moves including the sense of balance. when your head rotates or tilts. This movement stimulates hairlike receptors, which send and collapse.

MyersAP_SE_2e_Mod21_B.indd 208 1/21/14 9:34 AM MyersAP_SE_2e_Mod21_B.inddENGAGE 209 ENGAGE 1/21/14 9:34 AM Active Learning Active Learning Invite a local dance or fi gure skating instructor Our ability to maintain balance depends to to come to class to discuss how dancers and some extent on visual cues. Students can expe- fi gure skaters maintain their balance when rience this for themselves by standing on one completing those amazing spins and turns. foot for 30 seconds fi rst with their eyes open, then with their eyes closed. The latter is more diffi cult, because the vestibular and visual systems working together enable us to maintain balance. If students spin around a few times, thus disrupting their vestibular sense, and then close their eyes, they will fi nd it impossible to balance on one foot.

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messages to the cerebellum at the back of the brain, thus enabling you to ENGAGE sense your body position and to maintain your balance. If you twirl around and then come to an abrupt halt, neither the fl uid © Robert Kanavel Active Learning in your semicircular canals nor your kinesthetic receptors will immediately Myers suggests that the tastes of cer- return to their neutral state. The dizzy aftereffect fools your brain with the sensation that you’re still spinning. This illustrates a principle that underlies tain foods or drinks are indistinguish- perceptual illusions: Mechanisms that normally give us an accurate experi- able if smell is impaired. Have students ence of the world can, under special conditions, fool us. Understanding how test this by bringing in pieces of apple we get fooled provides clues to how our perceptual system works. and potato and cold coff ee and a sports drink. Using a blind taste test, Sensory Interaction have students plug their noses so that 21-521-5 How do our senses interact? no air can get into the nose and taste Our senses are not totally separate information channels. In interpreting the diff erent examples. They should Bodies in space These high school the world, our brain blends their inputs. Consider what happens to your not be able to tell the diff erence in the competitive cheer team members can sense of taste if you hold your nose, close your eyes, and have someone feed you various thank their inner ears for the information foods. A slice of apple may be indistinguishable from a chunk of raw potato. A piece of steak taste between the foods or drinks if that enables their brains to monitor their bodies’ position so expertly. may taste like cardboard. Without their smells, a cup of cold coffee may be hard to distin- smell is impaired. guish from a glass of Gatorade. To savor a taste, we normally breathe the aroma through our nose—which is why eating is not much fun when you have a bad cold. Smell can also change our perception of taste: A drink’s strawberry odor enhances our perception of its TEACH sweetness. Even touch can infl uence taste. Depending on its texture, a potato chip “tastes” TRMTRM Teaching Tip sensory interaction the fresh or stale (Smith, 2011). This is sensory interaction at work—the principle that one principle that one sense may sense may infl uence another. Smell + texture + taste = fl avor. Point out to students that vision and infl uence another, as when the Vision and hearing may similarly interact. An almost imperceptible fl icker of light is smell of food infl uences its taste. taste can also interact. Have students more easily visible when accompanied by a short burst of sound (Kayser, 2007). And a sound may be easier to hear with a visual cue. If I (as a person with hearing loss) watch a imagine how appetizing blue macaroni video with simultaneous captioning, I have no trouble hearing the words I am seeing (and and cheese might taste. Or perhaps may therefore think I don’t need the captioning). If I then turn off the captioning, I suddenly realize I do need it. The eyes guide the ears (FIGURE 21.7). have them consider the tastiness of But what do you suppose happens if the eyes and the ears disagree? What if we see a green mashed potatoes. Students may speaker saying one syllable while we hear another? Surprise: We may perceive a third syl- also expect that red-colored drinks lable that blends both inputs. Seeing the mouth movements for ga while hearing ba we may perceive da. This phenomenon is known may taste like strawberry or cherry Figure 21.7 as the McGurk effect, after its discoverers, fl avor, but may be startled if the taste is Sensory interaction psychologist Harry McGurk and his as- grape or orange. The color of our food When a hard- of -hearing sistant John MacDonald (1976). listener sees an animated Touch also interacts with our other and drink can infl uence our expecta- face forming the words being spoken at the other senses. In detecting events, the brain can tions of how it might taste. Use Teacher end of a phone line, the combine simultaneous touch and visual words become easier to signals, thanks to neurons projecting from Demonstration: Vision and Taste from understand (Knight, 2004). the somatosensory cortex back to the vi- The eyes guide the ears. the TRM to show how visual stimuli sual cortex (Macaluso et al., 2000). Touch can infl uence how we perceive taste even interacts with hearing. In one experiment, researchers blew a puff of air (such using gelatin. as our mouths produce when saying pa and ta) on the neck or hands as people heard either these sounds or the more air- less sounds ba or da. To my surprise (and

Courtesy of Action Hearing Loss yours?), the people more often misheard

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ba or da as pa or ta when played with the faint puff (Gick & Derrick, 2009). Thanks to sensory interaction, they were hearing with their skin. Our brain even blends our tactile and social judgments: • After holding a warm drink rather than a cold one, people are more likely to rate someone more warmly, feel closer to them, and behave more generously (IJzerman & Semin, 2009; Williams & Bargh, 2008). Physical warmth promotes social warmth. • After being given the cold shoulder by others in an experiment, people judge the room as colder than do those treated warmly (Zhong & Leonardelli, 2008). Social exclusion literally feels cold. • Holding a heavy rather than light clipboard makes job candidates seem more important. Holding rough objects makes social interactions seem more difﬁ cult (Ackerman et al., 2010). • When leaning to the left—by sitting in a left- rather than right-leaning chair, or squeezing a hand-grip with their left hand, or using a mouse with their left hand— people lean more left in their expressed political attitudes (Oppenheimer & Trail, 2010).

These examples of embodied cognition illustrate how brain circuits processing our bodily embodied cognition in sensations connect with brain circuits responsible for cognition. psychological science, the inﬂ uence So, the senses interact: As we attempt to decipher our world, our brain blends inputs of bodily sensations, gestures, and other states on cognitive from multiple channels. For many people, an odor, perhaps of mint or chocolate, can evoke preferences and judgments. a sensation of taste (Stevenson & Tomiczek, 2007). But in a few select individuals, the senses become joined in a phenomenon called synesthesia, where one sort of sensation (such as ENGAGE hearing sound) produces another (such as seeing color). Thus, hearing music may activate color- sensitive cortex regions and trigger a sensation of color (Brang et al., 2008; Hubbard et Online Activities al., 2005). Seeing the number 3 may evoke a taste sensation (Ward, 2003). * * * Students may ﬁ nd synesthesia interest- For a summary of our sensory systems, see TABLE 21.2. The river of perception is fed by ing. They can test whether they have sensation, cognition, and emotion. And that is why we need biological, psychological, and social-cultural levels of analysis. this condition by using the Synesthesia Battery on www.synesthete.org. Con- Table 21.2 Summarizing the Senses sider having students complete the Sensory System Source Receptors test to see what kinds of questions are

Vision Light waves striking the eye Rods and cones in the retina asked to assess such a condition.

Hearing Sound waves striking the outer Cochlear hair cells in the inner ear ear

Touch Pressure, warmth, cold, pain on Skin receptors detect pressure, the skin warmth, cold, and pain Touch Taste Taste Chemical molecules in the Basic tongue receptors for sweet, Hearing mouth sour, salty, bitter, and umami Smell Vision Smell Chemical molecules breathed in Millions of receptors at top of through the nose nasal cavity

Body position— Any change in position of a Kinesthetic sensors all over the kinesthesia body part, interacting with vision body

Body movement— Movement of ﬂ uids in the inner Hairlike receptors in the semi- vestibular sense ear caused by head/body circular canals and vestibular movement sacs

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* * * CLOSE & ASSESS To feel awe, mystery, and a deep reverence for life, we need look no further than our own perceptual system and its capacity for organizing formless nerve impulses into colorful Exit Assessment sights, vivid sounds, and evocative smells. As Shakespeare’s Hamlet recognized, “There are Choose one of the concepts below more things in Heaven and Earth, Horatio, than are dreamt of in your philosophy.” Within our ordinary sensory and perceptual experiences lies much that is truly extraordinary—sure- that are often misunderstood and have ly much more than has so far been dreamt of in our psychology. students provide an explanation of that concept: Before You Move On Gate-control theory of pain Kinesthesia vs. vestibular sense ᭤ ASK YOURSELF Have you ever experienced a feeling that you think could be explained by embodied Embodied cognition cognition? Synesthesia ᭤ TEST YOURSELF How does our system for sensing smell differ from our sensory systems for vision, touch, and taste? Answers to the Test Yourself questions can be found in Appendix E at the end of the book.

Module 21 Review

21-121-1 How do we sense touch? 21-3 How do we experience taste and smell?

• Our sense of touch is actually several senses—pressure, • Taste and smell are chemical senses. warmth, cold, and pain—that combine to produce other Taste is a composite of fi ve basic sensations—sweet, sour, sensations, such as “hot.” • salty, bitter, and umami—and of the aromas that interact with information from the taste receptor cells of the taste 21-2 How can we best understand and control pain? buds. • There are no basic sensations for smell. We have some 20 • Pain refl ects bottom-up sensations (such as input from million olfactory receptor cells, with about 350 different nociceptors, the sensory receptors that detect hurtful receptor proteins. temperatures, pressure, or chemicals) and top-down Odor molecules trigger combinations of receptors, in processes (such as experience, attention, and culture). • patterns that the olfactory cortex interprets. The receptor • One theory of pain is that a “gate” in the spinal cord cells send messages to the brain’s olfactory bulb, then to either opens to permit pain signals traveling up small the temporal lobe, and to parts of the limbic system. nerve fi bers to reach the brain, or closes to prevent their passage. 21-4 How do we sense our body’s position and movement? • The biopsychosocial perspective views our perception of pain as the sum of biological, psychological, and Through kinesthesia, we sense the position and movement social-cultural infl uences. Pain treatments often combine • of our body parts. physical and psychological elements, including placebos and distractions. • We monitor our body’s position and movement, and maintain our balance with our vestibular sense.

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21-5 How do our senses interact?

• Our senses can infl uence one another. This sensory • Embodied cognition is the infl uence of bodily sensations, interaction occurs, for example, when the smell of a gestures, and other states on cognitive preferences and favorite food amplifi es its taste. judgments.

Multiple-Choice Questions Answers to Multiple-Choice 1. Sensing the position and movement of individual body 3. Which of the following is the best example of sensory Questions parts is an example of which sense? interaction? a. Kinesthetic a. Finding that despite its delicious aroma, a weird- 1. a 3. b b. Vestibular looking meal tastes awful 2. e 4. a c. Auditory b. Finding that food tastes bland when you have a bad d. Umami cold e. Olfactory c. Finding it diffi cult to maintain your balance when you have an ear infection 2. Which of the following is the best example of d. Finding that the cold pool water doesn’t feel so cold kinesthesia? after a while a. Awareness of the smell of freshly brewed coffee e. All of these are examples. b. Ability to feel pressure on your arm 4. c. Ability to hear a softly ticking clock Which of the following is most closely associated with d. Ability to calculate where a kicked soccer ball will hairlike receptors in the semicircular canals? land from the moment it leaves your foot a. Body position e. Awareness of the position of your arms when b. Smell swimming the backstroke c. Hearing d. Pain e. Touch Practice FRQs Answer to Practice FRQ 2 1. 2. Describe the receptor cells for taste and smell. Briefl y explain the biopsychosocial perspective on pain 1 point: Pain is the sum of biologi- and pain treatment. Answer (2 points) cal, psychological, and social-cultural 1 point: Taste: Receptor cells in the tongue detect sweet, infl uences, depending on our brain’s sour, salty, bitter, and umami. interpretation of it, genetic diff er- 1 point: Smell: Olfactory cells line the top of the nasal cavity. ences, attention, expectations, presence of others, and empathy, among other things. 1 point: Treatment combines physical (drugs) and psychological (placebo and distraction) elements.

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Key Terms and Concepts to Remember sensation, p. 152 pupil, p. 172 monocular cues, p. 185 perception, p. 152 iris, p. 172 phi phenomenon, p. 185 bottom - up processing, p. 152 lens, p. 172 perceptual constancy, p. 186 top - down processing, p. 152 retina, p. 172 color constancy, p. 187 selective attention, p. 152 accommodation, p. 172 perceptual adaptation, p. 191 inattentional blindness, p. 154 rods, p. 173 audition, p. 194 change blindness, p. 154 cones, p. 173 frequency, p. 195 transduction, p. 155 optic nerve, p.173 pitch, p. 195 psychophysics, p. 155 blind spot, p. 173 middle ear, p. 195 absolute threshold, p. 156 fovea, p. 173 cochlea [KOHK-lee - uh], p. 195 signal detection theory, p. 156 feature detectors, p. 175 inner ear, p. 195 subliminal, p. 157 parallel processing, p. 176 sensorineural hearing loss, p. 197 priming, p. 157 Young - Helmholtz trichromatic (three - conduction hearing loss, p. 197 difference threshold, p. 158 color) theory, p. 178 cochlear implant, p. 198 Weber’s law, p. 158 opponent - process theory, p. 179 place theory, p. 199 sensory adaptation, p. 159 gestalt, p. 182 frequency theory, p. 199 perceptual set, p. 163 ﬁ gure - ground, p. 183 gate - control theory, p. 203 extrasensory perception (ESP), p. 167 grouping, p. 183 kinesthesia [kin - ehs - THEE-see-a], parapsychology, p. 167 depth perception, p. 184 p. 209 wavelength, p. 171 visual cliff, p. 184 vestibular sense, p. 209 hue, p. 172 binocular cues, p. 184 sensory interaction, p. 210 intensity, p. 172 retinal disparity, p. 184 embodied cognition, p. 211

Key Contributors to Remember Gustav Fechner, p. 156 David Hubel, p. 175 Ernst Weber, p. 158 Torsten Wiesel, p. 175

AP® Exam Practice Questions Answers to Multiple-Choice Multiple-Choice Questions Questions 1. What is the purpose of the iris? 2. Neurons that fi re in response to specifi c edges, lines, a. To focus light on the retina angles, and movements are called what? 1. c 2. d b. To process color a. Rods c. To allow light into the eye b. Cones d. To enable night vision c. Ganglion cells e. To detect specifi c shapes d. Feature detectors e. Bipolar cells

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3. Signal detection theory is most closely associated with 9. Which of the following best represents an absolute 3. c 7. b 11. d which perception process? threshold? a. Vision a. A guitar player knows that his D string has just gone 4. c 8. a 12. c b. Sensory adaptation out of tune. 5. c 9. d 13. c c. Absolute thresholds b. A photographer can tell that the natural light d. Smell available for a photograph has just faded slightly. 6. d 10. c e. Context effects c. Your friend amazes you by correctly identifying 4. Which of the following represents perceptual constancy? unlabeled glasses of Coke and Pepsi. d. A cook can just barely taste the salt she has added to a. We recognize the taste of McDonald’s food each time Rubric for Free-Response her soup. we eat it. e. Your mom throws out the milk because she says the Question 2 b. In photos of people, the people almost always are taste is “off.” perceived as fi gure and everything else as ground. 10. 1 point: Gate-control theory describes c. We know that the color of a printed page has not Which of the following describes a perception process changed as it moves from sunlight into shadow. that the Gestalt psychologists would have been how pain is experienced: Pain “gates” d. From the time they are very young, most people can interested in? open or close, determining which recognize the smell of a dentist’s offi ce. a. Depth perception and how it allows us to survive in e. The cold water in a lake doesn’t seem so cold after the world sensations might be perceived (or not you have been swimming in it for a few minutes. b. Why we see an object near us as closer rather than perceived) as pain. In this scenario, 5. Our tendency to see faces in clouds and other ambiguous larger Ester might experience pain when she stimuli is partly based on what perception principle? c. How an organized whole is formed out of its component pieces runs into the doorway due to gate- a. Selective attention d. What the smallest units of perception are b. ESP control theory. pp. 203–204 e. The similarities between shape constancy and size c. Perceptual set constancy d. Shape constancy 1 point: Ester’s vestibular sense was 11. e. Bottom-up processing Which perception process are the hammer, anvil, and involved as she stumbled and fell. Our stirrup involved in? 6. The process by which rods and cones change vestibular sense helps us maintain our electromagnetic energy into neural messages is called a. Processing intense colors what? b. Processing information related to our sense of balance. We receive balance informa- balance a. Adaptation tion from hair cells in our inner ear c. Supporting a structural frame to hold the eardrum b. Accommodation d. Transmitting sound waves to the cochlea about our orientation in space. c. Parallel processing e. Holding hair cells that enable hearing pp. 209–210 d. Transduction 12. e. Perceptual setting Which of the following might result from a disruption of your vestibular sense? 1 point: Selective attention determines 7. Which of the following is most likely to infl uence our memory of a painful event? a. Inability to detect the position of your arm without which sensations we will perceive looking at it a. The overall length of the event and attend to. In this situation, Ester’s b. Loss of the ability to detect bitter tastes b. The intensity of pain at the end of the event c. Dizziness and a loss of balance selective attention system switches c. The reason for the pain d. An inability to detect pain d. The amount of rest you’ve had in the 24 hours her attention to the shadowy fi gure, e. Loss of color vision preceding the event causing her to perceive it and act. After 13. When we go to the movies, we see smooth continuous e. The specifi c part of the body that experiences the Ester notices this fi gure, she focuses on pain motion rather than a series of still images because of which process? 8. Frequency theory relates to which element of the this situation, possibly not perceiving hearing process? a. The phi phenomenon many other sensations as she focuses b. Perceptual set a. Rate at which the basilar membrane vibrates on catching the mystery fi gure. c. Stroboscopic movement b. Number of fi bers in the auditory nerve d. Relative motion p. 152 c. Point at which the basilar membrane exhibits the e. Illusory effect most vibration 1 point: Signal detection theory d. Decibel level of a sound e. Number of hair cells in each cochlea predicts when we will perceive weak or faint sensations. In this scenario, Ester detected the weak signal of someone suddenly ducking into a doorway. p. 156 MyersAP_SE_2e_Mod21_B.indd 214 1/21/14 9:34 AM MyersAP_SE_2e_Mod21_B.indd 215 1/21/14 9:34 AM 1 point: Binocular cues are one of the principle ways we perceive depth and distance with both eyes. Something may have gone wrong with binocular cues for Ester in this situation because she misjudged the distance to the doorway and ran into it. p. 184 1 point: Perceptual set is a mental expectation or assumption about how we should perceive a set of sensations. In this scenario, Ester had a powerful perceptual set for her roommate, immediately recognizing her in the end. p. 163

Review Unit IV 215

MyersPsyAP_TE_2e_U04.indd 215 2/20/14 8:12 AM 216 Unit IV Sensation and Perception

Answers to Multiple-Choice 14. Two monocular depth cues are most responsible for 15. Which of the following phrases accurately describes top- our ability to know that a jet fl ying overhead is at an down processing? Questions elevation of several miles. One cue is relative size. What a. The entry-level data captured by our various sensory is the other? systems 14. a 15. b a. Relative motion b. The effect that our experiences and expectations have b. Retinal disparity on perception c. Interposition c. Our tendency to scan a visual fi eld from top to d. Light and shadow bottom Rubric for Free-Response e. Linear perspective d. Our inclination to follow a predetermined set of steps Question 3 to process sound (Note: Students should include the e. The fact that information is processed by the higher regions of the brain before it reaches the lower brain terms in some logical “beginning to end” order, which will likely be diff erent from the order in which the points Free-Response Questions are listed below.) 1. While listening to the orchestra as she dances the lead 2. Ester is walking to her chemistry class when she notices role in Swan Lake, a ballerina concludes her performance someone in the distance suddenly duck into a dark 1 point: Transduction occurs when with a pirouette, spinning around several times before doorway. She is suspicious and starts to chase the leaping into the arms of her dance partner. fi gure, but misjudges the distance and accidentally runs light energy is transformed into neural Discuss how the ballerina relied on the following and into the door. She falls down but quickly recovers, and signals in the eye (specifi cally, in the how each is important. laughs when she discovers that the mystery person is her roommate, who was avoiding Ester, because she had retina). In this situation, light refl ected • Kinesthetic sense borrowed Ester’s favorite sweater without permission off the page (or screen) enters the eye • Vestibular sense and was afraid Ester might be angry. and is changed into neural signals. • Semicircular canals Use the following terms to explain the perceptual p. 155 • Hearing processes involved in this scenario. Rubric for Free Response Question 1 • Gate-control theory 1 point: Top-down processing occurs • Vestibular sense 1 point: Kinesthesia will allow the ballerina to sense the as we read this text. We use our expec- position of different parts of her body as she dances the role. • Selective attention tations and prior experience (spe- Thus, she will know that she is to start by facing the audience • Signal detection theory cifi cally, the shapes of letters and our and, although she has spun around several times, she will • Binocular cues always be aware of where the audience is, and where to put • Perceptual set knowledge of words) to read the text her feet and arms in order to accomplish the choreography. (6 points) and make meaning. p. 152 Page 209 1 point: The vestibular sense enables the dancer to sense her 3. Describe, from the beginning of the process to the end, 1 point: Light bounces off the page or body position and to maintain her balance. Pages 209–210 how your brain is perceiving the words you are reading screen and enters the eye. This image 1 point: Semicircular canals near her inner ear help the right now. Use the following terms in your answer. ballerina maintain her sense of balance. She needs this • Transduction is projected on the retina in the back balance as she leaps and spins, and her training allows her • Top-down processing of the eye. Neurons in the retina fi re in to use her vestibular sense to maintain balance rather than • Retina response to stimulation from this light, become dizzy. Pages 195 and 209 1 point: The ballerina’s sense of hearing allows her to • Pupil starting the process of transduction. perceive the music and to dance to the correct rhythm of • Occipital lobe p. 172 each piece of music. Pages 194–199 • Rods • Feature detectors 1 point: The image of the text enters (7 points) the eye through the pupil, a hole in the front of the eye. p. 172 Multiple-choice self-tests and more may be found at www.worthpublishers.com/MyersAP2e 1 point: Neural messages from the optic nerve end up in the occipital lobe, where the brain makes sense of the image (using feature detectors). Visual perception occurs in the occipi- 1MyersAP_SE_2e_Mod21_B.indd point: Feature detectors 216 are specialized 1/23/14 1:58 PM tal lobe. pp. 174–175 groups of neurons in the occipital lobe that fi re in response to specifi c visual features, such 1 point: Rods are specialized neurons as curves, angles, or shapes. Feature detectors in the retina that fi re in response to in our occipital lobes fi re in response to the black and white images (such as black curves and shapes of letters, beginning the text against a white background on a perception process that ends with our percep- page or screen). p. 173 tion of words on the page or screen. p. 175

216 Unit IV Sensation and Perception

MyersPsyAP_TE_2e_U04.indd 216 2/20/14 8:12 AM