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Exam 1 • Top Score: 50 • Mean: 43.4 • Median: 44.5 • Mode: 44 • SD: 5.11 Sensation & Perception • Problems: – Start time screwed up for both; got resolved within 15 minutes – Duplicate question (my fault) – Wrong answers for 3rd graph question (changed within 15 minutes, only Chapter 6 affected 5 students; their scores have been corrected) • HELP LINE: 1-800-936-6899 Psy 12000.003 • Suggestions: – No go back? 1 – Others? 2 Announcement Sensation & Perception How do we construct our representations of the external • Participants Needed world? – $10 to participate in experiment. • To represent the world, we must first detect – You (ask a friend, too) physical energy (a stimulus) from the environment and convert it into neural • Contact: Eric Wesselmann signals. This is a process called sensation. – [email protected] • Wilhelm Wundt: “Father of Experimental Psychology” – Introspectionism When we select, organize, and interpret our sensations, the process is called perception. 3 4 The Dark Restaurant The Senses “I went to this restaurant in Berlin…” • Traditional Five: – Sight – Hearing – Touch – Smell • http://www.unsicht-bar.com/unsicht-bar- – Taste berlin-v2/en/html/home_1_idea.html • Six others that humans have – Nociception (pain) – Equilbrioception (balance) – Proprioception & Kinesthesia (joint motion and acceleration) – Sense of time – Thermoception (temperature) – Magnetoception (direction) 5 6 1 Bottom-up Processing Top-Down Processing Analysis of the stimulus begins with the sense receptors Information processing guided by higher-level and works up to the level of the brain and mind. mental processes as we construct perceptions, drawing on our experience and expectations. Letter “A” is really a black blotch broken down into features THE CHT by the brain that we perceive as an “A.” 7 8 Top-Down or Bottom-Up? Making Sense of Complexity Our sensory and perceptual processes work together to help us sort out complex images. Learned depth cues make this a 9 10 top down perceptual distortion “The Forest Has Eyes,” Bev Doolittle Sensing the World Exploring the Senses Senses suit an organism’s needs, . What stimuli cross our threshold for conscious enabling survival. awareness? A frog feeds on flying insects so visual . Could we be influenced by stimuli too weak acuity must be very sensitive; (subliminal) to be perceived? a male silkworm moth is sensitive to female sex-attractant odor; and we as human beings are sensitive to . Why are we unaware of unchanging stimuli, like a sound frequencies that represent the band-aid on our skin? range of human voice. 11 12 2 Psychophysics 22nd October 1850 A study of the relationship between physical characteristics of stimuli and our psychological A relative increase in experience with them. mental intensity, Fechner Psychological realized, might be Physical World World measured in terms of the Light Brightness relative increase in physical energy required Sound Volume to bring it about. Pressure Weight Gustav Fechner (1801-1887) Sugar Sweet 13 14 Detection Thresholds Absolute Threshold: Minimum stimulation needed for Absolute an individual to detect a particular stimulus 50% of the Threshold time. Intensity No No No Yes Yes Observer’s Response Detected Proportion of “Yes” Responses of “Yes” Proportion 0.00 0.50 1.00 Tell when you (the observer) detect the light. 15 0 5 10 15 20 25 16 Stimulus Intensity (lumens) Subliminal Threshold Difference Threshold Subliminal Threshold: When Difference Threshold: Minimum difference between two stimuli are below one’s stimuli required for detection 50% of the time, also called absolute threshold for just noticeable difference (JND). conscious awareness. Difference Threshold Kurt Scholz/ Superstock No No Yes Observer’s Response 17 Tell when you (observer) detect a difference in the light. 18 3 Weber’s Law Signal Detection Theory (SDT) Two stimuli must differ by a constant minimum Predicts how and when we detect the presence of a percentage (rather than a constant amount), to be faint stimulus (signal) amid background noise (other perceived as different. Weber fraction: k = δI/I. stimulation). SDT assumes that there is no single absolute threshold and detection depends on: Stimulus Constant (k) Light 8% Person’s experience Stone Images Tony Carol Lee/ Weight 2% Expectations Motivation Tone 3% Level of fatigue 19 20 SDT Matrix Sensory Adaptation The observer decides whether she hears the tone or not, Diminished sensitivity as a consequence of constant based on the signal being present or not. This translates stimulation. into four outcomes. Decision Yes No Present Hit Miss Signal False Correct Absent Put a band aid on your arm and after awhile Alarm Rejection you don’t sense it. 21 22 Now you see, now you don’t Sensation without Perception Video on Visual Prosopagnosia 23 24 4 Sense of Touch Skin Senses The sense of touch is a mix of four distinct skin senses Only pressure has identifiable receptors. All other skin —pressure, cold, warmth, and pain. sensations are variations of pressure, warmth, cold and pain. Pressure Vibration Vibration Bruce Ayers/ Stone/ Getty Images Stone/ Getty Images Ayers/ Bruce 25 Burning hot Cold, warmth and pain 26 Touch Sensation/Perception Taste • The intense tickling Traditionally, taste sensations consisted of sweet, salty, sensation that makes sour, and bitter tastes. Recently, receptors for a fifth you laugh taste have been discovered called “Umami”. uncontrollably… – Only happens when someone else tickles you – You cannot tickle yourself and get this response (Blakemore, et al., Sweet Sour Salty Bitter Umami 2000) (Fresh • Why? Chicken) 27 28 Sensory Interaction When one sense affects another sense, sensory interaction takes place. So, the taste of strawberry interacts with its smell and its texture on the tongue to produce flavor. Taste Scientific American Frontiers: Tasters and Super-tasters 29 30 5 Smell Age, Gender, and Smell Like taste, smell is a chemical sense. Odorants enter the Ability to identify smell peaks during early adulthood, nasal cavity to stimulate 5 million receptors to sense but steadily declines after that. Women are better at smell. Unlike taste, there are many different forms of detecting odors than men. smell. 31 32 Example of Sensory Interaction Smell and Memories Audition/Vision The brain region for smell Count the Fs: (in red) is closely connected with the brain FINISHED FILES ARE THE RESULTS regions involved with OF YEARS OF SCIENTIFIC STUDY memory (limbic system). COMBINED WITH THE EXPERIENCE That is why strong memories are made OF YEARS. through the sense of smell. 33 34 Pheromones, Odor, and Sweaty T-Shirts • http://www.pbs.org/wgbh/evolution/library/ 01/6/l_016_08.html • Adaptive to prefer mate with different Vision immune system to one’s own: MHC (major histocompatibility locus) • Women preferred the scents of T-shirts worn by men whose MHC genes were different from their own. 35 36 6 Transduction The Stimulus Input: Light Energy In sensation, the transformation of stimulus energy into neural impulses. Phototransduction: Conversion of light energy into neural impulses that the brain can understand. Visible Spectrum Both Photos: Thomas Eisner Thomas Both Photos: 37 38 Light Characteristics Wavelength (Hue) Hue (color) is the dimension of color . Wavelength (hue/color) determined by the wavelength of the . Intensity (brightness) light. Saturation (purity) Wavelength is the distance from the peak of one wave to the peak of the next. 39 40 Wavelength (Hue) Intensity (Brightness) Intensity Amount of Violet Indigo Blue Green Yellow Orange Red energy in a wave determined by the amplitude. It 400 nm 700 nm is related to Short wavelengths Long wavelengths perceived brightness. Different wavelengths of light result in different colors. 41 42 7 Intensity (Brightness) Purity (Saturation) Saturated Saturated Blue color with varying levels of intensity. Monochromatic light added to green and red As intensity increases or decreases, blue color makes them less saturated. looks more “washed out” or “darkened.” 43 44 Color Solid The Eye Represents all three characteristics of light stimulus on this model. http://www.visionconnection.org 45 46 Parts of the eye The Lens Lens: Transparent 1. Cornea: Transparent tissue where light enters the structure behind the pupil eye. that changes shape to focus 2. Iris: Muscle that expands and contracts to change images on the retina. the size of the opening (pupil) for light. 3. Lens: Focuses the light rays on the retina. Accommodation: The 4. Retina: Contains sensory receptors that process process by which the eye’s visual information and sends it to the brain. lens changes shape to help focus near or far objects on the retina. 47 48 8 The Lens Retina Nearsightedness: A Retina: The light- condition in which sensitive inner nearby objects are seen surface of the eye, more clearly than distant containing receptor objects. rods and cones in addition to layers of Farsightedness: A other neurons condition in which (bipolar, ganglion faraway objects are seen cells) that process more clearly than near visual information. objects. 49 50 Optic Nerve, Blind Spot & Fovea Test your Blind Spot Optic nerve: Carries neural impulses from the eye to the brain. Use your textbook. Close your left eye, and fixate your Blind Spot: Point where the optic nerve leaves the eye because right eye on the black dot. Move the page towards your there are no receptor cells located there. This creates a blind spot. Fovea: Central point in the retina around which the eye’s eye and away from your eye. At some point the car on cones cluster. the right will disappear due to a blind spot. http://www.bergen.org 51 52 Photoreceptors Bipolar & Ganglion Cells Bipolar cells receive messages from photoreceptors and transmit them to ganglion cells, which are for the optic nerve. E.R. Lewis, Y.Y. Zeevi, F.S Werblin, 1969 53 54 9 Visual Information Processing Ganglion & Thalamic Cells Optic nerves connect to the thalamus in the middle of Retinal ganglion cells and thalamic neurons break the brain, and the thalamus connects to the visual down visual stimuli into small components and have cortex.
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