Unit 3 - Sensation & Perception
Chapter 4 Part 1: Intro. to S & P Today’s Goals ●Can you: ○Define sensation and perception ○Discuss basic principles of sensory transduction, including absolute threshold, difference threshold, signal detection, and sensory adaptation. ○Explain the role of top-down processing in producing vulnerability to illusion. Sensation & Perception
How do we construct our representations of the external world?
To represent the world, we must detect physical energy (stimulus) from the environment and convert it into neural signals, a process called sensation.
When we select, organize, and interpret our sensations, the process is called perception. What do you sense? In this case, what do you see?
What do you perceive? Bottom-up Processing
Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind.
Which of the following is the American flag?
Knowing that the bottom middle flag is the American flag is due to bottom-up processing…your senses break down the flags into colors, shapes and lines…which you then process and organize to figure out which is the American flag. Top-Down Processing
Information processing guided by higher-level mental processes as we construct perceptions drawing on our experience and expectations.
Y-u c-n r-ad -hi- se-te-ce -it- ev-ry -hi-d l-tt-r m-ss-ng.
The reason you can…is top-down processing! Your expectations and experiences let you fill in the blanks by making inferences on what you think “should” be there! Making Sense of Complexity Bottom-up and top-down processing work together to help us sort out complex images.
“The Forest Has Eyes,” Bev Doolittle
Thresholds Absolute Threshold: Minimum stimulation needed to detect a particular stimulus 50% of the time.
Difference Threshold: Minimum difference between two stimuli required for detection 50% of the time, also called just noticeable difference (JND). Weber’s Law
The size of the JND is proportional to the intensity of the stimulus ●if the stimulus intensity is high, the JND will be large (or it will take a bigger increase to notice the difference)
●if the stimulus intensity is low, the JND will be smaller (or it will take less of an increase to notice the difference)
Subliminal Threshold
When stimuli are below one’s absolute threshold for conscious awareness. In other words…for most people these items are not consciously detected.
HOWEVER…it is possible that some will notice these items! Examples of “subliminal” messages in advertisements…
In the spring/summer of 1990, Pepsi distributed a line of “Cool Cans” as part of a promotional campaign. All 4 of them are shown below…
…the 2nd “NEON” can apparently had an “embedded” message if you stacked two cans together.. http://www.snopes.com/business/hidden/coolcans.as p An embedded “subliminal” message was found in 2004 on the french translation portion of a care http://www.tombihn.com / tag on Tom Bihn backpacks/laptop cases/briefcases…
What does it say???? “We’re sorry our president is an idiot. We didn’t vote for him.” Many people viewed this as a slam against President Bush…the company maintains that it is a joke between a Info from…http://www.snopes.com/business/hidden/tombihn.asp seamstress and the CEO. Bush campaign ad controversy…
During the 2000 Presidential campaign…the following ad was run nationally on TV by the Republican party…
The Democratic party claimed that the Republicans were trying to use “subliminal” messages to influence the national public…so they asked the FCC to investigate the TV ad!
The ad's creator calls the word's appearance a "visual drumbeat" meant to grab viewers' attention and not an intentional message. It was supposed to be an abbreviated version of “bureaucrats”… Bush also said “rats” ad not meant to be a subliminal message Subliminal Messages…Backmasking? It is recording technique in which a sound or message is recorded backward onto a track that is meant to be played forward.
This is a deliberate process…currently the technique is being used to censor words or phrases for "clean" releases of songs.
Backmasking was popularized by The Beatles, who used backward vocals and instrumentation on their 1966 album Revolver.
The Backmasking has been a controversial topic in the US since the 1980s, when allegations from Christian groups of its use for Satanic purposes were made against prominent rock musicians, leading to record-burning protests and proposed anti-backmasking legislation by state and federal governments.
Whether backmasked messages exist is a debate, as is whether backmasking can be used subliminally to affect listeners. Subliminal Messages…Reverse Speech? Background… ●initially gained worldwide fame in the early 80s as “backmasking” in music ●the pioneer of this field is Australian, David John Oates
What is reverse speech? ●idea that if human speech is recorded and played backwards, mixed amongst the gibberish at regular intervals can be heard very clear statements ●statements are usually short and relate to the content of the forward speech ●believed to be a natural part of our speech processes ●Oates believes that the reverse speech is our unconscious mind finding a “voice” ○for example…if telling a lie in forward speech, in reverse the truth may come out Some examples of reverse speech…. You will hear the “forward” message 1st…followed by 3 “reverse” messages (1 at regular speed and 2 at slowed speeds). Can you figure out what is being said???
“I surely would fit in” “See the dream” “Soon I’ll beat the law”
For more examples visit…http://www.reversespeech.com/home.htm
Do the previous items really constitute subliminal messages?
Do subliminal messages really influence our behaviors?
Studies have found that subliminal words flashed briefly on a screen can “prime” a person’s later responses…but will not impact a large group’s buying habits! Signal Detection Theory (SDT)
Predicts how and when we detect the presence of a faint stimulus (signal) amid background noise (other stimulation). Assumes that there is no single absolute threshold and detection depends on: JOE!
●Person’s experience ●Expectations ●Motivation ●Level of fatigue Signal Detection Theory (SDT)
Presence of Stimulus
Yes No
No
Yes Detection of StimulusofDetection Sensory Adaptation Diminished sensitivity as a consequence of constant stimulation.
Put a band aid on your arm and After you initially get into a pool, after a while you don’t sense it. it no longer feels cold.
Let’s test the idea of sensory adaptation… Sensory Adaptation – Marker Test
Number your paper to 12… Each time I tell you to “SMELL”, please quickly sniff your marker and quickly rate the INTENSITY OF THE AROMA on a scale of 1 – 20 (1 = very slight smell 20 = very strong smell) Quickly switch markers with your neighbor and rate the intensity of the aroma of their marker… What happened over the various trials?