Sensation and perception_2012Presentation Transcript
Sensation and Perception
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.
Perceptual InterpretationPerceptual Interpretation Perceptual Adaptation Perceptual Set Perception and Human Factors
From Sensation to RecognitionTim Bieber/ The Image Bank
Information Processing in the Visual Cortex• Early 1960s: Hubel and Wiesel – Microelectrode recording of axons in primary visual cortex of animals – Discovered feature detectors: neurons that respond selectively to lines, edges, etc. – Groundbreaking research: Nobel Prize in 1981• Later research: cells specific to faces in the temporal lobes of monkeys and humans
Shape Detection Specific combinations of temporal lobe activity occur as people look at shoes, faces, chairs and houses.Ishai, Ungerleider, Martin and Haxby/ NIMH
Visual Information Processing Processing of several aspects of the stimulussimultaneously is called parallel processing. The braindivides a visual scene into subdivisions such as color, depth, form and movement etc.
Color Constancy Color of an object remains the same under differentilluminations. However, when context changes color of an object may look different. R. Beau Lotto at University College, London
Figure 4.17 Bottom-up versus top-down processing
Perception in Brain Our perceptions are a combination of sensory(bottom-up) and cognitive (top-down) processes.
Bottom-up ProcessingAnalysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind.Letter “A” is sensed as a black blotch decomposed into features by the brain and perceived as an “A” by our mind .
Figure 4.23 Context effects
Principles of Perception• Gestalt principles of form perception: – figure-ground, proximity, closure, similarity, simplicity, and continuity• Recent research: – Perceptual hypotheses • Context
Figure 4.18 The principle of figure and ground
Figure 4.21 A famous reversible figure
Figure 4.19 Gestalt principles of perceptual organization
Making Sense of ComplexityOur sensory and perceptual processes work together to help us sort out complex images. “The Forest Has Eyes,” Bev Doolittle
Figure 4.20 Perceptual hypotheses
Figure 4.22 The Necker cube
The Power of Misleading Cues: Visual Illusions• Optical Illusions - discrepancy between visual appearance and physical reality• Famous optical illusions: Muller-Lyer Illusion, Ponzo Illusion, Poggendorf Illusion, Upside-Down T Illusion, Zollner Illusion, the Ames Room, and Impossible Figures• Cultural differences: Perceptual hypotheses at work
• Imagine that you are outside on a clear night in which there are no clouds, and there is a bright full Moon. Pretend that on a table in front of you are objects that range in size from a BB to a beach ball as follows: 1. BB 8. Baseball 2. Pea 9. Softball 3. Dime 10. Small salad plate 11. Large dinner plate 4. Penny 12. Frisbee 5. Nickel 13. Basketball 6. Quarter 14. Beach ball 7. Golf ballPlease pretend that you are going to pick one of these things thatWHEN HELD AT ARM’S LENGTH JUST COVERS UP THE MOON.Imagine that you are picking one that when you hold it in your handwill JUST BARELY COVER UP THE MOON so that you can nolonger see it.
Window Mac O X http://www.youtube.com/watch?v=5ic7QGjGEX8
Selective Attention• Neisser’s SA Test – http://www.youtube.com/watch?v=JX2BJC12uXQ – http://www.youtube.com/watch?v=Ahg6qcgoay4&
Aoccdrnig to a rscheearch at Cmabrigde Uinervtisy,• it deosnt mttaer in waht oredr the ltteers in a wrod are, the olny iprmoetnt tihng is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a toatl mses and you can sitll raed it wouthit porbelm. Tihs is bcuseae the huamn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe.
But does it matter?• 1) A vheclie epxledod at a plocie cehckipont near the UN haduqertares in Bagahdd on Mnoday kilinlg the bmober and an Irqai polcie offceir• 2) Big ccunoil tax ineesacrs tihs yaer hvae seezueqd the inmcoes of mnay pneosenirs• 3) A dootcr has aimttded the magltheuansr of a tageene ceacnr pintaet who deid aetfr a hatospil durg blendur
the rset can be a toatl mses and you can sitll raed it wouthit porbelm…• Short words are easy• Function words (the, be, and, you etc.) stay the same - mostly because they are short words• Of the 15 words in this sentence, there are 8 that are still in the correct order.• Transpositions of adjacent letters (e.g. porbelm for problem) are easier to read than more distant transpositions (e.g. pborlem).• None of the words that have reordered letters create another word (wouthit vs witohut).• Transpositions were used that preseve the sound of the original word (e.g. toatl vs ttaol for total).• The text is reasonably predictable.
Tihs is bcuseae the huamn mnid deos not raed ervey lteter byistlef, but the wrod as a wlohe...• people do not ordinarily read each letter in a word individually• information in the shape of an entire word plays an important role in reading. For instance, "CaSe MiXiNg" substantially slows down reading
Trehe wlil be a qiuz onpotiercepn at the end of cslas toady
Perceptual SetA mental predisposition to perceive one thing andnot another. What you see in the center picture is influenced by flanking pictures. From Shepard, 1990.
Schemas Schemas are concepts that organize and interpret unfamiliar information. Courtesy of Anna Elizabeth VoskuilChildrens schemas represent reality as well as their abilities to represent what they see.
Eye & MouthEyes and mouth play a dominant role in face recognition. Courtesy of Christopher Tyler
Perception & Human Factors Human factors psychologists design machines that assist our natural perceptions. Courtesy of General ElectricPhotodisc/ Punchstock The knobs for the stove burners on the right is easier to understand than one on the left.
Claims of ESP Telepathy: Mind-to mind communication. One person sending thoughts and the other receiving it. Clairvoyance: Perception of remote events. Like sensing a friend’s house on fire. Precognition: Perceiving future events. Such as a political leader’s death.
Premonitions or Pretensions?Can psychics see the future? Can psychics aid police in identifying locations of dead bodies? What about psychic predictions of the famous Nostradamus?The answers to these questions are NO! Nostradamus’ predictions are “retrofitted” to events that took place afterwards.
Anagrams• LULB• CALEM• NUKKS• SEUMO• BAZER
Anagrams• NORC• NOONI• MATOOT• PREPPE• TEBE
Fig. 4.14, p. 109
Fig. 4.15, p. 109
Perception RevisitedIs perception innate or acquired?