PERCEPTIONWhy?What is an illusion?How do we perceive depth?Psyc 100 1st Edition Lecture 10Outline of Last Lecture I. ExamOutline of current LectureI. SensationII. PerceptionCurrent LectureExperiencing events: 2 StagesStage 1:SENSATIONThe processes of:-Converting the physical world into a mental representation (transduction)-And relaying that information to the brain (conduction)TransductionEX:  Variation of light -> experience of color Variations of air pressure -> experience of soundStage 2:PERCEPTIONThe processes of: selection, organization and interpretation EX:  We can recognize the color green We can distinguish Bach from Britney SpearsThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.PERCEPTION Def: The process by which we  select,  organize, and  interpret these mental representations EX: - We can recognize the color red- We can distinguish Bach from Britney SpearsORGANIZATION & INTERPRETATIONMost Important Point of the day: There is not a 1:1 correspondence between our perceptual representation of the world and the physical reality of the world.Why?  Because physical information is ambiguous. Ex: Seeing your roommate across the pondEx. “What’s the matter, honey?” “Nothing”  We do this with all sorts of physical world information-We take the available info and interpret it based on what we know about our worldPerceptual IllusionsWhat is an illusion?-Case where the rules that we use to interpret the world, which are usually true, are not true and lead us to mis-interpretationExamples of Visual Illusions:1) Vertical vs. Horizontal lines-We tend to think that horizontal lines are shorter than the vertical lines2) Context effects-An L in a handwritten note looks like a D in another word but is not read as such3) Experience effects the world: Muller-Lyer : <-> >-< Lines look different because of environment we grow up in (people who have grown up in a house with right angles vs people who have grown up in a round hut)Why so many visual illusions??? Visual capture – Vision dominates Ex: Stare at phone when listening to voicemailRULES: GESTALT PSYCHOLOGYGestalt psychology – Tried to specify the rules of perception for how we distinguish coherent, separate objects German word for ‘form’ or ‘whole’We work hard to perceive coherence in our environment We try to see the world as composed of discrete, separate objects We perceive certain elemental forms and combine them together to create complex whole scenesRule 1:Figure- ground:  Perceive object as distinct from its surroundingsRules of grouping:1. Proximity  Group nearby objects together2. Similarity  Group figures that are similar3. Continuity Perceive continuous patterns4. Connectedness Spots, lines and areas are seen as unit when connectedo (3&4) We opt for most simplistic interpretation (books calls simplicity)Note: book combines 3 & 4 and calls “simplicity”5. Closure  Fill in gapsPoint:Sometimes local features assist with the perception of global featuresBUTSometimes global features assist with local featuresConstancy /Perceptual SetPerceptual Constancy: We are able to perceive an object as unchanging even though the stimuli we receive from it change. Once we lock onto a particular interpretation of a stimulus, we tend to stick with that perceptionTypes of constancy:1) Size Constancy – Position causes illusion that height or size has changed2) Shape Constancy – Orientation of object creates illusion that object has changed shapeWhen constancy rules fail us (Exceptions):- Neckar Cube – Cube leaning forward seeing top, cube leaning backward seeing bottom - Patterns with multiple interpretations – Seeing a rabbit and a duck per orientationPerceptual set: Expectations are a big determinant of how we perceive a scene To believe is to seeEX: 1. Stereotypes – Babies moving arms around when laying down (girl will be cheerleader and boy will be boxer)2. Coast example – Coast, coast, coast, coast. What do you put into a toaster? A: Bread3. AnagramsDEPTH PERCEPTIONHow do we perceive depth? Two main sources of information:1. Binocular cues: Rely on the fact that we have two eyes Each eye produces a slightly different image because the eyes are in different locations These cues are ones in which our brains imposes structure on the environment – Gestalt rules2. Monocular cues Can be perceived with one eye only These cues are ones in which brain makes use of info that exists in the environement.Binocular cuesBinocular cues  Brain informs/provides structure for our perception Averages the two images from our two eyesExamples: 1) Retinal Disparity –  Images from the two eyes differ The larger the difference (disparity) between two images the retinas receive, the closer the object is to our eyes.Ex. Finger sausageHand telescope Play catch with one eye closed2) Convergence –  The closer something is, the larger the angle forms by the two eyes Two eyes move inward for near