Asgn2q-sProblem: How can you get such good information about distal objectfrom proximal stimulusProximal stimulusDistal stimulus or objectPerception is distal objectcentered:- rapid; automatic;unconscious- stable, despite proximalstimulus variation: perceptual constancyPerceptual development: Nurture (environment): empiricism; Nature (genetics, development), nativismEvidence for Nurture: Deprivation, distortion during development –> deficitsHuman case studies- born blind; regain sight –> defective perception - active movement requiredAnimal experimental studies: Raise in restricted environment- No stimulation -> severe deficit- Limited normal experience –> normal perception- active movement requiredPeople can adapt to effects of distorting goggles- active movement requiredEvidence for Nature:- brain has basic connections built in to visual system at birth- test by studying perceptual abilities of the very young: - natural reactions like lookingVisual cliffLooming stimuliNature & Nurture work together:Brain organization thru development is under interactive genetic and environmental control- species diff; individual diff.Brain development depends on physical & sensory environment: brain plasticity- redirect visual input to auditory cortex:- auditory cortex becomes visual- sensory stimulation required for normal development- changes in adult brain due to stimulation- musician - non-musician brain differenceForm perceptionGestalt theory: perception relation between parts- phi phenomenon (left)- relative motion (right)Lateral Inhibition:Figures (objects) against groundContour (boundary) separates figure from groundIllusory boundaries Gestalt “laws” of grouping- proximity- similarity- good continuation- closure- good form- common fateFeature detection model:- Unique pattern of activity represents object- activation of detectors sensitive to features thatmake up the objectGeons: Basic shapesCombine to form objects:Hierarchy of processing- increasingly complex adequate stimuli:Neurons’ adequate stimuli get more selective- combine info. from less selective neuron from lowerlevelsHubel & Wiesel model: simple, complex, hyper-complexcells, “feature cells” at progressively higher levels in visual cortexEach higher level responds only to combination of simpler features from lower levelsAt highest levels: neurons respond only to complex combinations of features like objects, faces, handsEach higher level responds only to combination of simpler features from lower levelsInterconnected parallel pathways for color, pattern, movementMotion and object perceptionhttp://www.leffingwell.com/chirality/alphaionone.htmhttp://WWW.PSY.VANDERBILT.EDU/faculty/blake/DepthCapture/DepthCapture.htmlEffects of brain damage:- primary cortex: conscious blindness- temporal (“lower”) association cortex: agnosia (can’t recognize)- parietal (“upper”) association cortex: perception of ; moving objects