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Excellent notes for PSYB51H3 Lecture 4: Perceiving and recognizing objects

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University of Toronto Scarborough
Matthias Neimier

Lecture 4: Perceiving and recognizing objects BOTH VISUAL FIELDS PROJECTED INT BOTH EYES for most of visual field both eyes see same thing only eye in periphery looks different lens in pupil everything is inverted right and left eye respectively ganglion cells send axons through optic chiasm actions of ganglion cells travel always part of retina crossover nasal parts - right eye left visual field and vice versa LGN - next relay station where ganglion cells form retna synapse to ganglion cells v1 - striate area - vertical area different structures What is heteronymous hemianopia? Please describe the symptoms. Which brain structure is likely damage? What is the contrast sensitivity function? Can you sketch what it usually looks like? What does that reflect in terms of perception? Answer: heteronymois - 2 eyes have hemi blindness for visual field due to lesions in optic chiasm right eye is blind for the right visual field and left eye is blind for the left visual field more to do with tumors grow somewhere nearby curve graph - horizontal axis - spatial freq. (cpd) vertical axis - sensitivity (contrast) - luminance - white strong luminous contrast middle darker gray - smaller contrast higher the sensitivity inverted U shape - interpretation : Curve indicated that at certain range of 60cpd at some pt. not resolve spatial freq. anymore - no sensitivity at all - 0 if low(minimum) no freq. if middle - maximum then higher sensitivity designed to sensitivity to frequency recognize it as house = Perception different but identify object as same house Optic perception - process that pcs. Things together simple elements into cohesive 3d structure that resolves perceive a house as entity Object recog. - have you ever seen as house? no experience assoc. what you’ve seen to what you’ve seen before - recognize - memory functions memory work together to perform recognition entered other house object identification Object naming - language function - in english call it a house in other language call it different dark in one side bright in one side what can a pc percieve bitmap for pixel knows how bright is a pixel - write computer algorithm find pixels with diff. luminance strong diff. give pixel high value calculating contrast like retina do you only have individual dots - one higher than other contrast individual dots in continues lines in next steps individual dots for each line problem: you have gaps and have to do with original image - difference in contrast not very strong luminance of background similarly the same find dots of pts. not leave gaps. if gaps - need to work on it correct orientation sensitivity have same recptor field with diff. orientation sensitivities 1 neuron with type of sensitivity what do we do with edges and curves - tip of room have discontinuity -we could invent type of neuron in visual sys. that is good in detect these changes but same neurons can detect it also - not mean edge is meaningful type of neuron will fail at that pt. we could finf neurons that actually different to little gap - receptor field loud of neuron - accept continues line though it's not respons too if gap is meaningful - discontinoies line that you dont want to continue cannot work - struturalism fails pc together a little things that gives rise to perception in complex things - not tell diff. of incomplete object and diff. types of object - Structuralism fails bec, of this if onfo. from retina to see something what else can we use? Use certain rules - systematic effects to world that see certain things and extract things from that Gestalt Gestalt school move to U.S. big impact in behaviorism or dark age of psychology PAlm and rock pick up gestalt and work more in that cannot pc. indiidual elements and tha't all grouping laws set of rules that describe elements of image on how they will group together. Page 12: which line tend to group together to be same part of line 2 lines that continue in highest degree of smoothness see together not smooth need more info. Neuron number 1 : is responsive to this line bec same visual field and has orientation sensitivity neurons talk to each other - 10,000 connections to each other - neurons talk to each other encourage each other and have good connection - enhance activity - Red and orange not like too much 3 and that neuron inhibits them 1 is wired to positive connection with other neurons -in receptive fields of same orientation sensitivity then enhance -but if diff. orientation will enhance gestalt neurons will respond equally to lines - loop more salient fire continuously and see it as a whole. Page 13: smooth contours - why some smooth and some are not. 2 lines - not entirely sure if one is a continues line - contour not be smooth Gestalt of good contiuation - oowerful if we see this as one line parallel to each other - smooth and belong together curve v - one linebut includes other gestalt element - different color so add more not see things as continuous then find smoothness Page 14: contours to identify smoothness stuffs really belong together - do have a certain degree of smoothness perceive smoothness actually in real world world is not random and have smoothness on it Filling gaps of house - see some lines actually but not have illusion contours fill in gaps focus contours if not - feel that ear continuous join together in pt when line stop same smooth line - cant se as half circle or circular visual system likely rule out coincidence things seen more likely than others seen together V1 produce illsuory contours but not enough bunch of patterns - pentagon top right pacmans but not see in there -form illusory contour or not voltage diff. from scalp project in back - positivity in are evolving here difference - lateral occip. complex - brain lesion there see colors and textures but not see obj. anymore -diff. peak 150 ms earliest response C1 component that originates form V1 and is diff. to measure info. forwarded to high level and feed back help perceive objects in gestalt page 17: graph A - lines and 2 squares - pcs together with elements group things together proximity - group together with distance not work well in b. graph - diamonds in left red and right green - 2 squares - but 2 types of features group together - shape and color gestaly law not work across dimensions top left Page 18: grouping prnciples - line 1 and 2 not group bec. 2 and 3 run parallel - same tracts have in common symmetry cue that they belong together not coincidence e.g. lamp: lamp now difficult to see - not there but it's on of corner - lamp less visual sys. say it's fading - move together belong together (belong in the same object Synchr
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