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PSY280H1 (40)
Chapter 5

chap 5 textbook notes

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Kristie Dukewich

CH5 – PERCEIVING OBJECTS AND SCENES Why Is It So Difficult To Design a Perceiving Machine?  THE GESTALT LAWS OF PERCEPTUAL ORGANIZATION – number of  INVERSE PROJECT PROBLEM – particular image on retina can be created principles proposed by Gestalt Psychologists who reject idea perception by different objects built up of sensations o Info. from single view point of object = ambiguous o PERCEPTUAL ORGANIZATION – grouping of elements in an image to  Cause stimulus on receptors to be ambiguous create larger object, explained by 6 laws of organization o Explanation: if object’s shape, distance, orientation known  can o LAW OF PRAGNANZ – every stimulus pattern is seen in such a way determine object’s shape on retina that the resulting structure is as simple as possible  But same image on retina can be create by infinite combine of  central law of Gestalt psychology those 3 features  AKA law of good figure/simplicity o Ex. Piece of paper viewed by retina  Ex. see 5 circles (a), not combination of 9 shapes (b)  Straight on  regular page = rectangular image on retina  Emulatable by slanted trapezoid/tilt rectangle o LAW OF SIMILARITY – similar things appear to be group together  Grouping based on similarity of shape, size or orientation  May occur for auditory stimuli  Ex. High pitch notes following each other form melody  Ex. See grid of circles (a) vs. see columns of circles (b)  Objects can be hidden or blurred o Hidden objects occur any time one object obscures part of another o Frequent in the environment, but ppl can easily adapted  understand part of object covered still exists o Unfocused objects ppl easily recognizable, computer more difficult  Objects look different from different viewpoints o Implication: images of objects continually changing, angel dependent o VIEWPOINT INVARIANCE – ability to recognize an object seen from o LAW OF GOOD CONTINUATION – points that when connected, result in straight or smoothly curving lines are seen as belonging together, different viewpoints and the lines tend to be seen in such a way as to follow the  Easy for humans; for computer not as obvious smoothest path The Gestalt Approach to Object Perception  GESTALT PSYCHOLOGIST – Gestalt = whole configuration that can’t be described merely as the sum of its parts o Basis: the whole differs from the sum of its parts o Wilhelm Wundt = early attempts to explain perception (pre-Gestalt) o LAW OF PROXIMITY/NEARNESS – Things that are near each other  STRUCTURALISM – psychological approach, perception created by combining elements (SENSATIONS) appear to be grouped together  Ex. Arrange various dots in certain ways to create a face  ex. See two groups of 2 blue spots  Weakness: stroboscope, 2 different stimuli perceived as one moving (APPARENT MOVEMENT illusion)  No stimulation in the space btwn 2 stimuli  no o PRINCIPLE OF COMMON REGION – elements that are within the sensation to provide explanation for movement same region of space appear to be grouped together o PRINCIPLE OF UNIFORM CONNECTEDNESS – connected region of visual properties such as lightness, color, texture, or motion, is perceived as a single unit  Weakness: ILLUSORY CONTOURS representing edges of cube  Contours are illusory b/c they aren’t actually present in physical stimulus, vanish when place finger over circles o PRINCIPLE OF SYNCHRONY – visual events that occur at the same  Can’t structurally explain b/c no actual contour, can’t be time are perceived as belonging together  ex. Yellow lights blink on and off any sensation where contour is perceived o PRINCIPLE OF COMMON FATE – Things that are moving in the same direction appear to be grouped together  Similar to synchrony but synchrony can occur w/o movement  Elements also don’t have to change in the same direction  Ex. Assume block of birds flying in one direction = a unit  2 directions = 2 units o LAW OF FAMILIARITY – things that form patterns that are familiar or  Determined no left-right preference meaningful are likely to become grouped together  2. Symmetrical shapes seen as figures (a)  ex. Find 13 hidden faces  Ex. Red areas on left, yellow areas on right  change in perception from “rocks in a stream” or “trees  3. Smaller areas more likely seen as figure (b) (c) in a forest” to faces changes perceptual organization of  4. Meaningful areas more likely seen as figure (d) rocks and trees  Here dark area resemble waves  figure like  PERCEPTUAL SEGREGATION – the perceptual separation of one object from another, i.e. how objects are separated from the background o FIGURE GROUND SEGREGATION – when see separate object (the  The Gestalt “Laws” as Heuristics FIGURE) stands out from background(the GROUND) o Most perceptual psychologist prefer Gestalt “principles/heuristics” o Gestalt interests: determine properties of figure & ground which  b/c proposed Gestalt perceptual organization/segregation don’t causes perception of one separate from another make strong enough prediction to qualify as laws  1. Figure more “thing like”, memorable than ground o HEURISTICS – rules of thumb, provide best-guess solution to problem  2. Figure seen as being in front of ground  Reflect properties of the environment  3. Ground seen as uniform material, extends beyond figure  Faster than algorithms, b/c doesn’t require to overly observer  4. BORDER OWNERSHIP – contour separating figure from object to figure out shape ground appear belong to the figure, although its shared o ALGORITHM – procedure that is guarantee to solve a problem  Algorithm always correct, heuristics not guaranteed Recognition by Components Theory (RBC)  RECOGNITION BY COMPONENTS THEOR
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