04.12_Perception2 - All rights reserved 2 • The visual...

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© S. J. Luck All rights reserved 1 © S. J. Luck All Rights Reserved Perception II • Illusions are useful in the study of perception because there may be many ways to perceive something correctly, but only a few ways to make a speciFc pattern of errors • The goal of studying illusions is not to understand the illusions, but is instead to understand the algorithms and heuristics of normal perception This is called lightness constancy , because we see the lightness of an object surface as being the same (constant) regardless of the intensity of the light source Stimulus Viewed In Full Sunlight Stimulus Viewed Under Candlelight • As originally discussed by J.J. Gibson, motion provides important cues about several things: – ±igure-ground segmentation – Distance (motion parallax) – 3-dimensional structure – Speed of approach (looming)
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© S. J. Luck
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Unformatted text preview: All rights reserved 2 • The visual input is a 2-dimensional array of brightness and color values -- where are the object boundaries? 30,0,90 32,0,90 33,50,90 40,50,90 38,50,94 20,5,90 23,0,80 20,50,90 18,50,98 20,50,99 10,10,90 14,10,23 10,10,90 12,8,92 12,12,94 10,0,90 23,8,26 26,12,71 23,9,90 21,8,92 12,0,85 36,6,38 39,18,72 33,7,85 31,2,85 13,0,80 49,9,80 48,7,71 47,6,80 45,9,80 • A Demonstration: “X Marks the Spot” • Dilation & Contraction • The motion effects that underlie Fgure-ground segregation, contraction & dilation, and motion parallax combine to allow the perception of 3-D shape from motion cues • Example: Ultrasound © S. J. Luck All rights reserved 3 Movement of Object Toward Eyes Size of Retinal Image Far Small Large Near Figure/Ground Segregation 3-D Shape from Motion Dilation & Contraction Motion Parallax Looming...
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This note was uploaded on 11/08/2010 for the course PSC PSC100 taught by Professor Luck during the Spring '10 term at UC Davis.

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04.12_Perception2 - All rights reserved 2 • The visual...

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