Schiffman Chapter 10

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Schiffman Chapter 10
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Perceptual constancy

• Most perception is relative, not absolute
• If relationships stay constant, we perceive other
  aspects as constant
• Lightness constancychanges in amount of light
  reflected from object perceived in relation to
  amount of light reflected from surrounding
  objects/background this is why objects dont
  change lightness as room lights dimmed

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Perceptual constancy

• Size constancysize of object to its surroundings
  (including texture gradient) constant, even as
  distance, and retinal image size, changes
• To have size constancy, we must be able to
  perceive distances of objects their
  surroundings

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Ames room illusion

• Size constancy distorted by room that is
  different shape than it looks for more info, see
  Ames Room

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Perceptual constancy

• Shape constancysame principle as other
  constancies shape relative to shape
  (perspective) of surroundings

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Transactionalism

• Retinal images inherently ambiguouscould arise
  from numerous objects in world oriented in
  various ways
• Why do we tend to perceive in predictable ways?
• Transactions with environment teach us which ways
  to perceive

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Illusion based on assumptions

• Trapezoidal window illusion
• The Exploratorium's Online Exhibits

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Illusions of depth, distance, constancy

• Moon illusion
• Moon Illusion Demonstration Applet
• Various theories still hotly debated. If you
  really want to wade into debate, look here The
  Moon Illusion

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Size/distance illusions

• Muller-Lyer illusion
• Muller-Lyer Illusion
• Perspective theory one looks like receding
  edge other looks like edge coming toward you
  one that looks farther away must be longer
• However blind people feel the illusion
  tactually! Maybe we just average in the
  extended lines

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Size/distance illusions

• Ponzo illusion
• The Ponzo Illusion
• Could be distance illusion
• However could be that lines that approach
  borders look larger

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Horizontal-vertical illusion

• Sensation Perception (horizontal-vertical
  illusion)

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Contrast illusions

• Café wall illusion
• The Cafe Wall Illusion

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Misc. illusions

• http//www.ritsumei.ac.jp/akitaoka/index-e.html
• Counter-Rotating Spirals Illusion
• Amos Storkey - Visual Illusions
• Optical Illusions Visual Phenomena