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Lecture Notes
Chapter 7

• Details of shape, colour, location, movement

• 3-D object recognition, object location, direction of movement

• Modules
  • Information from same region of retina
    • Receptive field
  • Neural circuits
    • Orientation, shape, movement, colour

• Cat, microelectrode, visual display

• First level subdivisions
  • Movement, orientation, width, colour of objects
• Second level subdivisions
  • Location and movement
  • Three-dimensional form perception

• Blind in some part of visual field
• Still able to perceive objects and background

• Perceptual problems
  • Colour, movement, location
  • Visual agnosia...can't recognize objects
    • Damage to VAC of temporal lobe
• Fine visual detail still available

• Objects and background

By: Stanford psychologist Roger Shepard

Other examples of the vase/profile.

An actual vase that encorporates this perceptual form

18th century French print; look for the face profiles towards the top

By M.C. Escher

Take this link for another interesting example of camouflage, this time of a Hidden Bird.

• Often, but not always, give form

Introducing boundaries

• Modifying verticies can change the illusion

Take this link to view the Triangle Completion Illusion, that highlights this issue of the importance of boundaries in identifying form.

• Detected object activates memory template
  • Search for exact match
• Simple model but...too simple

• Idealized patterns of particular objects
  • Don't need exact match
• May need multiple prototypes for specific objects

• Important physical features of familiar patterns
  • e.g., alphabetic characters
    

  • Two vertical, two diagonal lines
  • e.g., letter search
  

• Analysis and synthesis
• Problems:
  • Complexity...aids identification

• Combination of prototype and distinctive features models
• Geometric forms
• Combine into objects
• Visual system recognizes objects by identifying the sets of geons they contain
• Doesn't explain face recognition, specific objects

• Use of contextual information; "big picture"

• Use of elements; "data-driven"

Now?

• Motion parallax
• Pictorial cues
  • Interposition, size, linear perspective, texture, haze, shading, elevation Binocular cues
    • Convergence
    • Retinal disparity (stereopsis)
    Binocular cues
    • Convergence
      • For close objects
      • Turning of the eyes
    • Retinal disparity
      • Stereopsis
        • Images fall on different parts of the two retina
        • Neurons that receive signals from both eyes...only respond if disparity between input

Take this link to view some: Magic Eye Inc.

• Head movement
• Jump

Interposition

• One object in front of another

• Parallel lines recede and converge

• Coarser = closer; finer = distant

• Objects in distant less distinct, due to atmosphere

• Not good for absolute distance
• Which parts of objects are closer/farther

• Higher = more distant

Take this link to learn more about this Perceptual Ambiguity.