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Module 19: Visual Organization and Interpretation

Visual Organization

19-1: How did the Gestalt psychologists understand perceptual organization, and how do figure-ground and grouping principles contribute to our perceptions?

  • When people are given a cluster of sensations, they tend to organize them into a gestalt (Figure 19.1)
    • ^^Gestalt:^^ an organized whole. Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes.

Form Perception

  • Our first perceptual task is to perceive any object (the figure) as distinct from its surroundings (the ground)
    • ex: as you read, the words are the figure; the white paper is the ground
    • Sometimes the same stimulus can trigger more than one perception
    • ^^figure-ground:^^ the organization of the visual field into objects (the figures) that stand out from their surroundings (the ground)
  • Our second perceptual task is ^^grouping:^^ the perceptual tendency to organize stimuli into coherent groups
    • Our minds bring order and form to stimuli by following certain rules for grouping
    • Proximity: We group nearby figures together.
      • We see not 6 separate lines, but 3 sets of 2 lines
    • Continuity: We perceive smooth, continuous patterns rather than discontinuous ones.
      • This pattern could be a series of alternating semicircles, but we perceive it as 2 continuous lines--one wavy, one straight
    • Closure: we fill in gaps to create, whole object.
      • Thus we assume that circles on the right are complete but partially blocked by the illusory triangle. Add nothin more than little line segments to close off the circles and your brain stops constructing a triangle. Such principles usually help us construct reality

Depth Perception

19-2: How do we use binocular and monocular cues to perceive the world in three dimensions and perceive motion?

  • ^^Depth perception^^: the ability to see objects in three dimensions although the images that strike the retina are two-dimensional; allows us to judge distance
    • Depth perception is developed at, or very soon after, birth
    • ^^visual cliff^^: a laboratory device for testing depth perception in infants and young animals
  • ^^Binocular cues^^: depth cues, such as retinal disparity, that depend on the use of two eyes
    • ^^Retinal disparity:^^ a binocular cue for perceiving depth: By comparing images from the retinas in the two eyes, the brain computes distance--the greater the disparity (difference) between the two images, the closer the object
    • Ex: figure 19.4
  • ^^Monocular cues:^^ depth cues that let us judge depth using information transmitted by only one eye.
    • Includes relative size, interposition, relative motion, relative height, and light and shadow
    • ex: figure 19.5
  • Your brain computes motion based partly on its assumption that shrinking objects are retreating and enlarging objects are approaching.
    • We are imperfect at motion perception
    • Large objects, like trains, appear to move more slowly than smaller objects, like cars, moving at the same speed
  • A quick succession of images on the retina can create an illusion of movement, as in stroboscopic movement or the phi phenomenon
    • ^^Phi phenomenon:^^ an illusion of movement created when 2 or more adjacent lights blink on and off in a quick succession

Perceptual Constancy

19-3: How do perceptual constancies help us organize our sensations into meaningful perceptions?

  • ^^Perceptual constancy:^^ a top-down process, perceiving objects as unchanging (having consistent shapes, size, brightness, and color) even as illumination and retinal images change
    • ^^Color constancy^^: our ability to perceive consistent color in objects, even though the lighting and wavelengths shift
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    • Brightness (or lightness) constancy is our ability to perceive an object as having a constant lightness even when its illumination changes
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    • Our brain constructs our experience of an object’s color our brightness through comparisons with our surrounding objects
    • Shape constancy is our ability to perceive familiar objects (such as an opening door) as unchanging in shape
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    • Size constancy is perceiving objects as unchanging in size despite their changing retinal images.
  • Knowing an object’s size gives us clues to its distance; knowing its distance gives clues about its size, but we sometimes misread monocular distance cues and reach the wrong conclusions, as in the moon illusion.
    • Moon illusion: the moon looks up to 50% larger when near the horizon than when in the sky
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Visual Interpretation

19-4: What does research on restored vision, sensory restriction, and perceptual adaptation reveal about the effects of experience on perception?

  • Experience guides our perceptual interpretations
    • ex: people blind from birth who gained sight after surgery lack the experience to visually recognize shapes, forms, and complete faces
  • Sensory restriction research indicated that there is a critical period for some aspects of sensory and perceptual development. Without early simulation, the brain’s neural organization does not develop normally.
  • People given glasses that shift the world slightly to the left or right, or even upside-down, experience perceptual adaptation. They are initially disoriented, but they manage to adapt to their new context
    • ^^perceptual adaptation^^: the ability to adjust to an artificially displaced or even inverted visual field