IV: Visual Organization and Interpretation

✤ Describe Gestalt psychologists’ understanding of perceptual organization, and explain how figure-ground and grouping principles contribute to our perceptions

✤ Explain how we use binocular and monocular cues to perceive the world in three dimensions and perceive motion

✤ Explain how perceptual constancies help us organize our sensations into meaningful perceptions

✤ Describe what research on restored vision, sensory restriction, and perceptual adaption reveals about the effects of experience on perception

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Gestalt

An organized whole. Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes.

✤ Filtering incoming information and we construct perceptions

✤ Mind matters

✤ In perception, the whole may exceed the sum of its parts

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Form Perception

✤ Figure-ground

The organization of the visual field into objects (the figures) that stand out from their surroundings (the ground) Example: ‘say’ ‘face/vase’

✤ Grouping

Our minds bring order and form to stimuli by following certain rules

We need to make things meaningful. 3

How do we recognize things?

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We group nearby figures together.

We fill in gaps to create a complete, whole object.

We perceive smooth, continuous patterns rather than discontinuous ones.

Examples of Grouping

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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 partly innate (discovered by Eleanor Gibson & Richard Walk)

✤ Created visual cliff experiments

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How do we perceive depth?

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Visual Cliff

A lab device for testing depth perception in infants and young animals

✤ 6-14 month old infants were coaxed by their mothers to crawl over the glass

✤ Most infants refused, indicating they could perceive depth

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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

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Two eyes are better than one

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Binocular Cues

Monocular Cues

Depth cues, such as interposition and linear perspective, available to either eye alone

- Judging how far away an object is by using just one eye.

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Needed to judge greater distances

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Monocular Cues

Motion Perception

Brain computes motion based partly on its assumption that shrinking objects are retreating and enlarging objects are approaching.

Phi Phenomenon:

Illusion of movement created when two or more adjacent lights blink on and off in quick succession.

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“Sometimes I wonder: Why is that Frisbee getting bigger? And

then it hits me! - Anonymous

What would life be like without motion?

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Monocular Cues

Relative  Size:    

If  two  objects  are  similar  in  size,  we  perceive  the  one  that  casts  a  smaller  retinal  image  to  be  farther  away.

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Monocular Cues

Interposition:    

Objects  that  occlude  (block)  other  objects  tend  to  be  perceived  as  closer.

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Monocular Cues

Relative height:

We perceive objects higher in our field of vision as farther away.

✤ We assume the lower part of a figure-ground illustration is closer, we perceive it as a figure.

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Monocular Cues

Light & shadow:

Shadows and highlights can provide clues to an object’s depth and dimensions.

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Monocular Cues

Monocular movement parallax (Relative Motion):

When our heads move from side to side, objects at different distances move at different speeds, or relative velocity.

✤ Closer objects move in the opposite direction of the head movement, and farther objects move with our heads.

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Perceptual constancies

How do Perceptual constancies help us organize our sensations into meaningful perceptions?

Perceptual Constancy (Top down processing)

Perceiving objects as unchanging (having constant shapes, size, brightness, and color) even as illumination and retinal images change

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How to recognize objects without being deceived

https://www.asdk12.org/MiddleLink/LA/reading/other/I_cdnuolt_blveiee.pdf

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Perceptual Constancy

Color Constancy

perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object.

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Example: apple in a bowl surrounded by other fruits.

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Perceptual Constancy

Shape Constancy

shape seems to change shape with the angle of our view

✤ we perceive the shape as constant, even while our retinas receive changing images to them

18Example: Rotating plate

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Perceptual Constancy

Size Constancy

Perceive objects as having a constant size, even while our distance from them varies.

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Example: Moon illusion

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Perceptual Adaptation

Visual ability to adjust to an artificially displaced visual field (prism glasses)

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Visual Interpretation: Immanuel Kant: knowledge comes from

inborn ways of sensory processing. John Locke: through our experiences we

learn to perceive.

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