IV: Visual Organization and Interpretation

Transcription

1 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 1

2 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 2

3 Form Perception How do we recognize things? 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

4 Examples of Grouping We group nearby figures together. We fill in gaps to create a complete, whole object. We perceive smooth, continuous patterns rather than discontinuous ones. 4

5 Depth Perception How do we perceive depth? 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 5

6 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 6

7 Binocular Cues Two eyes are better than one 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 7

8 Binocular Cues 8

9 Monocular Cues Needed to judge greater distances 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. 9

10 Monocular Cues Motion Perception What would life be like without motion? Brain computes motion based partly on its assumption that shrinking objects are retreating and enlarging objects are approaching. Sometimes I wonder: Why is that Frisbee getting bigger? And then it hits me! - Anonymous Phi Phenomenon: Illusion of movement created when two or more adjacent lights blink on and off in quick succession. 10

11 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. 11

12 Monocular Cues Interposition: Objects that occlude (block) other objects tend to be perceived as closer. 12

13 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. 13

14 Monocular Cues Light & shadow: Shadows and highlights can provide clues to an object s depth and dimensions. 14

15 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. 15

16 Perceptual constancies How to recognize objects without being deceived 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 16

17 Perceptual Constancy Color Constancy perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the object. Example: apple in a bowl surrounded by other fruits. 17

18 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 Example: Rotating plate 18

19 Perceptual Constancy Size Constancy Perceive objects as having a constant size, even while our distance from them varies. Example: Moon illusion 19

20 Perceptual Adaptation Visual ability to adjust to an artificially displaced visual field (prism glasses) Visual Interpretation: Immanuel Kant: knowledge comes from inborn ways of sensory processing. John Locke: through our experiences we learn to perceive. 20