REVIEW Vision: Sensory and Perceptual Processing

Learning Objectives

Test Yourself by taking a moment to answer each of these Learning Objective Questions (repeated here from within the module). Research suggests that trying to answer these questions on your own will improve your long-term memory of the concepts (McDaniel et al., 2009).

Question

17-1 What are the characteristics of the energy that we see as visible light? What structures in the eye help focus that energy?
ANSWER: What we see as light is only a thin slice of the broad spectrum of electromagnetic energy. The portion visible to humans extends from the blue-violet to the red light wavelengths. After entering the eye and being focused by a lens, light energy particles strike the eye's inner surface, the retina. The hue we perceive in a light depends on its wavelength, and its brightness depends on its intensity.

Question

17-2 How do the rods and cones process information, and what is the path information travels from the eye to the brain?
ANSWER: Light entering the eye triggers chemical changes in the light-sensitive rods and color-sensitive cones at the back of the retina, which convert light energy into neural impulses. After processing by bipolar and ganglion cells, neural impulses travel from the retina through the optic nerve to the thalamus, and on to the visual cortex.

Question

17-3 How do we perceive color in the world around us?
ANSWER: According to the Young-Helmholtz trichromatic (three-color) theory, the retina contains three types of color receptors. Contemporary research has found three types of cones, each most sensitive to the wavelengths of one of the three primary colors of light (red, green, or blue). Hering's opponent-process theory proposed three additional color processes (red-versus-green, blue-versus-yellow, black- versus-white). Research has confirmed that, en route to the brain, neurons in the retina and the thalamus code the color-related information from the cones into pairs of opponent colors. These two theories, and the research supporting them, show that color processing occurs in two stages.

Question

17-4 Where are feature detectors located, and what do they do?
ANSWER: Feature detectors, located in the visual cortex, respond to specific features of the visual stimulus, such as shape, angle, or movement. Supercell clusters in other critical areas respond to more complex patterns.

Question

17-5 How does the brain use parallel processing to construct visual perceptions?
ANSWER: Through parallel processing, the brain handles many aspects of vision (color, movement, form, and depth) simultaneously. Other neural teams integrate the results, comparing them with stored information and enabling perceptions.

Question

17-6 How did the Gestalt psychologists understand perceptual organization, and how do figure-ground and grouping principles contribute to our perceptions?
ANSWER: Gestalt psychologists searched for rules by which the brain organizes fragments of sensory data into gestalts (from the German word for "whole"), or meaningful forms. In pointing out that the whole may exceed the sum of its parts, they noted that we filter sensory information and construct our perceptions. To recognize an object, we must first perceive it (see it as a figure) as distinct from its surroundings (the ground). We bring order and form to stimuli by organizing them into meaningful groups, following such rules as proximity, continuity, and closure.

Question

17-7 How do we use binocular and monocular cues to perceive the world in three dimensions?
ANSWER: Depth perception is our ability to see objects in three dimensions and judge distance. The visual cliff and other research demonstrate that many species perceive the world in three dimensions at, or very soon after, birth. Binocular cues, such as retinal disparity, are depth cues that rely on information from both eyes. Monocular cues (such as relative size, interposition, relative height, relative motion, linear perspective, and light and shadow) let us judge depth using information transmitted by only one eye.

Question

17-8 How do perceptual constancies help us construct meaningful perceptions?
ANSWER: Perceptual constancies enable us to perceive objects as stable despite the changing image they cast on our retinas. Color constancy is our ability to perceive consistent color in objects, even though the lighting and wavelengths shift. Brightness (or lightness) constancy is our ability to perceive an object as having a constant lightness even when its illumination—the light cast upon it—changes. Our brain constructs our experience of an object's color or brightness through comparisons with other surrounding objects. Shape constancy is our ability to perceive familiar objects (such as an opening door) as unchanging in shape. 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.

Question

17-9 What does research on restored vision, sensory restriction, and perceptual adaptation reveal about the effects of experience on perception?
ANSWER: Experience guides our perceptual interpretations. People blind from birth who gained sight after surgery lack the experience to visually recognize shapes, forms, and complete faces. Sensory restriction research indicates that there is a critical period for some aspects of sensory and perceptual development. Without early stimulation, 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.

Terms and Concepts to Remember

Test yourself on these terms.

Question

wavelength (p. 209)
hue (p. 209)
intensity (p. 209)
retina (p. 211)
accommodation (p. 211)
rods (p. 211)
cones (p. 211)
optic nerve (p. 211)
blind spot (p. 211)
fovea (p. 212)
Young-Helmholtz trichromatic (three-color) theory (p. 213)
opponent-process theory (p. 214)
feature detectors (p. 215)
parallel processing (p. 216)
gestalt (p. 217)
figure-ground (p. 217)
grouping (p. 217)
depth perception (p. 218)
visual cliff (p. 218)
binocular cues (p. 219)
retinal disparity (p. 219)
monocular cues (p. 219)
perceptual constancy (p. 221)
color constancy (p. 221)
perceptual adaptation (p. 223)
the distance from the peak of one light wave or sound wave to the peak of the next. Electromagnetic wavelengths vary from the short blips of cosmic rays to the long pulses of radio transmission.
the dimension of color that is determined by the wavelength of light; what we know as the color names blue, green, and so forth.
depth cues, such as interposition and linear perspective, available to either eye alone.
the point at which the optic nerve leaves the eye, creating a "blind" spot because no receptor cells are located there.
an organized whole. Gestalt psychologists emphasized our tendency to integrate pieces of information into meaningful wholes.
a laboratory device for testing depth perception in infants and young animals.
the perceptual tendency to organize stimuli into coherent groups.
the theory that the retina contains three different types of color receptors-one most sensitive to red, one to green, one to blue-which, when stimulated in combination, can produce the perception of any color.
the processing of many aspects of a problem simultaneously; the brain's natural mode of information processing for many functions, including vision.
perceiving familiar objects as having consistent color, even if changing illumination alters the wavelengths reflected by the objects.
the process by which the eye's lens changes shape to focus near or far objects on the retina.
depth cues, such as retinal disparity, that depend on the use of two eyes.
the nerve that carries neural impulses from the eye to the brain.
the organization of the visual field into objects (the figures) that stand out from their surroundings (the ground).
the amount of energy in a light wave or sound wave, which influences what we perceive as brightness or loudness. Intensity is determined by the wave's amplitude (height).
the ability to adjust to changed sensory input, including an artificially displaced or even inverted visual field.
the theory that opposing retinal processes (red-green, yellow-blue, white-black) enable color vision. For example, some cells are stimulated by green and inhibited by red; others are stimulated by red and inhibited by green.
retinal receptors that are concentrated near the center of the retina and that function in daylight or in well-lit conditions. Cones detect fine detail and give rise to color sensations.
nerve cells in the brain that respond to specific features of the stimulus, such as shape, angle, or movement.
the light-sensitive inner surface of the eye, containing the receptor rods and cones plus layers of neurons that begin the processing of visual information.
retinal receptors that detect black, white, and gray, and are sensitive to movement; necessary for peripheral and twilight vision, when cones don't respond.
perceiving objects as unchanging (having consistent color, brightness, shape, and size) even as illumination and retinal images change.
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.
the ability to see objects in three dimensions although the images that strike the retina are two-dimensional; allows us to judge distance.
the central focal point in the retina, around which the eye's cones cluster.

Experience the Testing Effect

Page 225

Test yourself repeatedly throughout your studies. This will not only help you figure out what you know and don’t know; the testing itself will help you learn and remember the information more effectively thanks to the testing effect.

Question 6.8

1. The characteristic of light that determines the color we experience, such as blue or green, is .

Question 6.9

2. The amplitude of a light wave determines our perception of

A.
B.
C.
D.

Question 6.10

3. The blind spot in your retina is located where

A.
B.
C.
D.

Question 6.11

4. Cones are the eye's receptor cells that are especially sensitive to ________ light and are responsible for our ________ vision.

A.
B.
C.
D.

Question 6.12

5. Two theories together account for color vision. The Young-Helmholtz trichromatic theory shows that the eye contains, ________ and the opponent-process theory accounts for the nervous system's having ________.

A.
B.
C.
D.

Question 6.13

6. What mental processes allow you to perceive a lemon as yellow?
ANSWER: Your brain constructs this perception of color in two stages. In the first stage, the lemon reflects light energy into your eyes, where it is transformed into neural messages. Three sets of cones, each sensitive to a different light frequency (red, blue, and green) process color. In this case, the light energy stimulates both red-sensitive and green-sensitive cones. In the second stage, opponent-process cells sensitive to paired opposites of color (red/green, yellow/blue, and black/white) evaluate the incoming neural messages as they pass through your optic nerve to the thalamus and visual cortex. When the yellow-sensitive opponent-process cells are stimulated, you identify the lemon as yellow.

Question 6.14

7. The cells in the visual cortex that respond to certain lines, edges, and angles are called .

Question 6.15

8. The brain's ability to process many aspects of an object or a problem simultaneously is called .

Question 6.16

9. Our tendencies to fill in the gaps and to perceive a pattern as continuous are two different examples of the organizing principle called

A.
B.
C.
D.

Question 6.17

10. In listening to a concert, you attend to the solo instrument and perceive the orchestra as accompaniment. This illustrates the organizing principle of

A.
B.
C.
D.

Question 6.18

11. The visual cliff experiments suggest that

A.
B.
C.
D.

Question 6.19

12. Depth perception underlies our ability to

A.
B.
C.
D.

Question 6.20

13. Two examples of depth cues are interposition and linear perspective.

Question 6.21

14. Perceiving a tomato as consistently red, despite lighting shifts, is an example of

A.
B.
C.
D.

Question 6.22

15. After surgery to restore vision, patients who had been blind from birth had difficulty

A.
B.
C.
D.

Question 6.23

16. In experiments, people have worn glasses that turned their visual fields upside down. After a period of adjustment, they learned to function quite well. This ability is called .

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