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PSYCH 202 Exam 2 > Chapter 6.5 > Flashcards

Flashcards in Chapter 6.5 Deck (19)
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1
Q

black

A

experienced when there is an absence of light.

2
Q

white

A

produced by an intense mixture of a wide range of wavelengths in roughly equal proportions.

3
Q

gray

A

produced by the same mixture at lower intensities.

4
Q

color

A

depends on the wavelengths of light that it reflects into the eye.

5
Q

Component theory (trichromatic theory) of color vision

A

proposed by Young but refined by Helmholtz; there are three different kinds of color receptors (cones), each with a different spectral sensitivity, and the color of a particular stimulus is presumed to be encoded by the ratio of activity in the three kinds of receptors. Derived from the observation that any color of the visible spectrum can be matched by a mixing together of three different wavelengths of light in different proportions.

6
Q

Opponent-process theory of color vision

A

proposed by Hering; suggested that there are two different classes of cells in the visual system for encoding color and another class for encoding brightness. Each of the three classes of cells encoded two complementary color perceptions.

7
Q

one class of color coding cells (opponent-process theory)

A

signaled red by changing its activity in one direction (e.g. hyperpolarization) and signaled red’s complementary color, green, by changing its activity in the other direction (e.g. hyperpolarization).

8
Q

another class of color coding cells (opponent-process theory)

A

signals blue and its complement yellow in the same opponent fashion.

9
Q

Opponent-process theory based on:

A

(1) Complementary colors cannot exist together.
(2) The afterimage produced by staring at red is green and vice versa and the after image produced by staring at yellow is blue and vice versa.

10
Q

Complementary colors

A

pairs of colors that produce white or gray when combined in equal measure.

11
Q

Cones each have a different photopigment

A

with its own characteristic absorption spectrum. Some are more sensitive to short, medium, or long wavelengths.

12
Q

At all subsequent levels of the retina-geniculae-striate system

A

there are cells that respond in one direction (e.g. increased firing) to one color and in the opposite direction (e.g. decreased firing) to its complementary color.

13
Q

Trichromats

A

most primates; possessing three color vision photopigments.

14
Q

Dichromats

A

most other mammals; possessing two color vision photopigments. Lack the photopigment sensitive to long wavelengths and thus have difficulty seeing light at the red end of the visible spectrum.

15
Q

color constancy

A

refers to the fact that the perceived color of an object is not a simple function of the wavelengths reflected by it. Tendency for an object to stay the same color despite major changes in the wavelengths of light that it reflects.

16
Q

Land

A

blue objects stay blue, etc., regardless of the wavelengths they reflect. This color constancy occurs as long as the object is illuminated with light that contains some short, medium, and long wavelengths and as long as the object is viewed as part of a scene, not in isolation.

17
Q

Retinex theory of color vision

A

Land; the color of an object is determined by its reflectance – the proportion of light of different wavelengths that a surface reflects. The visual system calculates the reflectance of surfaces, and thus perceives their colors, by comparing the light reflected by adjacent surfaces in at least three different wavelength bands (short, medium, long).

18
Q

Dual-opponent color cells

A

in the monkey visual cortex respond with vigorous “on” firing when the center of their circular receptive field is illuminated with one wavelength and the surround (periphery) is simultaneously illuminated with another wavelength. Display vigorous “off” firing when the pattern of illumination is reversed. In essence, they respond to the contrast between wavelengths reflected by adjacent areas of their receptive field. Not evenly distributed throughout the primary visual cortex.

19
Q

Livingstone and Hubel

A

found that dual-opponent color cells are concentrated in the primary visual cortex in peglike columns that penetrate the layers of the money primary visual cortex, with the exception of the lower layer IV. Many neurons are particularly rich in the mitochondrial enzyme cytochrome oxidase.