Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Perception Block 12 > Color Vision I > Flashcards

Color Vision I Flashcards

1
Q

The ability to discriminate colors

A

Color vision

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Evolution of color vision

A

May have evoked in primates by conferring a competitive advantage to monkeys in foraging for edible tropica fruits and leaves

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is chromatic contrast good for

A

Allows us to see objects that would otherwise be indistinguishable from the background in which they exist
-greatly adds to our visual capabilities

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Trichromatic theory

A
  • Thomas young
  • hypothesized that color information is encoded by a limited number of cones, perhaps 3
  • the relative activities of these differnt cones encode color
  • referred to as the trichromatic theory
  • it’s initial support came from psychophysical color matching experiments
  • more plausible theory than thousands of cones
  • does basis of modern color vision science
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

A person with only one photopigment

A

Monochromacy

-no color discrimination

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Principle of univariance

A

Photopigment molecule absorbs a light quantum, it does not encode the wavelength of that quantum, all information regarding its wavelength is lost.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

In monochromacity, what is the probability of Ya being absorbed

A

0.25

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

In monochromaicity, what is the probability of Yb being absorbed

A

0.50

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How does a monchromat tell difference in color

A

Ya and Yb are perceived as being differnt brightnesses, and they probably interpret this as a difference in color

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How would a monchromat not be able to distinguish Ya and Yb?

A

Double the intensity of the patch with Ya such that it now emits 200 quanta, but keep Yb at the same intensity

  • now they both result in 50 quintal absorption’s for each wavelength
  • both produce the same effect on the visual system
  • indistinguishable
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

People with monochromatic Vision are unable to make distinctions based on

A

Wavelength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How are monochromats able to correctly label colors under certain conditions?

A

We show three patches of light to a person who only has rods (a person with rod monchromacy)

  • 505, 570, and 620nm, each of which emits 5000 quanta
  • tell the subject that one patch is green, one is yellow, and one red
  • rhodopsin’s peak absorption is 507nm
  • patient reports the 505 is bright, 570 is less bright, and the 620 patch is dim
  • ask the subject to assign green, yellow, and red color labels to the patches of light, he or she might be able to do so correctly
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How does someone with monochromatic vision label colors

A

Use brightness to label colors

  • the person has noticed that other people have labeled dim objects red, and bright objects green, San has learned to label colors on the basis of brightness
  • when confronted with natural objects, such as apples and bananas, the tanks of color labeling may be easier by the presence of other cues, such as the shape of the fruit
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Does someone with rod monochromacy perceive colors?

A

Not easy tp answer
-we know that people with monochromatic vision can be fooled if we adjust the intensities of stimuli, they do not have the ability to distinguish stimuli on the basis of the wavelength alone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Dichromacy curves

A
  • the person has two photopigment, M and L
  • each peak at different wavelengths
  • have overlapping absorption spectra throughout much of the spectrum
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Number of quanta absorbed for M at Ya (dichromat)

A

60%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Number of quanta absorbed for L in Ya (dichromat)

A

20%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Number of quanta absorbed in Yb for M (dichromat)

A

40

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Number of quanta absorbed in Yb for L

A

60

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

In dichromacy, if the individual is shown two patches of light, one consisting of Ya and other Yb, the subject is asked to adjust the intensity of Yb so that the two patches appear identical

A

If capable of matching these two wavelengths, the person does not have the ability to make wavelength-based discriminations
-if the person is unable to match these two patches of light, he or she possess the ability to make discrimination based purely on wavelength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

It is possible for a dichromat to match Ya and Yb intensities?

A

No

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Why can a dichromat not match intensities of Ya and Yb?

A
  • there is no intensity at which the number of quanta absorbed by M and L or Yb equals the number absorbed by these same photopigment for Ya
  • no matter how the intensities of these two patches of light adjusted, they never have identical effects on the visual system
  • they are distinguishable because they are different wavelengths
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Can a dichromat adjust the intensities of the Ya/Yc, and Yb such that each patch of light results in the same number of quanta absorption’s by photopigment M and L?

A

Yes

  • each patch produces 200 quanta absorption’s by photopigment M and 300 by L
  • from the subjects perspective, these two patches of light, which are physically different, appear identical
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Two stimuli that appear identical, but are physically difference

A

Metamers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

How do dichromat a limited amount of color discrimination?

A

A patch of Ya always looks different than a patch of Yb

  • a patch of Yb may be matched by the proper combination of Ya and Yc
  • given at least three wavelengths divided into two patches, a dichromat is able to adjust th relative intensities of these wavelengths until the patches appear identical
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

Three difference photopigment with overlapping absorption spectra rather than two

A

Trichromatic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

Mono, di, or trichromacy shows superior wavelength discrimination

A

Trichroamcy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

Given at least four wavelengths divided into two patches, a person with _____vision is able to adjust the relative intensities of these wavelengths such that the two patches appear identical

A

Trichromatic vision
-the two patches appear identical because they result int he same number of quantal absorption’s by each of the three photopigment, they are metamers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

For three wavelengths divided into two patches, a person with ______ can match the patches, while a person with _____ cannot

A

Dichromacy
Trichromacy

This demonstrates the super color discrimination found in trichromacy
-there are limitations in trichromatic vision

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Limitations to trichromacy

A

If given four wavelengths divided into two patches, a person with trichromatic vision will be abel to match the patches

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Each molecule of cone photopigment consists of

A

The chromophore and an opsin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Cone chromophore

A

Ie retinal, an aldehyde derivative of retinol (vitamin A)

  • identical for all cone pigments
  • absorption of a light quantum by the chromophore initiates a series of events leading to vision
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Cone opsin

A

Interlaced into the disc membrane of the outer segment

  • determines absorption characterics of photopigment molecule
  • visually inert chain of amino acid
  • each class of cones has a differnt opsin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

M and L opsin genes are found on the ____ chromosome

A

X
-consistent with the sex linked inheritance of color vision deficiencies in which either the M or L cone photopigment is missing or altered

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

The S cone photopigment gene is located on

A

Chromosome 7

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

The rhodopsin gene is found on

A

Chromosome 3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

The cone photopigment genes and the rhodopsin gene

A

They are homologous

-suggests that all 4 share the same derivation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Which cone opsins are the the most similar

A

M and L

-indicative of recent duplication

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

The homology of the S cone opsin gene to the M and L cone opsin gene is

A

40%

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

How many copies of the L and M cone opsin gene does the X chromosome typically have

A

One copy of the L cone opsin and one or more copies of the M cone opsin gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Does having more than one copy of the M cone opsin gene affect color matching?

A

No

-there role is not understood at this time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

S cone absorption

A

426

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

M cone absorption

A

530

44
Q

L cone absorption

A

Two variants

  • one at 552
  • one at 557
45
Q

Three perceptual dimensions

A

Hue
Saturation
Brightness

46
Q

Hue

A

Laypersons term for color

47
Q

Saturation

A

Fullness or purity of color

48
Q

Physical dimension of hue

A

Wavelength

49
Q

Saturation physical dimension

A

Both wavelength and the amount of white in the mixture

50
Q

Brightness physical; dimensions

A

Radiance

51
Q

Perception that is most closely assocauted with wavelength

A

Hue

  • 540=green
  • 570=hue of yellow
52
Q

Most monochromatic stimuli change _____ slightly as their intensity is adjusted

A

Hue

  • there are however three wavelengths that do not change hue as their intensity is increased
  • invariant wavelengths
53
Q

Invariant wavelgnthns

A

Three wavelengths that do not change hue as their intensity is increased

  • blue at 478
  • green at 503
  • yellow ar 578
54
Q

Hues associated with invariant waverlgntsh are called

A

Unique hues

55
Q

Invariant blue

A

478

56
Q

Invariant green

A

503

57
Q

Invariant yellow

A

578

58
Q

How can we predict effect of increased intensity on hue

A

Stimuli with a wavelength that is shorter than unique green appear more blue as their intensity is increased

  • stimuli longer than 503 appear more yellow as their intensity is increased
  • a possible physiological basis for this phenomenon is provided by opponent color theory
59
Q

Desaturated color

A

Pastel, appears to be mixed with white and is not as bold

60
Q

Saturated color

A

Appears full in color

61
Q

Monochromatic stimuli are more _____ than stimuli that are mixed with white

A

Saturated

62
Q

Saurtation is _____ dependent

A

Wavelength

63
Q

Brightness sensation closely follows the _________ function

A

Photopicluminance function

64
Q

Under photopic conditions, a ______ stimulus is perceived as brighter than other equal energy monochromatic stimuli

A

555

65
Q

Bipartite

A

Split field

66
Q

Regions of best wavelgnth discrimination are at about ____and ____

A

495 and 590

-two wavelengths are differnt hues even if their wavelengths are just a few nanometers differnt

67
Q

Where is hue discrimination poor

A

In the short wavelgnth spectrum

68
Q

What is the wavelgnth discrimination curve sometime called

A

W curve of color discrimination

69
Q

Why do wavelgnth discrimination thresholds vary across the spectrum

A

It may be color discrimination is best where the slopes of the cone absorption spectra change most rapidly with respect to each other

70
Q

Color constancy

A

Whether viewed indoors under incandescent or fluorescent lights or outdoors in natural sunlight, the shirts color appear almost the same

71
Q

Assist us in IDing objects as lighting conditions vary

A

Color constancy

72
Q

What is color constancy advantageous for

A

For animals gather fruit in different lightings

73
Q

Physiological basis for color constancy

A

Dunno

74
Q

Is color constancy absolute

A

No

As lighting conditions change, these are subtle, but important, changes in color appearance

75
Q

Opponent color theory

A

Red and green are not seen simultaneously, colors are either red or green, not red-green
-same for blue and yellow

Chtormatic stimulus elicits an after image of a complementary color
_red=green afterimage, blue=yelllow afterimage)

76
Q

Opponent color theory conclusions

A

Color is processed by bipolar hie channels referred to as the red-green and blue-yellow channels
-by bipolar, it is meant that at any given instant, the channel can signal only one of the two attributes it is capable of coding
-

77
Q

Electrpphysiological evidence for color opponency

A
  • discovered horizontal cells in the fish retina that are excited by certain wavelengths of light and inhibited by others
  • a form of color opponency
  • horizontal cells are graded
  • AP in the LGN, clamp next to cells
78
Q

Once cell is isolated in color opponency

A

The neurons response, as measured by its frequency of APs, is plotted as a function of wavelength

79
Q

Cell has color coding capabilities (electrophysiological evidnce for color opponency)

A

If the neuron is excited by a stimulus, we know the stimulus must be a long wavelgnth, reverse for short wavelgnth

80
Q

Since the cell repsonds to one portion of the spectrum with excitation and another portion with inhibition, it is referred to as

A

Color opponent

81
Q

Non-color opponent cells

A

Not inhibited by any wavelgnth and responds to all spectral stimuli with excitation

  • does not have color coding capability
  • 55 peak
82
Q

Tells us that three classes of cones are sufficiency to explain color matching data

A

Trichromacy

83
Q

Reveals that receptoral information is encoded in an opponent fashion at postreceptoral levels

A

Presence of color opponent neurons in the retina and LGN

84
Q

L and M cones popsicle each other to produce

A

L-M opponentcells

85
Q

S cones are opposed by an addition of L- and M-cones to produce

A

S-(L+M) opponent cells

86
Q

Re-green cells found in

A

Fovea

87
Q

Parvo

A

Red-green

88
Q

Konio

A

Yellow blue

89
Q

Magno

A

Non-color opponency

90
Q

International authority on light, illumination, color, and color spaces

A

CIE

91
Q

Primate color vision

A

Trichromatic, with the trichromatic signal encoded in an opponent fashion

  • may occur very early in the visual system, at the level fo the bipolar cells in the primate
  • established that hue information is encoded by color opponent neurons
92
Q

CIE color system is based on

A

Trichromacy of vision

93
Q

A color is specified by the relative amounts of

A

Three primaries, which when mixed together, preduce the color

94
Q

Calculating a color

A

Coordinating Z is calculated by subtracting the sum of x and y from 1

X, y, z all add up to y

95
Q

What is the chromaticity CIE diagram is useful for what

A

Determining the result of mixing different wavelgnth stimuli together

96
Q

What is the result of mixing together equal amounts of 510 and 560nm?

A

530nm
-draw line connecting 560 and 510, draw a line from the W across the midway point of that line and then up and that gives you your wavelength

97
Q

Excitation purity

A

Tells if its closer to white (lower) or closer to the color (higher up)

A/(a+b)

98
Q

How to find the wavelgnth for a colors when you mix one part of a color and 3 parts of another color

A

Draw the line 3/4 of the way closer to the color with 3 parts from the W point.

99
Q

Complimentary colors, when mixed together, give you

A

White

100
Q

How do you find complement color on the graph?

A

Just draw a lien from the given wavelgnth through white onto the other side

101
Q

The CIE diagram specifies the relative amount of primaries necessary to

A

Match a color sample

102
Q

CIE primaries

A

Are imaginary

103
Q

The CIE system uses imaginary primaries to

A

Avoid the use of negative quantities

104
Q

Any set of color-matching functions, real or imaginary, can be converted to

A

Another set of real or imaginary functions

105
Q

Color is perceived along the perceptual dimensions of

A

Hue, saturation, and brightness

Perception Block 12 (6 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions