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Sensation and Perception > Color Vision: Moodle > Flashcards

Color Vision: Moodle Flashcards

1
Q

Light is :

A

An electromagnetic wave made up of multiple wavelengths

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2
Q

Light of different wavelengths is perceived as:

A

different colors

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3
Q

Color can be represented by:

A

Three primary colors

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4
Q

We can have __ versions of the primary colours

A

multiple

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5
Q

Light is usually:

A

heterochromatic (not usually monochromatic)

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6
Q

Monochromatic light can be depicted as having:

A

a single spike on the visible spectrum chart

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7
Q

fluorescent bulb:

A

appears to have no color associated to it but actually has some spikes (more greenish)

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8
Q

incandescent bulb:

A

also smooth but have less of the shorter wavelengths that sunlight has: as a result appears more orange/red than sunnlight

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9
Q

color is a __ construct

A

perceptual

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10
Q

Who said this:“The Rays to speak properly are not coloured. In them there is nothing else than a certain Power and Disposition to stir up a sensation of this or that Colour… So Colours in the Object are nothing but a Disposition to reflect this or that sort of Rays more copiously than the rest”

A

Isaac Newton

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11
Q

our perceptual experience of colour can be represented as two dimensions/properties:

A

(1) the hue
(2) the saturation
** brightnes is a seperate dimension corresponding to the perceived intensity of the light

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12
Q

What is the CIE color space:

A

It is a standardized color space where any color can be represented by a pair (X,Y) of coordinates

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13
Q

we can represent color in __ in the CIE color space

A

we can represent color in two dimension in this CIE color space: if we want to represent brightness we would need a third dimension)

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14
Q

The center of the CIE color space is where we see:

A

colorless or “white” light

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15
Q

At the bottom right of the CIE color space we find:

A

non spectral purples

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16
Q

nonspectral purples are :

A

NOT hues that can be evoked by single wavelength light (monochromatic light)

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17
Q

we can see nonspectral purples if:

A

we see light of different wavelengths mixed together

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18
Q

We perceive heterochromatic light to have the color corresponding to:

A

Its dominant wavelength

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19
Q

Who said this: “Who in the rainbow can draw the line where the violet tint ends and the orange tint begins? Distinctly we see the difference of the colors, but where exactly does the one first blendingly enter into the other? So with sanity and insanity”

A

Herman Melville, Billy Budd

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20
Q

Achromatic light (2):

A

Has no dominant wavelength
Is perceived as “being colorless”

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21
Q

What is an example of achromatic light?

A

white, grey and black have the same achromatic character: they are the same hue but different intensity (amount of light)

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22
Q

What is additive color?

A

We can create the perception of different colours by mixing the “primary” additive colours red green and blue

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23
Q

additive color works best with:

A

“pure” (monochromatic) colored light

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24
Q

One common application of additive color:

A

Digital displays:
Individual pixels are made uo of red, green and blue sub elements and intensity of suv elements is controlled so screen can evoke perceptions of different colors

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25
Q

What is subtractive colour:

A

Subtractive colour relies on light being absorbed : the colour is determined by what doesn’t get absorbred

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26
Q

What is an example of subtractive color:

A

process of mixing paints/inks, printed material

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27
Q

subtractive colour is called subtractive because it relies on:

A

the light being absorbed rather than the light being produced/transmitted

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28
Q

In general, for additive color, we want:

A

highly monochromatic and highly saturated primary color

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29
Q

In general, for subtractive color mixtures, we want:

A

*** to be confirmed

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30
Q

subtractive color will absorb:

A

most of the spectrum and allow particular band to pass through
ex: blue paint absorbs longer wavelength of color and reflects the short

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31
Q

nonspectral purples are:

A

colors that cannot be evoked by monochromatic light

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32
Q

Two objects with the same hue but different saturation would be perceived as:

A

more or less vivid but the same “colour”

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33
Q

computer screens are an application of :

A

additive color

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34
Q

metamers:

A

the idea that to different stimuli are physically different but perceived to be the SAME

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35
Q

evidence that we need three primary colours to match the wavelengths across the spectrum of visible light comes from:

A

metameric color-matching experiments

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36
Q

Is it possible to match the wavelengths from across the spectrum of visible light with one or two cones?

A

NO

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37
Q

A single type of photoreceptor can detect light but:

A

it lacks the ability to differentiate between wavelengths effectively (this limitation is overcome by having multiple types of photoreceptors working together to enable color vision

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38
Q

The photoreceptor will generate the same neural signal for:

A

-a less intense light at a wavelength it is more sensitive to
- a more intense light at a wavelength that it is less sensitive to

39
Q

People who are truly blind are:

A

Rod monochromats

40
Q

cone responses are color blind =

A

univariant

41
Q

With two different cones (of different sensitivities) we can:

A

differentiate wavelength and intensity using relative sensitivities BUT there WILL be some wavelengths that produce the same relative response

42
Q

How do we distinguish/ perceive different colors with two cones?

A

At the different wavelengths of test light you can see that we have a unique relative output from each of these cones: there is a unique combination of sensitivities for each wavelength that we can use to interpret the signals from these cones and produce a percept of color

43
Q

(most) humans are:

A

trichromats: 3 types of cones with different sensitivites

44
Q

most other mammals are:

A

dichromats (2 types of cones)

45
Q

some birds are:

A

tetrachromats (4 types of cones)

46
Q

the mantis shrimp is a :

A

hexadecachromat (16 types of cones)

47
Q

Why is it that we don’t have more and more cones to be able to distinguish colours with more accuracy and resolution?

A

It is a tradeoff between being able to perceive spatial detail in color and being able to differentiate between different wavelengths.
At least two cones with different sensitivities need to be illuminated by any sort of stimulus to differentiate color, the less spatial resolution you end up getting; all of the cones converge on a single photoreceptor which reduces the detail we can see because we have increased the receptive field of that ganglion cell and that particular V1 neuron that we are stimulating

48
Q

Is the distribution of s, m and L cones on the retina uniform?

A

The distribution is not uniforma and the distribution can vary quite a lot between different people

49
Q

total “colour blindness” is the result of either (2):

A

(1)Having one type of cone
(2)Only rods

50
Q

People with one type of cone:

A

Spatial acuity still good despite inability to distinguish color

51
Q

People with only rods (rod monochrats):

A

Poor spatial acuity
No ability to distinguish color

52
Q

___ is the more common form of “color blindness”

A

dichromacy

53
Q

The two more common types of dichromacy are:

A

Protonopia and deuteranopia

54
Q

How are protonopia and deuteranopia inherited?

A

X-linked: condition is more prevalent in males with one X chromosome

55
Q

dichromacy:

A

two types of cones

56
Q

Dichromacy in humans is divided into three types, depending on which cone is missing:

A

(1) Protonopia
(2) Deuteranopia
(3) tritanopia

57
Q

which of the three dichromacy conditions is the rarest:

A

tritanopia

58
Q

Protonopia:

A

First, or L-cone is missing

59
Q

Deuteranopia:

A

Second, or M-cone missing

60
Q

tritanopia:

A

Third, or S-cone missing

61
Q

How do people with protanopia or deuteranopia see the visible spectrum:

A

They see the spectrum with less difference between middle and long wavelengths

Still good ability to distinguish shorter wavelengths (lack M-cones and L-cones)

62
Q

How do people with tritanopia see the visible spectrum?

A

Opposite of those with protonopia and deuteranopia:difficulty to distinguish shorter wavelengths (lack S-cones)

63
Q

__ is more common than dichromacy

A

anomalous trichromacy

64
Q

anomalous trichromacy is more common than dichromacy, explain what it is:

A

more common than a complete lack of one of these cones is a slight difference in one of these cones: figure a: m and l sensitivity, m’ and l’ are possible genetic variation of that
if we get m’ and l’ which are quite close together: functionally because those two sensitivity profiles overlap so much it becomes a lot harder for those people to distinguish between colors at that end of the spectrum: as if they only one type of those types of cones

65
Q

What is the flipside of anomalous trichromacy:

A

since females have two X chromosomes, they can have both M and L and M’ and L’
-slight advantage to distinguish colors
- they are NOT true tetrachromats because the 4 cones are very close to each other in sensitivity
-these females are better at color discrimination tasks

66
Q

the neural signal from a single type of photoreceptor __ be used to infer the color of a stimulus

A

CANNOT

67
Q

People with protanopia don’t have:

A

L cones

68
Q

People with deuteranopia don’t have:

A

M cones

69
Q

___ proposed that there were three “mechanisms”, distinct from the three types of cones, that gave an output resulting from contrast/opponency between:

A

Both Erwald Herring and Ernst Mach

70
Q

Who conducted hue cancellation experiments

A

Dorothea Jameson and Leo Hurvich

71
Q

Hue cancellation experiments supported:

A

the opponency mode

72
Q

Example of hue cancellation experiments:

A

1.start with a yellowish green
2.add blue light until the green appears to have no yellow
3.when the green appears neither yellow nor blue, we are left with a unique green

73
Q

we have unique (pure) color wavelengths for which colors:

A

-blue
-green
-yellow

73
Q

What is the wavelength for a unique blue?

A

477 nm

74
Q

Do we have a unique (pure) colour wavelength for red?

A

No, unique red is not a point on the spectrum

75
Q

What is the wavelength for a unique green?

A

510 nm

76
Q

What is the wavelength for a unique yellow?

A

580 nm

77
Q

The three types of cones (S,M,L) form ___ connections to ganglion cells to form ___

A

The three types of cones (s,m,l) form excitatory or inhibitory CONNECTIONS to ganglion cells to form OPPONENT CHANNELS

78
Q

opponent mechanisms were proposed by :

A

Herring and Mach

79
Q

the S - ML pathway is excited by __ and inhibited by __

A

The S-ML pathway is excited by blue and inhibited by yellow

79
Q

L-M pathway ganglion cells have(2):

A

o annular receptive fields similar to the centre-on and centre-off receptive fields we’ve already seen (but with no inhibition if the centre colour is presented in the surround)
o colour-opponent ON and OFF regions

80
Q

The S-ML pathway has ___ receptive fields

A

Spatially uniform

81
Q

Where are the parvocellular, konicellular and magnocellular layers found?

A

In the LGN - lateral geniculate nucleus

82
Q

Layers 1 and 2 in the LGN are:

A

magnocellular layers

83
Q

Layers 3-6 in the LGN are the:

A

parvocellular layers

84
Q

Parvocellular layers of the LGN process:

A

The LM pathway

85
Q

Koniocellular layers of the LGN process:

A

the S-ML pathway

86
Q

Magnocellular layers process;

A

they do not process colour information

87
Q

Describe the parvocellular pathway (LM pathway):

A

-Projects to layer 4cb of the striate cortex
–Sends axons to layer 3, within the “blobs”

88
Q

Describe the koniocellular pathway (S-LM pathway):

A

-Projects to layer 3 of the striate cortex directly

89
Q

in comparison to the parvocellular pathway, the konicellular pathway projects to the striate cortex :

A

directly

90
Q

double opponent cells in V1 are inhibited if:

A

the preferred centre colour is presented in the surround

91
Q
A

Sensation and Perception (19 decks)

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