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Sensation & Perception ch 9 > chapter 9 > Flashcards

chapter 9 Flashcards

1
Q

Violet wavelength

A

400-450nm

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2
Q

Blue WV

A

450 to 490nm (Short)

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3
Q

Green WV

A

500 to 575nm (Medium)

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4
Q

Yellow WV

A

575 to 590nm (Medium, Long)

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5
Q

Orange WV

A

590 to 620nm

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6
Q

Red WV

A

620 to 700nm Long

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7
Q

Function of colour signals

A
  • help us classify and identify objects, thus recognition of objects is quicker when objects are coloured appropriately. i.e.: purple banana vs yellow.
  • facilitates perceptual organization of elements into objects i.e.: tell one object from another in a scene- monkey picking fruit from a bush.
  • Thus, colour vision may provide evolutionary advantage in foraging for food
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8
Q

Colours we see

A

Basic: Red, yellow, green, blue, following which combinations of these colours would describe the array of these colours we perceive.

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9
Q

colours can be changed by

A

changing 3 things:

  • wavelength
  • intensity
  • saturation
  • WIS
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10
Q

How does intensity change colour

A
  • changes perceived brightness.
  • If all colour is absorbed we see black- dim.
  • If all colour is reflected we see white-bright.
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11
Q

How does saturation change colour

A

-adding white to colour results in less saturated colour.

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12
Q

How is colour determined?

A

determined by wavelengths that are reflected.

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13
Q

What are pure or unique colours, and why?

A

Red, yellow, green, blue. When we have all of these we can describe the full scope of colours we see, however, If we remove any one of the basic colours from the list, we cannot describe the full array. Colours like orange, violet etc are not needed to complete this decryption, Thus only the basic colours red, yellow blue and green are called ‘pure’ or ‘unique’ colours.

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14
Q

What colour/nm is the short wavelength end of the spectrum?

A

Violet (400nm) to Blue

*blue is short like you

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15
Q

What colours is the middle wavelength portion of the spectrum?

A

Green
*meendium wavelength
Yellow

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16
Q

What colours/nm is the long wavelength portion of the spectrum?

A

Yellow and Red/700

* The Yellow and red brick road is LONG!

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17
Q

example of reducing colour saturation…

A

add white to red and get pink- pink is less saturated (desaturated) than (from) red

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18
Q

Before changing wavelength, saturation and intensity of the visible colour spectrum, how many can we see?

A

200

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19
Q

After changing wavelength, saturation and intensity of the colour spectrum how many can we see?

A

Millions

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20
Q

How is colour of light and objects different?

A

Colour of light is related to wavelengths in the visible spectrum, but colours of objects are related to reflected wavelengths (opaque objects) or transmitted light for transparent objects.

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21
Q

The process when Chromatic colours such as blue green and red, occur when some wavelengths are reflected more than others.

A

Selective reflection (different for transparent objects)

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22
Q

What are Achromatic colours?

A

Contain NO HUES: white black and grey tones

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23
Q

When do Achromatic colours occur?

A

When light is reflected equally across the spectrum

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24
Q

What are Chromatic colours?

A

hues such as green blue or red which are reflected more than others through the process of selective reflection

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25
Q

What are reflectance curves?

A
  • plots of percentage of light reflected for specific wavelengths
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26
Q

How would a reflectance curve for a white piece of paper look like?

A

High on the reflectance scale with a relatively smooth, and nearly horizontal line across the wavelength spectrum

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27
Q

How would a reflectance curve for a tomato look?

A

Low on the reflectance scale until it reached the 590 on the wavelength scale at which point it would rise substantially into the red wavelengths, thus illustrating the tomatoes reflectance of red light.

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28
Q

White WV

A

Long medium and short

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29
Q

Describe Selective transmission: give example.

A

Transparent items such as liquid, plastics glass, etc- only some wavelengths pass through the object or substance.
example: cranberry juice: selectively transmits long WV length light and appears red.

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30
Q

How is selective transmission graphed?

A

on Transmission Curves

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31
Q

What does a transmission curve plot

A

percentage of light transmitted vs wavelength.

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32
Q

What can affect perceived colour of selective transmission?

A

Background colour of object

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33
Q

what is the key to understanding what happens when coloured lights (Blue and Yellow) are superimposed together onto a white surface?

A

All of the light that is reflected from the surface by each light when alone is also reflected when the lights are superimposed. Thus the wavelengths reflected by each light have an additive effect. When the result equates to ALL wavelengths being reflected you see white (which reflects short, medium and long wavelengths),

34
Q

describe additive colour mixture

A

When mixing lights causes MORE wavelengths to be reflected. (each light ADDS WV to the mixture) Thus, when lights are mixed together their wavelengths are added together and result in the perception of whatever that combination of wavelengths equates to.

35
Q

additive colour mixture is to________ as subtractive colour mixture is to __________

A

light , paint

36
Q

The key to understanding what happens when coloured paint mixes together is….

A

When both paints still absorb the same wavelengths they absorbed when alone, so the only wavelengths reflected are those reflected by both paints in common.

37
Q

describe subtractive colour mixture

A

When mixing paints, fewer wavelengths are reflected because each paint subtracts wavelengths to be reflected)

38
Q

When might a colour mixture appear black

A

If a blue paint ONLY REFLECTED BLUE and a yellow paint ONLY REFLECTED YELLOW, there would be no common colour reflected (green) so the perceived colour would be black.

39
Q

What are two theories of colour perceptions:

A
  1. Trichromatic Theory of Colour Vision

2. Opponent- Process Theory of Colour Vision

40
Q

This theory states “a lights wavelength is signalled by the pattern of activity of three receptor mechanisms”.

A

Trichromatic Theory of Colour vision

41
Q

Can a Monochromat see colour. Why?

A

No - the principle of invariance which states as once photon of light is absorbed, the identity of the wavelength is lost. The receptor only knows the total amount of light it has absorbed. Thus a person with one pigment can match any wavelength in the spectrum by adjusting intensity.of another wavelength and thus sees all of the wavelengths as shades of grey.

42
Q

can a person with Dichromat see colour? why

A

yes but they will not be able to see as many colours as a trichromat. Because the ration of response to different light intensities of these receptors is constant. If ratio of light absorption for a wavelength at 480 is 2:1 it will remain so irregardless of intensity. As such the visual system can use ratio information to differentiate these wavelengths from one another.

43
Q

What is someone with two receptors for colour vision called/

A

Dichromat

44
Q

What is someone with three receptors for colour vision called?

A

Trichromat

45
Q

What are most colour deficiency problems related to?

A

problems with receptors in the retina that are present at birth

46
Q

Monochromat

A

person who needs only one wavelength to match any color

47
Q

Dichromat

A

person who needs only two wavelengths to match any colour. Percieve some colour however at a lesser range than trichromats.

48
Q

Anamolous trichromat

A

needs three wavelengths in different proportions than normal trichromat- not as good as a trichromat at distinguishing between similar wavelengths

49
Q

Unilateral dichromat

A

trichromatic vision in one eye and dichromatic in other- great for helping determine how perception of colour varies between he two types of ‘chromats’

50
Q

Aspects of Monochromatic vision

A
  • poor visual acuity,
  • sensitivity to bright light,
  • rare genetic condition
  • only see white, black and grey
  • no functioning cones- only rods
  • True colour blindess
51
Q

Three types of Dichromatism- what are the two most common

A

Most common:

Protonopia & Deuteranopia, Tritanopia is the third

52
Q

The wavelength at which a dichromat perceives grey

A

the neutral point

53
Q

The neutral point for protanope and rates for males and females

A

492

males 1%, females, .02%

54
Q

The neutral point for deuteranopes and rates for males and females

A

498

males 1%, females, .01%

55
Q

the neutral point for tritanopes and rates for males and females

A

570
males .002%, females, .001%
*think of a good alpha for women and then double that for men

56
Q

How does a protanope perceive colour

A

perceives SHORT wavelengths of light as blue. As the wavelength is increased the blue becomes less and less saturated until it reaches the neutral point of 492. At this point they perceive grey. Above the neutral point the protanope perceives yellow which becomes less intense at the long wavelength.

57
Q

How does a Deuteranope perceive colour?

A

Similar to protonope - sees short wavelengths as blue and long as yellow. Major difference from protonopes is the neutral point is 498.

58
Q

How does a Tritanope perceive colour?

A

Perceives blue at short wavelengths, red at long wavelengths with a neutral point at 570.

59
Q

Explain how dichromatism is a sex linked colour deficiency

A

inherited through the a gene located on the x chromosome. These forms of colour deficiency are considered sex linked as, only one normal x gene is required to override colour deficiency on a X chromosome. Women have 2 X chromosomes thus, essentially have a second chance at counteracting a colour deficient gene on one x chromosome if a normal gene is found on the other x chromosome. men however only have one X chromosome, thus no opportunity to counteract the deficiency. Further, women who have the deficient gene on one X chromosome can pass it on to their male offspring. As such many more men than women are dichromats.

60
Q

Protonopes are missing which type of __________ pigment?

A

long wavelength visual pigment

61
Q

deuteranopes are missing which type of __________ pigment?

A

medium wavelength visual pigment

62
Q

Tritanopes are missing which type of __________ pigment?

A

short wavelength visual pigment

63
Q

Proposed Physiological cause of Dichromatisism

A

Dichromats are missing one visual pigment. The brain does not make distinctions between wavelengths by relative size of signals. Instead it utlityzes the information about the difference between pairs (ratios) of receptors. As such, with only information about the difference between 2 as opposed to three receptors, the brain has less information to make distinctions between the full array of colours typically perceived by trichromats.

64
Q

Trichromatic theory best explains activity at what level

A

responses of cones in the retina

65
Q

Opponent Process theory best explains activity at what level

A

Neural response for cells connected to cones which lie further up the optic nerve in the brain. responses are based on paired colours whereby one of the pairs is excitatory and one is inhibitory.

66
Q

The Trichromatic Theory of Colour Vision is based on what type of evidence

A

Psychophysical: measured how visual receptors responded to presentation of stimulus with incorporation of participants description f perception.

67
Q

The Opponent Process Theory of Colour vision is based on what type of evidence

A

Phenomenological: stimuli presented and people described what they saw.

68
Q

What is simultaneous colour contrast

A

Whereby, after seeing a green square one perceives a red square on a white background and vice versa. These after images demonstrate colours which are paired. i.e.: red and green, blue and yellow.

69
Q

opponent neurons are found in the

A

lateral geniculate nucleus (LGN) and retina

70
Q

A condition where a person cannot perceive colour caused by brain damage

A

Cerebral achromatopsia

71
Q

Is there a colour centre in the brain much like the FFA

A

It was originally thought so but after finding neurons responding to colour in the V1 area in the brain outside of the originally proposed V4 colour centre, and evidence of opponent neurons in other areas of the visual receiving area it has been determined that there is no single colour centre for the brain.

72
Q

Which type of opponent neuron has been suggested as best for perceiving colours within regions.

A

Single opponent neurons with centre surround receptive field.

73
Q

Which type of opponent neuron has been suggested as best for perceiving boundaries between different colours.

A

double opponent neurons with side by side regions for receptive fields.

74
Q

color constancy.

A

we perceive colours as being relatively constant despite changes in illumination. This phenomena has not been explained yet by science however suggestions have been made.

75
Q

explanations for colour constancy in varying types of illumination

A

Chromatic Adaptation
Effect of surroundings
Memory of colour

76
Q

perception white grey and black remaining constant despite being under different illumunation

A

lightness constancy

77
Q

lightness constancy is determined by

A

intensity of illumination and objects percentage or ratio of reflectance NOT amount of reflectance

78
Q

ratio principle is

A

as long as ratio of the objects reflectance remains constant, the perceived lightness will remain the same

79
Q

a change in reflectance of light due to different materials

A

a reflectance edge

80
Q

An edge created by a change in illumination

A

a illumination edge (shadow)

81
Q

What is a penumbra and what does it signal

A

Penumbra of shadows is a fuzzy border around the shadow-signals an illumination edge and tells us this is a shadow not a separate object.

Sensation & Perception ch 9 (1 decks)

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