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Sensation and perception > lecture 7 > Flashcards

lecture 7 Flashcards

1
Q

what animals have hardware to see colour in a way comparable to us?

A

catarrhine monkeys

platyrrhine monkeys

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2
Q

how many receptor types do humans have?

A

three (trichromats)

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3
Q

how many receptor types and some tropical fish have?

A

4 types (tetrachromatic)

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4
Q

how many receptors to pigeons have?

A

five, pentachromats

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5
Q

what is colour good for?

A

scene segmentation
camouflage
perceptual organisation
food identification

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6
Q

scene segmentation

A

variations in colour often signal object boundaries

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7
Q

camouflage

A

animals use this fact to disguise themselves by colour markings

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8
Q

perceptual organisation

A

our visual system uses colour to group elements in a scene

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9
Q

food identification

A

ripe fruit
correct leaves
harmless vs harmful berries
poisonous or venomous animals

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10
Q

what is colour

A

wavelength in the visible lights segment of the electromagnetic spectrum

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11
Q

what is the range of the visible light spectrum?

A

range from red (long wavelength light) to violet (short wavelength light)

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12
Q

how long is the entire electromagnetic spectrum?

A

1mm (1,000,000nm)

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13
Q

how much of the EM spectrum does visible light cover

A

just 400nm

4/1000 of a mm

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14
Q

what range do we see between (m)

A

0.00000750m and 0.00000390m

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15
Q

what is the colour of an object dependent on?

A

the wavelengths of light the object absorbs and reflects

the light source

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16
Q

what does wavelength of light reflected determine

A

only the hue

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17
Q

what is perceived colour determined by, other than hue?

A

intensity of reflected light

saturation of the colour

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18
Q

physiological attribute of wavelength

A

hue (colour)

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19
Q

physiological attribute of intensity

A

brightness, perceived intensity

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20
Q

physiological attribute of spectral purity

A

saturation

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21
Q

saturation

A

how much white light is mixed in with the pure hue

22
Q

what is the difference between red and blue

A

hue

23
Q

what is the difference between light blue and dark blue (usually)

A

intensity

24
Q

what is the difference between red and pink?

A

saturation

25
Q

trichromatic theory hypotheses:

A

1) there are 3 sorts of receptors that respond best to different wavelengths of light
2) colour you see determined by levels of activity in three sorts of receptors
e. g. red objects reflect more long wavelength light than other objects, so red receptors more active

26
Q

what are the threes receptor types? trichromatic theory

A

long (red)
medium (green)
short (blue)

27
Q

s cones respond best to wavelength:

A

419 nm

28
Q

m cones respond best to wavelength:

A

531 nm

29
Q

l cones respond best to wavelength:

A

558 nm

30
Q

support for trichromatic theory:

A

three primary colours combine to give all possible colours

three forms of dichromatism (colour-blindness)

A mixture of green and red light produces the same perception of yellow colour as monochromatic yellow light (metamerism)

31
Q

what determines which wavelength a cone will respond best to?

A

pigments in the cones

32
Q

how is light encoded from the cones

A

as an electrical signal

33
Q

is your red the same as my red?

A

explanatory gap, we will never know
example of pain
if people have different tastes in colour, does that suggest colours appear different to each other

34
Q

afterimages

A

only red and green cones can respond because the blue cones have become fatigued, this produces yellow afterimages

35
Q

what did hering notice>?

A

when people are presented with a large number of colour samples and asked to pick those that are pure, they pick a red, a green, a blue and ALSO a yellow

36
Q

opponent process theory proposal

A

there are three processes that are opponent in nature
-red/green
-yellow/blue
-black/white
each receptor will signal one colour, but not the other

37
Q

support of opponent process theory

A

non existence of certain colours e.g., blueish-yellow

colour confusion in colour blindness (red and green)

complementary colour images

colour context effects

lightness constancy

38
Q

lightness constancy:

A

perceive a colour as different depending on surroundings even though the reflected amount of light is the same

39
Q

what level does the trichromacy theory occur at?

A

the level of the cones

40
Q

what level does the opponent, process theory occur at?

A

LGN in the cortical cells

41
Q

who was colour blindness first described by?

A

John Dalton in 1794

42
Q

what should colour blindness be called and why?

A

colour deficiency

colour blind people just exhibit colour confusions, their experience of colour is different from normal

43
Q

cortical colour blindness

A

view world in black and white

44
Q

anopias

A

insensitive to s, m or l wavelengths of light (missing a type of cone)

45
Q

dichromatism

A

type of anopia

missing cones

46
Q

protanopia

A

L- cone pigment missing

  1. 3% men
  2. 02% F
47
Q

deuteranopia

A

M cone pigment missing

  1. 2% M
  2. 01% F
48
Q

tritanopia

A

S-cone pigment missing

  1. 001% M
  2. 003% F
49
Q

anomalies

A

misalignment of L or M in trichromats

-distribution or deficiency

50
Q

protoanomoly

A

L cone pigment deficiency
1.3% M
0.02% F
need more red in red-green mixture to match yellow

51
Q

deuteranomaly

A

M cone pigment deficiency
-5% M
-0.35% F
need more green in red green mixture to match yellow

52
Q

human tetrachromats

A

very rare in humans
they are predominately female
have 4 pigment cone types
can detect variations in hue that we normally cannot

Sensation and perception (12 decks)

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