lecture 7

Question 1

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

Answer 1

catarrhine monkeys

platyrrhine monkeys

Question 2

how many receptor types do humans have?

Answer 2

three (trichromats)

Question 3

how many receptor types and some tropical fish have?

Answer 3

4 types (tetrachromatic)

Question 4

how many receptors to pigeons have?

Answer 4

five, pentachromats

Question 5

what is colour good for?

Answer 5

scene segmentation
camouflage
perceptual organisation
food identification

Question 6

scene segmentation

Answer 6

variations in colour often signal object boundaries

Question 7

camouflage

Answer 7

animals use this fact to disguise themselves by colour markings

Question 8

perceptual organisation

Answer 8

our visual system uses colour to group elements in a scene

Question 9

food identification

Answer 9

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

Question 10

what is colour

Answer 10

wavelength in the visible lights segment of the electromagnetic spectrum

Question 11

what is the range of the visible light spectrum?

Answer 11

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

Question 12

how long is the entire electromagnetic spectrum?

Answer 12

1mm (1,000,000nm)

Question 13

how much of the EM spectrum does visible light cover

Answer 13

just 400nm

4/1000 of a mm

Question 14

what range do we see between (m)

Answer 14

0.00000750m and 0.00000390m

Question 15

what is the colour of an object dependent on?

Answer 15

the wavelengths of light the object absorbs and reflects

the light source

Question 16

what does wavelength of light reflected determine

Answer 16

only the hue

Question 17

what is perceived colour determined by, other than hue?

Answer 17

intensity of reflected light

saturation of the colour

Question 18

physiological attribute of wavelength

Answer 18

hue (colour)

Question 19

physiological attribute of intensity

Answer 19

brightness, perceived intensity

Question 20

physiological attribute of spectral purity

Answer 20

saturation

Question 21

saturation

Answer 21

how much white light is mixed in with the pure hue

Question 22

what is the difference between red and blue

Answer 22

hue

Question 23

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

Answer 23

intensity

Question 24

what is the difference between red and pink?

Answer 24

saturation

Question 25

trichromatic theory hypotheses:

Answer 25

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

Question 26

what are the threes receptor types? trichromatic theory

Answer 26

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

Question 27

s cones respond best to wavelength:

Answer 27

419 nm

Question 28

m cones respond best to wavelength:

Answer 28

531 nm

Question 29

l cones respond best to wavelength:

Answer 29

558 nm

Question 30

support for trichromatic theory:

Answer 30

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)

Question 31

what determines which wavelength a cone will respond best to?

Answer 31

pigments in the cones

Question 32

how is light encoded from the cones

Answer 32

as an electrical signal

Question 33

is your red the same as my red?

Answer 33

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

Question 34

afterimages

Answer 34

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

Question 35

what did hering notice>?

Answer 35

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

Question 36

opponent process theory proposal

Answer 36

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

Question 37

support of opponent process theory

Answer 37

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

Question 38

lightness constancy:

Answer 38

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

Question 39

what level does the trichromacy theory occur at?

Answer 39

the level of the cones

Question 40

what level does the opponent, process theory occur at?

Answer 40

LGN in the cortical cells

Question 41

who was colour blindness first described by?

Answer 41

John Dalton in 1794

Question 42

what should colour blindness be called and why?

Answer 42

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

Question 43

cortical colour blindness

Answer 43

view world in black and white

Question 44

anopias

Answer 44

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

Question 45

dichromatism

Answer 45

type of anopia | missing cones

Question 46

protanopia

Answer 46

L- cone pigment missing 1. 3% men 0. 02% F

Question 47

deuteranopia

Answer 47

M cone pigment missing 1. 2% M 0. 01% F

Question 48

tritanopia

Answer 48

S-cone pigment missing 0. 001% M 0. 003% F

Question 49

anomalies

Answer 49

misalignment of L or M in trichromats | -distribution or deficiency

Question 50

protoanomoly

Answer 50

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

Question 51

deuteranomaly

Answer 51

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

Question 52

human tetrachromats

Answer 52

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