wk 7 SP

Question 1

What is colour good for?

Answer 1

• Scene segmentation: variations in colour often signal object boundaries
  -Camouflage
  -Perceptual organisation: group elements in a scene

Question 2

how is colour detection a strong evolutionary force ?

Answer 2

Food identification
– Ripe fruit
– Correct leaves
– Harmless or harmful berries
– Poisonous or venomous animals

Question 3

The phenomenon of colour is more complicated than
just wavelength judgement.
* The wavelength of the light reflected only determines
the ____ which is seen.
* Perceived colour is also determined by the:
– _____of the reflected light (how bright it is)
– the ________of the colour (how much white light is mixed
in with the pure hue).

Answer 3

hue
intensity
saturation

Question 4

Difference between blue and red is one of ___

Difference between light and dark blue is one of ______ (usually)

Difference between red and pink is one of _____

Answer 4

hue

intensity

saturation

Question 5

Trichromatic theory (Young - Helmholtz)

Answer 5

3 receptor types which combined responses account for all colours

Blue-sensitive cones maximally responsive to short wavelengths (S-cones)

Green-sensitive cones maximally responsive to medium wavelengths (M-cones)

Red-sensitive cones maximally responsive to long wavelengths (L-cones)

Question 6

Opponent Process Theory
(Hering, Hurvich-Jameson)
3 processes which are opponent in nature:

(colour(

Answer 6

Red-Green
yellow-Blue
Black-White

Question 7

Support for Opponent Process
Theory

Answer 7

(1) Non-existence of certain colours, e.g., bluish-yellow
(2) Colour confusions in colour blindness (red and green)
(3) Complementary afterimages
(4) Colour context effects

Question 8

Trichromacy versus opponent process

Answer 8

Both theories are in fact correct
(a) trichromacy at the level of the cones
(b) opponent processes at the level of LGN
(The Lateral Geniculate Nucleus) and cortical cells.

info from eye to LGN then to cortex

Question 9

opponent process theory. Three diff channels

Answer 9

output of cones is transmitted into three different channels. e.g:

all cones go into brightness channel,

Red and green go into Red-green channel,

Red + Green together (yellow) and then Blue go into Yellow-Blue channel

Wavelengths compared. If more blue than yellow (red + Green), then we perceive blue

Question 10

(4) Colour Blindness

Anopias:

Answer 10

Insensitive to L, M or S wavelengths of light.
(missing a type of cone)

Question 11

(4) Colour Blindness
Anomalies:

Answer 11

Misalignment of L or M in trichromats.
(distribution or deficiency)

Question 12

Protanopia:

cone + prevalence

Answer 12

L-cone pigment missing

1.3% M 0.02% F

Question 13

Deuteranopia:

cone + prevalence

Answer 13

M-cone pigment missing

1.2% M 0.01% F

Question 14

Tritanopia:

cone + prevalence

Answer 14

S-cone pigment missing

0.001% M 0.003% F

Question 15

Anomalies - Anomalous Trichromatism:

protoanomaly:

Answer 15

L-cone pigment deficiency

1.3% M, 0.02% F

(need more red in red-green mix to match yellow)

Question 16

Anomalies - Anomalous Trichromatism:

Deuteranomaly:

Answer 16

M-cone pigment deficiency

5.0% M, 0.35% F

(need more green in red-green mix to match yellow)