wk 7 SP Flashcards

colour vision

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1
Q

What is colour good for?

A
  • Scene segmentation: variations in colour often signal object boundaries
    -Camouflage
    -Perceptual organisation: group elements in a scene
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2
Q

how is colour detection a strong evolutionary force ?

A

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

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3
Q

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).

A

hue
intensity
saturation

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4
Q

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 _____

A

hue

intensity

saturation

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5
Q

Trichromatic theory (Young - Helmholtz)

A

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)

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6
Q

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

(colour(

A

Red-Green
yellow-Blue
Black-White

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7
Q

Support for Opponent Process
Theory

A

(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

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8
Q

Trichromacy versus opponent process

A

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

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9
Q

opponent process theory. Three diff channels

A

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

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10
Q

(4) Colour Blindness

Anopias:

A

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

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11
Q

(4) Colour Blindness
Anomalies:

A

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

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12
Q

Protanopia:

cone + prevalence

A

L-cone pigment missing

1.3% M 0.02% F

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13
Q

Deuteranopia:

cone + prevalence

A

M-cone pigment missing

1.2% M 0.01% F

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14
Q

Tritanopia:

cone + prevalence

A

S-cone pigment missing

0.001% M 0.003% F

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15
Q

Anomalies - Anomalous Trichromatism:

protoanomaly:

A

L-cone pigment deficiency

1.3% M, 0.02% F

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

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16
Q

Anomalies - Anomalous Trichromatism:

Deuteranomaly:

A

M-cone pigment deficiency

5.0% M, 0.35% F

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