Colour Perception Flashcards Preview

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Flashcards in Colour Perception Deck (20)
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1

Importance of being able to identify colours

Evolution - patterns indicate danger
Detecting predators
Self expression
Identifying objects and people
Culture

2

The visible spectrum

There is an electromagnetic spectrum from short wavelengths to long - small section of visible light (400- to 800 metres)
Some species have infared (warmth) or ultraviolet vision

3

What are humans known as?

Trichromats - having 3 cones, short, long and medium

4

What colour is the long wavelength?

Yellow/red

5

What colour is the medium wavelength?

Green

6

What colour is the short wavelength?

Blue

7

What is the evolution of our cones?

Most of our primates are dichromatic, but now we have 3

8

Why have we evolved to have 3 cones?

Splitting a yellow cone to one that's medium and long enables us to see red/green differences and can detect blood flow under species skin
Trichromats have the most bare skin on show so need to see changes in blood, indicates health

9

What is the genetic deficiency of cones?

Dichromats - 2 cones
Monochromats - 1 cone
Anomolous

10

Are cone deficiency nature or nuture?

Both
Males are more likely to get it then females
but sometimes acquired, ageing, drugs and hormones

11

Types of dichromats

Protanopia - lacking red, long cone
Deuteranopia - lacking green - medium
Tritanopia - lacking blue, short

12

Types of anomolous

Deuteranomoloy - medium and long wavelength overlap
Protanomoly - long overlaps to medium

13

A cure for genetic deficiency?

Gene therapy on cones on a monkey meant it could see colours it couldn't see before, brain uses new signal

14

What is human tecrachromacy?

Having 4 cones, 3 normal and shifted red or green
Psychophysical tests - anomaloscope
14 woman, only 1 was behaviourally different
Retina has 4 times but there is lots of machinery in place to use the signal so not everyone will make full use

15

What is cone opponency?

The output of 3 cones is combined to give 3 channels. Colour will fall along an axis:
Red-green - cherry teal LM - parvocellular
Blue-yellow - lime violet, S, konicellular
Black-white - achromatic, magnocellular

16

What is an example of cone opponency?

Colour after effects

17

Where is colour at the cortex?

There are patches of blobs responsible for colour at the cortex (V1) but there are other areas as well V2, V4, V8
Sent to temporal cortex (ventral)
Receives colours in circular ways

18

Why do we prefer some colours?

Biological components theory - we prefer colours that stimulate our visual system
Ecological valence theory - preference is due to colour object associations e.g. we like blue as it associates with the sky

19

Top down effects

Memory of colour influences perception of colour
eg. colour remembered more saturated than they are
If asked to make banana grey, ppts make it blue because blue is opposite to yellow

20

Cerebral achomatopsia

Damage to cortical area, lose colour
Humans with lesions in V4, V8
Functioning cones but things don't appear coloured, can affect one visual field only - shows importance of cortex