Cognitive Psychology - Colour

What is Colour Used for?

• Recognition

• Health/Food

• Mating

Where does Colour come from?

Visible Light

Cone Photoreceptors present in Trichromacy

• Short wavelength cone (violet/blue)

• Middle wavelength cone (green)

• Long wavelength cone (red)

Evolutionary Reason for Trichromacy

Foraging for fruit and berries

Dichromacy

Where only Short and Long Photoreceptors are present

What do trichromatic animals tend to have?

More colourful skin/fur

Types of Dichromacy

Red-Green Colour Blindness:

• Protanopia (No long wavelength cone - struggles to see red light)

• Deuteranopia (No medium wavelength cone - struggles to see green light)

Blue-Yellow Colour Blindness:

• Tritanopia  (No short wavelength cone)

Types of Anomalous Trichromacy

• Deuteranomaly (M cone shifts to L)

• Protanomaly (L cone shifts to M)

Gender Differences in presence of CVD

• Men: 8%

• Women: 1%

How can Gene Therapy be used to change Dichromats → Trichromats?

Red Opsin Gene injected into cones, causing dichromatic male squirrel monkeys to become trichromatic.

Evidence of Tetrachromacy

Some women have 4 cones (3 + shifted red or green cone)

Cone Opponency

 

Where output from three cones are combined and contrasted to give three cone opponent channels.

Examples of Cone Opponency

 

• Signal from L cone compared with /(L+M) cherry-teal

• Signal from S cone compared with /(S+M) violet-lime

• L+M: achromatic

Colour Memory

Theory that some objects have a typical colour that we learn from experience and that there is an aesthetic response to colour.

Ecological Valance Theory

Theory suggesting we prefer certain colours due to colour associations (blue is good because of water, off-green is bad because rotten)

What might colour preference be influenced by?

Culture

Evidence of Colour Constancy

Purves and Lotto (2002) colour cube: Illusion where blue and yellow tiles are the same colour but appear different due to the background.