Colour Vision

Question 1

What is the term for normal colour vision?

Answer 1

Trichromacy

Question 2

What are 2 reasons for trichromacy evolution?

Answer 2

• foraging for ripe berries (Regan et al., 2001)
• sociosexual signals from blood oxygenation (Changizi et al., 2006)

Question 3

Name 3 types of dichromacy

Answer 3

• protanopia (lack L)
• deuteranopia (lack M)
• tritanopia (lack S)

Question 4

Name 2 types of anomalous trichromacy

Answer 4

• deuteranomoly (M cone shifted towards L)
• protanomoly (L cone shifted towards M)

Question 5

What is the prevalence of CVD in men and women?

Answer 5

8% in men
<1% in women

Question 6

Mancuso et al. (2009) looked at gene therapy on squirrel monkeys; what did they find and conclude?

Answer 6

• when red opsin gene injected into some cones of dichromatic monkeys, they could see colours they hadn’t previously
• suggests brain can use new signals even though circuitry hadn’t been used.

Question 7

What did Jordan et al. (2010) find about human tetrachromacy?

Answer 7

• Usual 3 cones and one shifted red or green cone
• Only one woman was behaviourally tetrachromatic; suggests cortical processing of the extra signal is not possible

Question 8

Name the 3 cone-opponent channels.

Answer 8

• L/(L+M): “cherry-teal”
• S/(L+M): “violet-lime”
• L+M: achromatic/luminance axis

Question 9

Which cone-opponent channels does each layer of the LGN respond to?

Answer 9

• Parvocellular: cherry-teal
• Koniocellular: violet-lime
• Magnocellular: luminance

Question 10

What adaptation does the lilac chaser illusion show?

Answer 10

Prolonged exposure to a sensory stimulus reduces sensitivity

Question 11

Name 2 theories explaining colour preferences.

Answer 11

• Biological Components Theory
• Ecological Valence Theory

Question 12

What is colour constancy?

Answer 12

The brain’s ability to subtract illumination and recover true surface colour - e.g. The Dress