Week 2- High level Vision

Question 1

Colour vision depends on how many types of cones

Answer 1

3

Question 2

Colour information is encoded in the retina by

Answer 2

• Midget cells (signalling red-teal differences).

- Small bistratified ganglion cells (signalling lime-violet differences)

Question 3

The genes encoding the Medium and Long photosensitive pigments lie on

Answer 3

The X chromosome

Question 4

Normal trichomats have one copy of

Answer 4

The L photopigment gene followed by one or more copies of the M photopigment gene

Question 5

In dichromacy either the M or the L photopigment gene is

Answer 5

• Missing

- This means the retina only contains 2 types of cone

Question 6

For dichromats colours vary along

Answer 6

One dimension only

Question 7

In anomalous trichromacy, one photopigment gene is

Answer 7

• Hybrid

- Contains sections of M and L photopigment genes

Question 8

In anomalous trichromacy, red-teal signal carried by the midget cells is

Answer 8

• Weaker.
• Because the two cone types provide similar info.
• Red teal colour differences is muted

Question 9

Colour vision depends on

Answer 9

• Bottom up signals

- Higher level perceptual processes

Question 10

The visual system maintains

Answer 10

• Colour constancy

- Object perceived as stable despite changes in the colour of the illumination

Question 11

The light reflected from objects depends on

Answer 11

• The object’s reflectance spectrum

- The illumination spectrum

Question 12

The spectrum of light that falls on the retina is a product of

Answer 12

• The illumination spectrum

- The reflection spectrum

Question 13

The visual system must discover the spectrum of the illuminant to

Answer 13

• Discount it

- This is so that perception can represent the object’s stable reflectance spectrum

Question 14

The ratio law can partly account for

Answer 14

Lightness constancy

Question 15

What’s the Gleb effect

Answer 15

Perceived lightness can flip from white to black once the true luminance of the illumination is known

Question 16

Why don’t objects typically seem smaller when further away

Answer 16

The visual system maintains size constancy

Question 17

Emmert’s law

Answer 17

Perceived size is proportional to the product of retinal image size and perceived distance

Question 18

Bayesian inference

Answer 18

The idea that seeing the expected can be brought into the mathematical framework of Bayes’ theorem

Question 19

Perception depends on both

Answer 19

• ‘bottom up’ signals from the sense organs

- ‘top down’ signals from the brain carrying expectation and context