L3 - Colour

Question 1

What did Gegenfurtner (2015) say about people, colour and how they perceive the dress?

Answer 1

Those who said the dress was blue and black tended to see darker shades of blue-black in the colour wheel.
Those who saw the dress as white and gold saw more pale blue and Mongolia brown colours.

Question 2

The study by Gegenfurtner (2015) demonstrates what about colour naming?

Answer 2

Seeing the dress in different colours isn’t about colour naming - people are genuinely seeing different colours in the image.

Question 3

Which levels of light are rods used for?

Answer 3

Dim light/night vision

Question 4

Which levels of light are cones used for?

Answer 4

Day vision/colour vision

Question 5

Where is colour processed?

Answer 5

V4 –> V8

Question 6

What would happen if we only had one cone type? (just one of blue, red, green)

Answer 6

We would see everything in colour, but the different colours we perceive would be indistinguishable.

Question 7

What is it called if we only had one cone type/colour?

Answer 7

Cone monochromats

Question 8

What do people with colour blindness have problems with?

Answer 8

Miss tuned cone types, meaning they can’t discriminate between certain colours very well.

Question 9

What is the most common form of colour blindness?

Answer 9

Miss-tuned green cones (deuteranomaly - lack of sensitivity to green light)

Question 10

What are rod monochromats?

Answer 10

People with no cones at all, which leads to huge deficits seeing in daylight.

Question 11

Which colour cones are carried on the X chromosome?

Answer 11

Red and green

Question 12

What is cortical colour blindness?

Answer 12

Damage inflicted to area V8, leading to an inability to discriminate red squares from green squares. (sufferers can still discriminate between lighter squares and darker ones.

Question 13

What information does luminance provide?

Answer 13

Information about clear shapes

Question 14

What information does the blue-yellow channel provide?

Answer 14

Shadows vs sunlight

Question 15

What information does the red-green channel provide?

Answer 15

Red-green colour comparisons

Question 16

Which area is responsible for the conscious perception of colour?

Answer 16

V8

Question 17

What is the difference between colour addition and colour subtraction?

Answer 17

Addition involves the creation of colour through the combination of varying intensities of other colours/light.

Subtraction involves the absorption of different intensities of light

Question 18

What is the problem with adding the blue cone to the yellow in terms of the resulting vision?

Answer 18

Visual acuity is affected detrimentally. Although some differences in colour can now be seen, the detail and acuity of vision decreases.

Question 19

Why is visual acuity lower with yellow and blue cones, compared with yellow cones alone?

Answer 19

Short-wave light (blue-ish colours) is always out of focus in the eye, due to a defect called chromatic aberration.

Question 20

Are there more yellow cones or blue cones in the retina and why?

Answer 20

Yellow - as few blue as possible to avoid further decreases in visual acuity.

Question 21

Which cone type is absent in the fovea of our retinas?

Answer 21

Blue cones.

Question 22

What percentage of blue cones are in our retina?

Answer 22

10%

Question 23

How is luminance created from the output of cones??

Answer 23

Luminance is created from the sum of the activity of red and green cell types.

Question 24

How is red-green colour created from the output of cone types?

Answer 24

Red cone output is divided by green cone output to allow the brain to interpret red-green colour.

Question 25

How is yellow-blue colour created from the output of cone types?

Answer 25

The output of the luminance signal is divided by the output of blue cones.

Question 26

What is opponent coding?

Answer 26

A scheme which encodes colour activation (perceives colour) by comparing the activities of cone types.

Question 27

Where in the LGN has red-green opponency been observed?

Answer 27

Parvocellular layers

Question 28

Which pair of opponent colours may use the konio-cellular pathway?

Answer 28

Blue-yellow

Question 29

What is protanopia?

Answer 29

The total lack of red cones

Question 30

What is deuteranopia?

Answer 30

The total lack of green cones

Question 31

What is tritanopia?

Answer 31

The total lack of blue cones

Question 32

What are anomalous trichromats?

Answer 32

Individuals who have all 3 cones types, but are more/less sensitive than most for one of their cones

Question 33

If you are deuteranomalous, what might the problem be?

Answer 33

That you have all 3 cone types, but have a shifted sensitivity for your green cones.

Question 34

If you have protanomaly, what might the problem be?

Answer 34

That you have all 3 cone types, but have a shifted sensitivity for your red cones.

Question 35

Why is colour constancy important in detecting colours?

Answer 35

Colours are perceived by assessing their wavelengths in comparison to it’s surrounding objects/wavelengths. If colour constancy was not used, any changes in background lighting would change our perception of the colour of an object. We are aware that lighting changes, and account for this by constantly comparing.

Question 36

V1 and V4 can both detect and are activated when green colours are seen. However, only one of them responds to other, non green objects, in a scene when it is bathed in green lighting. Which one is it and why?

Answer 36

V1 activates in response to other elements of the scene, despite the fact they are not green, because it cannot account for the green background. V4, the higher visual area, can account for this by applying colour constancy.

Question 37

V8 may be implicated in __________?

Answer 37

Colour consciousness/ conscious colour processing

Question 38

What is cerebral achromatopsia?

Answer 38

Condition in which sufferers fail to perceive colour - they only see objects in varying shades of grey. This is thought to result from damage to area V8, (or perhaps to a V4-V8 complex), which interprets information from lower visual areas to detect and make sense of colour.