6.1.1 Visual Coding 2

Question 1

Visible light consist of ____ ____ within the range from less than 400 nm to more than 700 nm.

Answer 1

electromagnetic radiation

Question 2

We perceive the shortest visible wavelength as ____.

Answer 2

violet

Question 3

Progressively longer wavelengths are perceived as ____, ____, ____, ____, and ____.

Answer 3

blue, green, yellow, orange, and red

Question 4

We call these ____ “light” only because the receptors in our eyes are turned to detect them.

Answer 4

wavelengths

Question 5

____ ____ (shorter wavelengths) are not seen by humans, however, many species of birds, fish, and insects have visual receptors sensitive to shorter wavelengths.

Answer 5

Ultraviolet radiation

Question 6

Thomas Young proposed that we perceive colour by ____ the responses across a few types of receptors, each of which was sensitive to a different range of wavelengths.

Answer 6

comparing

Question 7

This theory of receptor comparison, later modified by Hermann Helmholtz, is known as the ____ ____ of colour vision, or the Young-Helmholtz theory.

Answer 7

trichromatic theory

Question 8

According to this trichromatic theory, we perceive ____ through the relative rates of response by three kinds of cones, each one maximally sensitive to a different set of wavelengths. (Trichromatic means three colours)

Answer 8

colour

Question 9

Helmholtz found that people could match any colour by mixing appropriate amounts of just three wavelengths. Therefore, he concluded that three kinds of receptors – we now call them cones – are sufficient to account for human ____ ____.

Answer 9

colour vision

Question 10

According to the trichromatic theory, we discriminate among wavelengths by the ____ of ____ across the three types of cones.

Answer 10

ratio of activity

Question 11

Cones is come in ____ wavelength types: short-wavelength, medium-wavelength, and long-wavelength.

Answer 11

three

Question 12

Given the desirability of seeing all colours in all locations, we might suppose that the three kinds of cones would be evenly abundant and evenly distributed. In fact, they are not. ____ and ____ wavelength cones are far more abundant than short wavelength cones.

Answer 12

Long and medium

Question 13

Although the ____ wavelength cones are about evenly distributed across the retina, the other two kinds are distributed haphazardly, with big differences among individuals.

Answer 13

short

Question 14

In the retinas periphery, cones are so scarce that you have no useful ____ ____.

Answer 14

colour vision

Question 15

The ____ ____ is the part of the world that you see.

Answer 15

visual field

Question 16

The trichromatic theory is ____ as a theory for colour vision. It cannot account for negative colour after images.

Answer 16

incomplete

Question 17

Edward Herring, a 19th century physiologist, proposed the ____ ____ ____.

Answer 17

opponent process theory

Question 18

The opponent process theory is, the brain has a mechanism that perceives colour on a continuum from ___ to ___, another from ___ to ___, and another from ___ to ___.

Answer 18

red to green, yellow to blue, white to black

Question 19

If light stimulates a cell long enough, the cell becomes fatigued. If we now remove the light, the cell responds less than its baseline level, and therefore produces an experience of an opposite colour. This is a special kind of coding, in which an increase in response produces one ____, and a decrease produces a different ____.

Answer 19

perception

Question 20

However, after-images depend on the whole context, not just the light on individual receptors. The ____ ____ must be responsible, not the bipolar or ganglion cells.

Answer 20

cerebral cortex

Question 21

The trichromatic theory and the opponent-process theory cannot easily explain ____ ____, the ability to recognise colours despite changes in lighting.

Answer 21

colour constancy

Question 22

Our perception of the ____ of an object requires comparing it with other objects.

Answer 22

brightness

Question 23

To account for colour and brightness constancy, Edwin Land proposed the ____ ____ (a combination of the words retina and cortex): the cortex compares information from various parts of the retina to determine the brightness and colour for each area.

Answer 23

retinex theory

Question 24

Whenever we see anything, we make an ____. That is, visual perception requires a reasoning process, not just retinal stimulation.

Answer 24

inference

Question 25

____ ____ ____ is also know as colourblindness.

Answer 25

Colour vision deficiency

Question 26

Before colour vision deficiency was discovered in the 1600s, people assumed that vision ____ the objects we see. They assumed that everyone saw objects the same way.

Answer 26

copies

Question 27

Investigators discovered that it is possible to have otherwise satisfactory vision without seeing colour. That is, colour depends on what our ____ do with incoming light, it is not a property of the light itself.

Answer 27

brains

Question 28

In red-green colour deficiency, the most common form of colour deficiency, people have trouble distinguishing red from green because the long- and medium-wavelength cones have the same ____ instead of different ones.

Answer 28

photopigment

Question 29

The gene causing red-green colour deficiency is on the ____. About 8% of men are red-green colourblind compared with less than 1% of women.

Answer 29

X chromazone