Chapter 9

Question 1

What is cerebral achromatopsia?

Answer 1

A loss of colour vision caused by damage to the cortex.

Question 2

What is colour deficiency and when does it typically happen?

Answer 2

people see fewer colors than people with normal color vision.
Usually happens at birth

Question 3

Why it is useful to have colour vision

Answer 3

1. Identify food (red apple is striking)
2. Match food with their correct colours (purple banana would be odd)
3. Match emotions (man with red hue is more likely to be perceived as angry)

Question 4

Explain the newton prism experiment

Answer 4

Light entered through a hole in the window shade and then passed through the prism. The colors of the spectrum were then separated by passing them through holes in a board. Each color of the spectrum then passed through a second prism. Different colors were bent by different amounts. (b) The visible spectrum.

Question 5

What are Chromatic colors?

Answer 5

blue, yellow, red, or green. Happens when all wavelengths are not reflected equally. Called selective reflection.
What are Achromatic colors?
Black, White, and Grey. Reflect all wavelengths equally

Question 6

What are reflectance curves (graph)

Answer 6

A plot showing the percentage of light reflected from an object versus wavelength.

Question 7

How do we have colours for things that are transparent (ex. water)

Answer 7

selective transmission: only some wavelengths pass through the object or substance

Question 8

What is Transmission curves?

Answer 8

plots of the percentage of light transmitted at each wavelength—look similar to the reflectance curves in Figure 9.6, but with percent transmission plotted on the vertical axis

Question 9

What is subtractive color mixture?

Answer 9

when colored paints are mixed together is that when mixed, both paints still absorb the same wavelengths they absorbed when alone, so the only wavelengths reflected are those that are reflected by both paints in common.
Ex. Yellow and blue will only reflect medium because they both share that.

Question 10

What is Additive Color Mixture?

Answer 10

Color mixing with light. Superimposing a blue light and a yellow light creates the perception of white in the area of overlap. This is additive color mixing.

Question 11

What are spectral colors?

Answer 11

Colors that appear in the visible spectrum.

Question 12

What are nonspectral colors?

Answer 12

Colors that do not appear in the spectrum because they are mixtures of other colors. An example is magenta, which is a mixture of red and blue.

Question 13

What are hues?

Answer 13

The experience of a chromatic color, such as red, green, yellow, or blue, or combinations of these colors.

Question 14

What are the other two dimensions of color?

Answer 14

saturation and value (also called lightness).

Question 15

What is Saturation?

Answer 15

The relative amount of whiteness in a chromatic color. The less whiteness a color contains, the more saturated it is.

Question 16

What is Desaturated colours?

Answer 16

Low saturation in chromatic colors as would occur when white is added to a color. For example, pink is not as saturated as red

Question 17

What is Value or lightness?

Answer 17

refers to the light-to-dark dimension of color

Question 18

What is the Munsell color system (funky object)

Answer 18

Depiction of hue, saturation, and value developed by Albert Munsell in the early 1900s in which different hues are arranged around the circumference of a cylinder with perceptually similar hues placed next to each other.
Uses colour solid: A solid in which colors are arranged in an orderly way based on their hue, saturation, and value.

Question 19

What is the trichromacy of color vision?

Answer 19

The idea that our perception of color is determined by the ratio of activity in three receptor mechanisms with different spectral sensitivities. (Proposed by Young) (Also called Young-Helmholtz theory)

Question 20

What is color matching (Supports trichromacy of color vision)?

Answer 20

A procedure in which observers are asked to match the color in one field by mixing two or more lights in another field.

Question 21

What is microspectrophotometry and what was it used for?

Answer 21

direct a narrow beam of light into a single cone receptor.
Caused the discovery of three types of cones in the human retina

Question 22

What is adaptive optical imaging?

Answer 22

A technique that makes it possible to look into a person’s eye and take pictures of the receptor array in the retina.

Question 23

What are Aberrations?

Answer 23

Imperfections on eye’s cornea and lens that distort the light on its way to the retina

Question 24

What is a cone mosaic (picture)?

Answer 24

the cones are colored to distinguish the short-, medium-, and long-wavelength cones. Pretty colours.

Question 25

What is metamerism?

Answer 25

The situation in which two physically different stimuli are perceptually identical. In vision, this refers to two lights with different wavelength distributions that are perceived as having the same color.

Question 26

What are metamers?

Answer 26

Two lights that have different wavelength distributions but are perceptually identical.

Question 27

What is Monochromatism?

Answer 27

Rare form of color blindness in which the absence of cone receptors results in perception only of shades of lightness (white, gray, and black), with no chromatic color present. Monochromats usually have no functioning cones, so their vision is created only by the rods. Can be called colour blind.

Question 28

What is the principle of univariance?

Answer 28

What this means is that a person with only one visual pigment can match any wavelength in the spectrum by adjusting the intensity of any other wavelength and sees all of the wavelengths as shades of gray. Thus, adjusting the intensity appropriately can make the 480-nm and 600-nm lights (or any other wavelengths) look identical

Question 29

What are dichromats?

Answer 29

People with just two types of cone pigment

Question 30

What are trichromats?

Answer 30

People with normal colour vision

Question 31

What are Ishihara plates?

Answer 31

Colour blind test

Question 32

What is unilateral dichromat?

Answer 32

A person who has dichromatic vision in one eye and trichromatic vision in the other eye. People with this condition (which is extremely rare) have been tested to determine what colors dichromats perceive by asking them to compare the perceptions they experience with their dichromatic eye and their trichromatic eye.

Question 33

Name the three major forms of dichromatism (Colourblindness):

Answer 33

Protanopia (protanope is missing the long-wavelength pigment- lack of red), (neutral point: the wavelength at which a dichromat perceives gray.)
Deuteranopia (missing the medium-wavelength pigment “green”)
Tritanopia (short-wavelength pigment “Blue”)

Question 34

What is anomalous trichromatism?

Answer 34

mixes the three wavelengths in different proportions from a trichromat, and an anomalous trichromat is not as good as a trichromat at discriminating between wavelengths that are close together.

Question 35

What is the opponent-process theory of color vision?

Answer 35

A theory originally proposed by Hering, which claimed that our perception of color is determined by the activity of two opponent mechanisms: a blue–yellow mechanism and a red–green mechanism. The responses to the two colors in each mechanism oppose each other, one being an excitatory response and the other an inhibitory response. In addition, this theory also includes a black–white mechanism, which is concerned with the perception of brightness.

Question 36

What Phenomenological evidence was used to support the opponent-process theory of color vision?

Answer 36

color circle - Perceptually similar colors located next to each other and arranged in a circle.
primary colors—red, yellow, green, and blue—and proposed that each of the other colors are made up of combinations of these primary colors. This was demonstrated using a procedure called hue scaling,

Question 37

Why are primary colours called unique hues?

Answer 37

One result was that each of the primaries was “pure.” For example, there is no yellow, blue, or green in the red.

Question 38

Why wasnt opponent-process theory of color vision accepted?

Answer 38

1) trichromatic theory was popular
2) data couldnt compete
3) We didnt know a neural mechanism then that could do that

Question 39

What was the Psychophysical Evidence of opponent-process theory of color vision?

Answer 39

hue cancellation experiments- Procedure in which a subject is shown a monochromatic reference light and is asked to remove, or “cancel,” the one of the colors in the reference light by adding a second wavelength.
Ex. red needs to be added to cancel the perception of greenness.

Question 40

What are opponent neurons?

Answer 40

A neuron that has an excitatory response to wavelengths in one part of the spectrum and an inhibitory response to wavelengths in the other part of the spectrum.
Located in Retina and LGN