Color Vision

Question 1

3 steps to color perception and definitions

Answer 1

detection
- must be able to sense light in the first place

discrimination
- must be bale to differentiate between different wavelengths or mixtures of them (ex. bar of light vs. edge)

appearance
- we assign perceived colors to different objects in the world and assume such colors are stable, even if the overall lighting changes

Question 2

3 types of opsins for cones

Answer 2

short: blue range

medium: green range

long: red range

Question 3

opsins

Answer 3

what wavelengths the eye responds to
- dictate their color sensitivity

Question 4

what two cones are close to each other in wavelength?

Answer 4

medium and long/green and red!

Question 5

opsin type for rods

Answer 5

rhodopsin; not full color

Question 6

scotopic vision is __________ (what does this mean?)

Answer 6

univariate

• in scotopic conditions, rods work alone meaning all color processing is translated into 1 response
• lots of variables into 1

Question 7

why is color vision so bad at night?

Answer 7

because scotopic vision is univariate but also trying to process infinite color (which cannot be fully processed by rods)

Question 8

rods all respond the same to _____, with a ______ response

Answer 8

color; graded (meaning colors on either side produce a similar response)

Question 9

trichromatic theory of color vision

Answer 9

any light perception in human vision is dictated by combining 3 variables (S,M,L) - aka the Young-Helmholtz Theory

Question 10

metamers

Answer 10

different mixtures of light that are perceived as identical, despite having different generators

items look the same in given light but are actually different shades

Question 11

while not univariate, cones still end up coming to the same consensus for different color combinations, meaning

Answer 11

visual system comes to a decision/compromise at what it is seeing

Question 12

when red and green/long and medium wavelengths are fired in the cones, this creates the perception of what color?

Answer 12

yellow!

Question 13

what study showed that light is additive?

Answer 13

maxwell’s color matching experiment

Question 14

light is _____ while paint is ______

Answer 14

additive; subtractive

Question 15

3 factors of color and definitions

Answer 15

hue - the color (RGB)

saturation - the strength of the hue (aka the distance from white)

brightness - the distance from black

Question 16

four unique hues

Answer 16

a color that has no hint of another primary color in it

4 main colors: red, yellow, green, blue

yellow and blue don’t mix while red and green don’t mix

Question 17

how to test unique hues?

Answer 17

cancelling colors

adding blue to yellow until it contains neither blue nor yellow, only green

Question 18

main takeaway of color canceling with four unique hues

Answer 18

result in 2 spectrums:

yellow-blue
green-red

Question 19

cone opponent cells

Answer 19

cells that track the difference in output between sets of cones

Question 20

example of concentric double-opponent cone cell

Answer 20

red inside with green border then green outside with red border

Question 21

example of single-opponent cone cell

Answer 21

red inside with green outside

Question 22

achromatopsia

Answer 22

brain derived full color vision loss

Question 23

3 opponent mechanisms for cones

Answer 23

red-green
yellow-blue
white-black

Question 24

negative afterimages for opponent processing

Answer 24

can see the image still but in opposite colors

light –> dark
red –> green
blue –> yellow

Question 25

color contrast

Answer 25

perceptual effect where the same color appears different when paired with a similar or an opponent color

ex) the center squares appear differently depending on their surround

Question 26

color assimilation

Answer 26

perceptual effect where colors “bleed” into each other, each taking on some of the chromatic quality of the other

ex) pointillism!

Question 27

color constancy

Answer 27

generally, despite lots of changes in overall lighting, we perceive a given object as the same color

Question 28

what do we discount with color constancy

Answer 28

the illuminant
- the light itself hitting an object’s surface

Question 29

what do we assume with color constancy

Answer 29

broadband light
- entire visible spectrum

assume the surfaces are broadband too and reflect most wavelengths

Question 30

example of color constancy

Answer 30

the dress from 2015!

the illuminant
- blue light source = white stripe
- yellow light source = blue stripe!

also depends on mental reference

Question 31

cultural relativism

Answer 31

idea that basic perceptual experiences (e.g., color perception) may be determined in part by the cultural environment

Question 32

color-anomalous

Answer 32

not fully color blind; perception of wavelengths altered

Question 33

color-anomalous types

Answer 33

deuteranope
- due to absence of M-cones “green”

protanope
- due to absence of L-cones “red”
^^both similar^^

tritanope
- due to absence of S-cones “blue”

cone monochromat
- only 1 cone type; truly color-blind

rod monochromat
- no cones of any type; truly color-blind and very visually impaired in bright light

Question 34

color is tied to lots of other _________

Answer 34

processing/senses

Question 35

synesthesia

Answer 35

when one stimulus evokes the experience of another stimulus that is not present

ex) hear music but see colors because of it!

Question 36

This theory of color vision suggests all light perception can be broken down into combinations of 3 colors:

a) Opponent Process Theory
b) Trichromatic Color Theory
c) Color Contrast Theory
d) Color Constancy Theory

Answer 36

B

Question 37

A “single opponent” cell in LGN is found to have a S+
(Blue) center receptive field. What would we most likely label its surround?

a) L- (Red)
b) M- (Green)
c) S- (Blue)
d) L-/M- (Red+Green)

Answer 37

D; red+green make yellow = blue-yellow opponent processing

Question 38

Juan conducts an experiment wherein he has participants stare at colored dots, and then after awhile has them look at a gray set of dots, resulting in them seeing the opposite colors. What technique is Juan using?

a) Selective adaptation
b) The method of limits
c) Color mixing
d) Illuminant discounting

Answer 38

A