Chapter 9 Flashcards Preview

Sensation and Perception > Chapter 9 > Flashcards

Flashcards in Chapter 9 Deck (64):
1

3 Functions of color vision

  1. Object recognition
  2. Signals (natural or man made)
  3. Detection (evolutionary)

2

Describe the relationship between color and object identification

    We recognize objects that are the right color faster and more accurately

3

What colors do color researchers consider to be pure or unique colors?

Red, yellow, green, and blue

4

Pure colors in order of shortest to longest wavelengths

Blues

Greens

Reds and yellows

5

How many colors can people discriminate between across the visual spectrum

about 200

6

saturation

the amount of whiteness in a chromatic color

7

Range of wavelengths in visual spectrum

400nm - 700nm

8

Chromatic colors

Hues

Occurs when some wavelengths are reflected more than others

9

Achromatic colors

white, gray, black

Occur when light is reflected equally across the spectrum

10

Selective reflection

when an object reflects some wavelengths more than others

11

Reflectance curves

plots of the percentage of light reflected vs. wavelength

12

Selective transmission

When some wavelengths pass through transparent objects or liquids more than others

13

Blue light + yellow light

Why

White

Short wavelengths + medium and long wavelengths

14

Additive color mixture

Light mixing

All the wavelengths of the lights are added up when they are superimposed upon each other

15

subtractive color mixture

paint mixture

The paints still absorb the same wavelengths they would alone, so the only lengths that are reflected are the ones they reflect in common

16

What is necessary to get a new color mixing paints (instead of black)

The colors need to both reflect some light that is in a similar part of the spectrum

17

trichromatic theory of color vision

color vision relies of activity for three different receptor mechanisms with different spectral sensitivities

 

18

How did Hemholtz and Young test their trichromatic theory?

color-matching experiments

subjects adjusted amounts of three different wavelengths of light until it matched the test color

19

2 Key findings of Young and Hemholtz color matching experiments

  1. 3 wavelengths could match any test color (as long as any of them couldn't be made using the other two)
  2. People couldn't match all wavelengths with just two colors

 

20

Another name for the trichromatic theory

Young-Hemholtz theory of color vision

21

What causes the differences in spectral sensitivity between cones?

Differences in the structure of the opsin protein (which is connected to the retinal)

22

metamerism

when two physically different stimuli are perceptually identical

23

metamers

2 lights with different wavelength distributions are perceptually the same

24

principle of univariance

once a photon of light is absorbed by a visual pigment molecule the identity of the light's wavelength is lost

25

How does the nervous system tell the difference between two wavelengths of light regardless of light intensity?

With ratio information

Ratio of responses of two pigments to two wavelengths (One light causes a large response from one pigment and a smaller response from another)

Ratios remain constant

26

trichromats

people with three visual pigments

27

color deficiency

see fewer colors in the spectrum

problems in receptors in the retina

28

Ishihara plates

color deficiency tests

circles from Little Miss Sunshine

29

monochromat

# of pigments

visual spectrum

how many wavelengths needed to match

one pigment

shades of gray

needs only one wavelength to match any other color in the spectrum

 

30

dichromat

two pigments

only needs two wavelengths to match the others in the spectrum

31

anomalous trichromat (vs a regular trichromat)

needs 3 wavelengths to match any other wavelength

but

mixes these into different proportions

not as good at discriminating between wavelengths that are close in color 

32

unilateral dichromat

trichromatic vision in one eye and dichromatic in the other

33

Monochromats: rods vs. cones

Usually have no cones - all rods

Poor visual acuity

Sensitive to bright lights

34

3 types of dichromats

protanopia

deuteranopia

tritanopia

35

two most common types of dichromats and how are they inherited

protanopia and deuteranopia

X chromosome

36

How many normal genes are required for normal color vision

Just one

thats why females are less likely to have color issues

37

Protanopia

No long wavelength cones

short wavelengths look blue

long yellow

neutral point: 492

38

deuteranopia

No medium wavelength cones

short wavelengths - blue

long - yellow

neutral point: 498

39

tritanopia

no short wavelength cones

blue - short wavelengths

red - longwavelengths

neutral point: 570nm

40

why do anomalous tetrachromats match colors differently?

their M and L pigment spectra have been shifted to be closer together

41

How are the signals from the S, M, and L receptors transmitted to the brain?

Information about the difference between pairs of signals is sent, not based on different sized signals

42

Two theories of color vision

trichromatic theory

opponent-process theory

43

opponent-process theory

color vision is caused by opposing responses that are generated by blue and yellow and by red and green

44

How did Hering study opponent process theory

afterimages

45

simultaneous color contrast

when surrounding an area with a color changes the appearance of the surrounded area

46

opponent neuron

has an excitatory response to light from one part of spectrum and inhibitory response from another

(B/W; R/G; B/Y)

47

Stages of color processing

  1. Receptors respond with different patterns to different wavelengths
  2. neurons receive the inhibitory and excitatory signals from the receptors

 

48

cerebral achromatopsia

damage to the cortex that causes a loss of color vision

49

Is there a single color center in the brain?

It is likely that color perception is caused by activity in many areas that respond to many qualities

50

two types of opponent neurons found in the cortex

single-opponent neurons

double-opponent neurons

51

single vs. double opponent neuron receptive fields

single: center surround

double: side by side

52

How may functioning differ between single/double opponent neurons

single: important for perceiving color within a region

double: important for perceiving boundaries

53

color constancy

we perceive colors of things as being relatively constant even under different levels of illumination

54

chromatic adaptation

exposure to light in a specific part of the visual spectrum

can cause a decrease in sensitivity to light from the area that was [resented

55

When does color constancy work the best

When an object is surrounded by things of many different colors

Loses its effect when seen in isolation

56

memory color

the characteristic color of an object influences our perception of that object

57

lightness

perception of shades from white to black

58

lightness constancy

we see whites, grays, and blacks as staying about the same shade under different illuminations

59

reflectance

the proportion of the light that is striking a surface that is reflected into our eyes

60

What does our perception of an object's lightness rely on

the percentage of light reflected from the object, regardless of illumination

61

ratio principle

with even illumination, lightness is determined by the ratio of reflectance of the object to the reflectance of surrounding objects

62

reflectance edge

edge where the reflectance of two surfaces changes

63

illumination edge

edge where the lighting changes

64

How does visual system account for illumination vs. reflectance?

  1. Shadow's shape
  2. Penumbra
  3. Orientation of the surfaces