psych of perception chapter 9

Question 1

saturation

Answer 1

changing the intensity to make colours brighter or dimmer, or by adding white to change a colour’s saturation

Question 2

reflectance curves

Answer 2

plots of the percentage of light reflected versus wavelength - for a number of objects

Question 3

chromatic colours / hues

Answer 3

when some wavelengths are reflected more than other - as for the colored paints and the tomato

Question 4

selective reflection

Answer 4

this property of reflecting some wavelengths more than others, which is a characteristic of chromatic colours, is called selective reflection

Question 5

achromatic colours

Answer 5

when light reflection is similar across the full spectrum - that is, contains no hue - as in white, black, and all the grays between these two extremes, we call these colors achromatic colors

Question 6

selective transimmission

Answer 6

in the case of things that are transparent, such as liquids, plastics, and glass, chromatic colour is created by selective transmission, meaning that only some wavelengths pass through the object or substance

Question 7

additive color mixture

Answer 7

mixing lights involves adding up the wavelengths of each light in the mixture, mixing lights is called additive color mixture

Question 8

what happens when coloured lights are superimposed?

Answer 8

all of the light that is reflected from the surface by each light when alone is also reflected when the lights are superimposed

Question 9

what happens when coloured paints are mixed?

Answer 9

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

Question 10

subtractive colour mixture

Answer 10

each blob of paint absorbs wavelengths and these wavelengths are still absorbed by the mixture, mixing paints is called subtractive color mixture. The blue and yellow blobs subtract all of the wavelengths except some that are associated with green.

Question 11

mixing lights vs mixing colours

Answer 11

Mixing lights causes more wavelengths to be reflected (each light adds wavelengths to the mixture); mixing paints causes fewer wavelengths to be reflected (each paint subtracts wavelengths from the mixture)

Question 12

trichromatic theory of colour vision

Answer 12

states that colour vision depends on the activity of three different receptor mechanisms
this theory relies only on the retinal level

Question 13

color-matching experiments

Answer 13

observers adjusted the amounts of three different wavelengths of light mixed together in a “comparison field” until the colour of this mixture matched the colour of a single wavelength in a “test field.”

Question 14

Young-Helmholtz theory of color vision

Answer 14

idea of the theory is that colour vision depends on three receptor mechanisms, each with different spectral sensitivities
- according to this theory, light of a particular wavelength stimulates the three receptor mechanisms to different degrees, and the pattern of activity in the three mechanisms results in the perception of a colour

Question 15

cone pigments

Answer 15

all visual pigments are made up of a large protein component called opsin and a small light-sensitive component called retinal. Differences in the structure of the long opsin part of the pigments are responsible for the three different absorption spectra

Question 16

matamerism

Answer 16

two physically different stimuli are perceptually identical

Question 17

metamers

Answer 17

two identical fields in a colour-matching experiment are called metamers

Question 18

trichromats

Answer 18

people with three visual pigments

Question 19

colour deficiency

Answer 19

most problems with colour vision involve only a partial loss of colour perception, called colour deficiency, and are associated with problems with the receptors in the retina

Question 20

Isihihara plates

Answer 20

colour vision test (colour vision plates) for detection of red-green colour deficiencies

Question 21

monochromat

Answer 21

monochromat can match any wavelength in the spectrum by adjusting the intensity of any other wavelength. Thus, a monochromat needs only one wavelength to match any colour in the spectrum and sees only in shades of grey

Question 22

dichromat

Answer 22

dichromat needs only two wavelengths to match all other wavelengths in the spectrum

Question 23

anomalous trichromat

Answer 23

anomalous trichromat needs three wavelengths to match any wavelength, just as a normal trichromat does. However, the anomalous trichromat mixes these 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 24

unilateral dichromat

Answer 24

person with trichromatic vision in one eye and dichromatic vision in the other

Question 25

colour-blind

Answer 25

monochromats see everything in shades of lightness (white, grey, and black) and can therefore be called colour-blind (as opposed to dichromats, who see some chromatic colours and therefore should be called colour deficient)

Question 26

simultaneous colour contrast

Answer 26

background of object can affect colour perception

Question 27

principle of univariance

Answer 27

absorption of a photon causes the same effect no matter what the wavelength
whatever colours you are perceiving it is coming from the number of photons

Question 28

monochromat

Answer 28

just one type of pigment (total colour blind)
can see brightness of shades of grey

Question 29

dichromat

Answer 29

two types of pigment (partially colour blind, weak colour perception)
can see chromatic colours, but cannot distinguish among all colours

Question 30

trichromat

Answer 30

three types of pigment (normal colour vision)
can discriminate among more wavelengths across spectrum

Question 31

opponent-process theory of colour vision

Answer 31

this theory states that colour vision is caused by opposing responses generated by blue and yellow and by red and green

Question 32

behavioural evidence for opponent-process theory of colour vision

Answer 32

• colour afterimages and simultaneous colour contrast show the opposing pairings
• types of colour blindness are red/green and blue/yellow

Question 33

colour constancy

Answer 33

perception of colours as relatively constant despite changing light sources

Question 34

chromatic adaptation occurs when

Answer 34

occurs when prolonged exposure to chromatic colour leads to receptors:
* “Adapting” when the stimulus colour selectively bleaches a specific cone pigment
* Decreasing in sensitivity to the colour

Question 35

perception of lightness

Answer 35

• is not related to the AMOUNT of light reflected by the object
• is related to the PERCENTAGE of light reflected by an object
  RATIO

Question 36

reflectance edges

Answer 36

edges where the amount of light reflected changes between two surfaces

Question 37

illumination edges

Answer 37

edges where lighting of two surfaces changes