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PSYB51 ch.5
chapter 5
| Question | Answer |
|---|---|
| Problem of unvariance | fact that an infinite set of different wavelength-- intensity combinations can elicit exactly the SAME response frm a SINGLE type of photoreceptor. 1 photoreceptor type can't make color discriminations based on wavelength |
| scotopic | light intensities that are bright enough to stimulate the rod receptors but too dim to stimulate the cone receptors |
| photopic | light intensities that are bright enough to stimulate the cone receptors & “saturate” the rod receptors (i.e. Drive them to their max. responses |
| S-cone | cone that is preferentially sensitive to SHORT wavelengths; known as (but not entirely) as a “blue cone” |
| M-cone | cone that is preferentially sensitive to MIDDLE wavelengths; known as (but not entirely) as a “green cone” |
| L-cone | cone that is preferentially sensitive to LONG wavelengths; known as (but not entirely) as a “red cone” |
| trichromatic theory of color vision (trichromacy or Young Helmholtz theory) | theory that the color of any light is defined in our visual system by the relationships of 3 numbers, the outputs of 3 receptor types known as cones |
| metamers | different mixtures of wavelengths that look identical. More generally any pair of stimuli that are perceived as identical in spite of physical differences (eg. Red + green, or just yellow) |
| additive color mixture | mixture of LIGHTS (see p.110) |
| subtractive color mixture | mixture of PIGMENTS (see p.110) |
| color space | 3-D space, estd. B/c colour perception is based on the outputs of 3 cone types, that describes the sets of all colours |
| hue | chromatic (colouful) aspect of colour (red, blue, green, yellow, & so on) |
| saturation | chromatic strength of a hue. White has “0” saturation, pink is more saturated and red is fully saturated |
| brightness | the distance frm black (zero brightness) in color space |
| LGN | structure in the thalamus, part of the midbrain, that receives input frm retinal ganglion cells, & has input & output connections to the visual cortex |
| color-opponent cell | neuron whose output is based on a difference b/w sets of cones |
| opponent color-theory | theory that perception of colour is based on the output of 3 mechanisms., each 1 of them based on an opponency b/w 2 colors: red-green, blue-yellow, & black-white |
| unique blue | a blue that has no red or green tint |
| unique hue | any 4 colors that can be described w/only a single color term: red, yellow, blue, green. Other colours (s/a purple or orange) can be described as compunds (reddish blue, reddish yellow) |
| afterimage | visual image seen after the stimulus has been removed due to opponent colours |
| adapting stimulus | stimulus whose removal produces a change in visual perception or sensitivity |
| negative afterimage | afterimage whose polarity is the opposite of the original stimulus. Light stimuli produce neg afterimages. Colors are complementary; eg. Red produces green; yellow produces blue |
| neutral point | point @ which an opponent color mechanism is generating no signal. If red-green & blue-yellow mechanisms are @ their neutral points, a stimulus will appear achromatic. (black-white process has no neutral point) |
| achromatopsia | inability to perceive colours that is caused by damage to the CNS |
| deuteranope | an individual who suffers frm color blindness that is due to the absence of M-cones |
| protanope | an individual who suffers from color blindness that is due to the absence of L-cones |
| tritanope | an individual who suffers from color blindness that is due to the absence of S-cones |
| color anamalous | better term for the color blind b/c most color-blind individuals can still make discriminations based on wavelength that are different from normal |
| cone monochromat | an individual w/only one cone type. Cone monochromatics are truly color-blind; see only shades of grey |
| rod monochromat | an individual w/no cones of any type. Color blind but are badly visually impaired in bright light |
| agnosia | faliure to recognize objects in spite of the ability to see them. Agnosia typically due to brain damage |
| anomia | inability to name objects in spite of the ability to see & recognize them (as shown by usage). Anomia is a type of brain damage |
| cultural relativism | in sensation & perception, the idea that basic perceptual experiences (eg. Color perception) may be determined in part by the cultural environment |
| unrelated color | a color that can be experienced in isolation |
| related color | a color s/a brown or grey that is seen only in relation to other colours. |
| Illuminant | the light that illuminates a surface |
| spectral reflectance function | function relating the wavelength of light to the percentage of that wavelength that is reflected frm a surface |
| spectral power distribution | physical energy in light as a function of wavelength |
| color constancy | the tendency of a surface to appear the same color under a fairly wide range of illuminants |
| reflectance | the percentage of light hitting a surface that is not reflected & not absorbed into the surface. Typically reflectance is given as a function of wavelength |
Created by:
Ugly.Beauty