Chapter 5 Terms Flashcards
A cone that is preferentially sensitive to short wavelengths; colloquially (but not entirely accurately) known as a “blue cone.”
S-cone
A cone that is preferentially sensitive to middle wavelengths; colloquially (but not entirely accurately) known as a “green cone.”
M-cone
A cone that is preferentially sensitive to long wavelengths; colloquially (but not entirely accurately) known
as a “red cone.”
L-cone
The sensitivity of a cell or a device to different wavelengths on the electromagnetic spectrum.
spectral sensitivity
Referring to light intensities that are bright enough to stimulate the cone receptors and bright enough to “saturate” the rod receptors (that is, drive them to their maximum responses).
photopic
Referring to light intensities that are bright enough to stimulate the rod receptors but too dim to stimulate
the cone receptors.
scotopic
The fact that an infinite set of different wavelength-intensity combinations can
elicit exactly the same response from
a single type of photoreceptor. One
photoreceptor type cannot make color
discriminations based on wavelength.
principle of univariance
The theory that the color of any light is defined in our visual system by the relationships of three numbers—the outputs of three receptor types now known to be the three cones. Also called the Young-Helmholtz theory.
trichromacy or trichromatic theory
of color vision
Different mixtures of wavelengths that look identical. More generally, any pair of stimuli that are perceived as identical in spite of physical differences.
metamers
A mixture of lights. If light A and light B are both reflected from a surface to the eye, in the perception of color the effects of those two lights add together.
additive color mixture
A mixture of pigments. If pigments A and B mix, some of the light shining on the surface will be subtracted by A, and some by B. Only the remainder will contribute to the perception of color.
subtractive color mixture
A structure in the thalamus, part of the
midbrain, that receives input from the
retinal ganglion cells and has input and
output connections to the visual cortex.
lateral geniculate nucleus (LGN)
A cell type found in the retina, lateral geniculate nucleus, and visual cortex—that, in effect, subtracts one type of cone input from another.
cone-opponent cell
Referring to cells in the koniocellular layer of the lateral geniculate nucleus of the thalamus. Konio from the Greek for “dust” referring to the appearance of the cells.
koniocellular
Referring to cells in the parvocellular layers of the lateral geniculate nucleus of the thalamus. Parvo from the Greek for “small” referring to the size of the cells.
parvocellular
Referring to stimuli that vary in color but not in luminance.
equiluminant
Referring to the biological
cycle that recurs approximately every
24 hours, even in the absence of cues
to time of day (via light, clocks, etc.).
circadian
A photopigment, found in a class of photoreceptive retinal ganglion cells.
melanopsin
Referring to the middle range of light intensities.
mesopic
The three-dimensional space, established because color perception is based on the outputs of three cone types, that describes the set of all colors.
color space
The theory that perception of color is based on the output of three mechanisms, each of them resulting from an opponency between two colors: red-green, blue-yellow, and black-white.
opponent color theory
Any of four colors that can be described with only a single color term: red, yellow, green, blue. Other colors (e.g., purple or orange) can also be described as compounds (reddish blue, reddish yellow).
unique hue
An inability to perceive colors that is caused by damage to the central nervous system.
achromatopsia
Color words that are single words (like “blue,” not “sky blue”), are used with high frequency, and have meanings that are agreed upon by speakers of a language.
basic color terms
In sensation and perception, the idea
that basic perceptual experiences (e.g., color perception) may be determined in part by the cultural environment.
cultural relativism
In philosophy, a private conscious experience of sensation or
perception.
qualia
Referring to the rare situation (in humans, at least) where the color of any light is defined by the relationships of four numbers—the outputs of those four receptor types.
tetrachromatic
An individual who suffers from color blindness that is due to the absence of M-cones.
deuteranope
An individual who suffers from color blindness that is due to the
absence of L-cones.
protanope
An individual who suffers from color blindness that is due to the
absence of S-cones.
tritanope
A better term for the commonly used term color-blind. Most “color-blind” individuals can still make discriminations based on wavelength. Those discriminations are different from the norm—that is, anomalous.
color-anomalous
An individual with only one cone type. These individuals are truly color-blind.
cone monochromat
An individual with no cones of any type. In addition to being truly color-blind, rod monochromats are badly visually impaired in bright light.
rod monochromat
A failure to recognize objects in spite of the ability to see them. Typically due to brain damage.
agnosia
An inability to name objects in spite of the ability to see and recognize them (as shown by usage). Typically due to brain damage.
anomia
