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level: Colour Vision

Questions and Answers List

level questions: Colour Vision

Question	Answer
An inability to perceive colours that is caused by damage to the central nervous system	Achromatopsia
A stimulus whose removal produces a change in visual perception or sensitivity	Adapting stimulus
A mixture of lights. If light A and light B are both reflected from a surface to the eye, in the perception of colour the effects of those two lights add together	Additive colour mixture
A failure to recognise objects in spite of the ability to see them. This is typically due to brain damage	Agnosia
An inability to name objects in spits of the ability to see and recognise them (as shown by usage). Typically due to brain damage	Anomia
Colour words that are single words (blue - not sky blue) are used with high frequency and have meanings that are agreed upon by speakers of a language	Basic colour terms
Referring to the biological cycle that recurs approximately ever 24 hours, even in the absence of cues to time of day	Circadian
A colour perception effect in which two colours bleed into each other, each taking on some of the chromatic quality of the other	Colour assimilation
The tendency of a surface to appear the same colour under a fairly wide range of illuminants	Colour constancy
A colour perception effect in which the colour of one region induces the opponent colour in a neighbouring region	Colour contrast
, The three-dimensional space, established because colour perception is based on the outputs of three cone types, that describes the set of all colours	Colour Space
A better term for the commonly used term colour-blind. Most colour-blind individuals can still make discriminations based on wavelength. Those discriminations are different from the norm.	Color-anomalous
An individual with only one cone type. Cone monochromats are truly colour-blind	Cone monochromat
A cell type - found in the retina, lateral geniculate nucleus, and visual cortex - that, in effect, subtracts one type of cone input from the other	Cone-opponent cell
In sensation and perception, the idea that basic perceptual experiences may be determined in part by the cultural environment	Cultural relativism
An individual who suffers from colour-blindness that is due to the absence of M-cones	Deuteranope
Referring to stimuli that vary in colour but not in luminance	Equiluminant
the light that illuminates a surface	Illuminant
Referring to cells in the koniocelluar layer of the lateral geniculate nucleus of the thalamus. From the Greek for 'dust' referring to the appearance of the cells	Koniocellular
A cone that is preferentially sensitive to long wavelengths; colloquially known as a 'red cone'.	L-cone
A cone that is preferentially sensitive to middle wavelengths; colloquially known as a 'green cone'.	M-cone
Referring to the middle range of light intensities	Mesopic
Different mixtures of wavelengths that look identical. More generally, any pair of stimuli that are perceived as identical in spite of physical differences	Metamers
An afterimage whose polarity is the opposite of the original stimulus. Light stimuli produce dark negative afterimages.	Negative afterimage
The point at which an opponent colour mechanism is generating no signal. If red-green and blue-yellow mechanisms are at their neutral points, a stimulus will appear achromatic	Neutral point
The theory that perception of colour is based on the output of three mechanisms, each of them resulting from an opponency between two colours: red-green, blue-yellow and black-white	Opponent colour theory
Referring to cells in the parvocellular layers of the lateral geniculate nucleus of the thalamus. From Greek for "small" referring to the size of the cells	Parvocellular
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
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 colour discriminations based on wavelength	Principle of univariance
An individual who suffers from colour-blindness that is due to the absence of L-cones	Protanope
The percentage of light hitting a surface that is reflected and not typically absorbed into the surface. Typically reflectance is given as a function of wavelength	Reflectance
A colour, such as brown or grey, that is seen only in relation to other colours. For example, a 'grey' patch in complete darkness appears white	Related colour
An individual with no cones of any type. In addition to being truly colour-blond, rod monochromats are badly visually impaired in bright light	Rod monochromat
A cone that is preferentially sensitive to short wavelengths; colloquially known as a 'blue cone.'	S-cone
Referring to light intensities that are bright enough to stimulate the rod receptors but too dim to stimulate the cone receptors	Scotopic
The physical energy in a light as a function of wavelength	Spectral power distribution
The percentage of a particular wavelength that is reflected from a surface	Spectral reflectance function
The sensitivity of a cell or a device to different wavelengths on the electromagnetic spectrum	Spectral sensitivity
A mixture of pigments. If pigment 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 colour	Subtractive colour mixture
Referring to the rare situation (in humans, at least) where the colour of any light is defined by the relationships of four numbers - the outputs of those four receptor types	Tetrachromatic
The theory that the colour of any light is defined in our visual system by the relationships of three numbers 0 the outputs of three receptor tups no known to be three cones. Also called the Young-Helmholtz theory	Trichromacy or trichromatic theory of colour vision
An individual who suffers from colour blindness that is due to the absence of S-cones	Tritanope
Any of four colours that can be described with only a single colour term: Red, yellow, green, blue. Other colours (purple or orange), can also be described as compounds	Unique hue
A colour that can be experienced in isolation	Unrelated colour