Perceiving Objects, Scenes and Colour Flashcards
1
Q
Define
Achromatic colours
A
a colour that that lacks hues such as white, grey and black
2
Q
Define
Additive colour mixture
A
the kind of mixing you get if you overlap spotlights in a dark room. The commonly used primary colors of this type are are red, green and blue, and if you overlap all three in effectively equal mixture, you get white light as shown at the center
3
Q
Define
Anomalous trichromatism
A
A form of defective colour vision in which three primary colours are required for colour matching, but the proportion of each primary is not the same as those required by a normal trichromat
4
Q
Define
Apparent movement
A
an optical illusion in which stationary objects viewed in quick succession or in relation to moving objects appear to be in motion
5
Q
Define
Base rate
A
the proportion of individual in the population who show the behaviour of interest in a given psychological testing or assessment situation
6
Q
Define
Baysian inference
A
a method of statistical inference in which Bayes’ theorem is used to update the probability for a hypothesis as more evidence or information becomes available
7
Q
Define
Binding
A
process by which features are combined to create perception of coherent objects
8
Q
Define
Binding problem
A
features of objects are processed separately in different areas of the brain
9
Q
Define
Cerebral achromaropsia
A
a type of color-blindness caused by damage to the cerebral cortex of the brain, rather than abnormalities in the cells of the eye’s retina
10
Q
Define
Chromatic adaptation
A
the human visual system’s ability to adjust to changes in illumination in order to preserve the appearance of object colors
11
Q
Define
Chromatic colours
A
Any color in which one particular wavelength or hue predominates. For example, blue and green
12
Q
Define
Colour blind
A
the decreased ability to see color or differences in color
13
Q
Define
Colour circle
A
an abstract illustrative organization of color hues around a circle, which shows the relationships between primary colors, secondary colors, tertiary colors etc.
14
Q
Define
Colour constancy
A
an example of subjective constancy and a feature of the human color perception system which ensures that the perceived color of objects remains relatively constant under varying illumination conditions
15
Q
Define
Colour matching
A
the process of transferring a particular color across different technologies or platforms
16
Q
Define
Colour solid
A
the three-dimensional representation of a color model, an analog of the two-dimensional color wheel
17
Q
Define
Complementary afterimages
A
a case of perception in which one perceives a subset of the colors available in the external world in a stimulus-shaped local area. They are not illusory opponent hues but localized RGB filtered perception.
18
Q
Define
Contextual modulation
A
stimuli outside of a neuron’s receptive field can affect neural firing
19
Q
Define
Desaturated
A
formed by mixing a color of the spectrum with white
20
Q
Define
Dichromats
A
Organisms with two types of functioning color receptors, called cone cells, in the eyes
21
Q
Define
Double-opponent neurons
A
opponent cells that have a center, which is excited by one color and inhibited by the other. In the surround, the pattern is reversed. Thus, if the center is excited by green and inhibited by red, the surround will be excited by red and inhibited by green
22
Q
Define
Feature integration theory
A
a theory of attention developed in 1980 by Anne Treisman and Garry Gelade that suggests that when perceiving a stimulus, features are “registered early, automatically, and in parallel, while objects are identified separately” and at a later stage in processing
23
Q
Define
Figure
A
an object that is in the foreground of a person’s visual range
24
Q
Define
Figure-ground segregation
A
the fact that the figure is perceived to stand out from the background, being bounded by a closed contour, behind which the background appears to continue
25
# Define
Focused attention stage
the stage of feature integration theory where features are bound into a coherent perception
26
# Define
Gestalt psychology
a school of thought that looks at the human mind and behavior as a whole
27
# Define
Gist of a scene
the structural representation of a scene built during perception
28
# Define
Global image features
describes image as whole whereas local feature represents as image patches
29
# Define
Ground
the most distant points of a person's field of vision when looking at a scene. It serves as a background for the items or "figures" that are closer to the person looking at the scene
30
# Define
Grouping
the process by which visual events are "put together" into units or objects
31
# Define
Illusory contours
visual illusions that evoke the perception of an edge without a luminance or color change across that edge
32
# Define
Inverse projection problem
an image on the retina can be caused by an infinite number of objects
33
# Define
Ishihara plates
a color perception test for red-green color deficiencies, the first in a class of successful color vision tests called pseudo-isochromatic plates ("PIP")
34
# Define
Light-from-above assumption
an assumption that light comes from overhead
35
# Define
Lightness constancy
our ability to perceive the relative reflectance of objects despite changes in illumination
36
# Define
Likelihood principle
the proposition that, given a statistical model, all the evidence in a sample relevant to model parameters is contained in the likelihood function
37
# Define
Metamerism
when two colors that are not actually the same (they reflect different wavelengths of light) appear the same under certain lighting conditions
38
# Define
Metamers
two patches of color that look identical to us in color but are made up of different physical combinations of wavelengths
39
# Define
Monochromatism
complete colour blindness in which all colours appear as shades of one colour
40
# Define
Monochromats
Organisms with the lack of ability to distinguish colors
41
# Define
Nonspectral colours
a colour that is not in the spectrum of visible light. It can be obtained by a mixture of non-continuous wavelengths, like magenta which is a pink obtained by mixing blue and red, the two extremes of the visible spectrum
42
# Define
Oblique effect
people perceive horizontals and vertical more easily than other orientaitons
43
# Define
Opponent neurons
neurons that have an excitatory response to some wavelengths and an inhibitory response to wavelengths in the opponent part of the spectrum
44
# Define
Opponent-process theory of colour vision
ates that the cone photoreceptors are linked together to form three opposing colour pairs: blue/yellow, red/green, and black/white. Activation of one member of the pair inhibits activity in the other
45
# Define
Perceptual organisation
the process of grouping visual elements together so that one can more readily determine the meaning of the visual as a whole
46
# Define
Perceptual segregation
the pulling apart of one portion of a perceptual region from the whole by physical barriers or attention-diverting techniques
47
# Define
Persistence of vision
refers to the optical illusion that occurs when visual perception of an object does not cease for some time after the rays of light proceeding from it have ceased to enter the eye
48
# Define
Physical regularities
regularly occurring physical properties of the environment. For example, there are more vertical and horizontal orientations in the environment than oblique (angled) orientations
49
# Define
Preattentive stage
the stage of feature integration theory where features of objects are separated
50
# Define
Principle of common fate
states that humans perceive visual elements that move in the same speed and/or direction as parts of a single stimulus.
51
# Define
Principle of common region
highly related to proximity. It states that when objects are located within the same closed region, we perceive them as being grouped together
52
# Define
Principle of good continuation
a Gestalt principle of organization holding that there is an innate tendency to perceive a line as continuing its established direction
53
# Define
Principle of good figure
one of several principles referred to as Gestalt principles which asserts that when people are presented with a set of ambiguous. elements (elements that can be interpreted in different ways), they interpret the. elements in the simplest way. Also known as Principle of simplicity or Principle of Pragnanz
54
# Define
Principle of pragnanz
one of several principles referred to as Gestalt principles which asserts that when people are presented with a set of ambiguous. elements (elements that can be interpreted in different ways), they interpret the. elements in the simplest way. Also known as Principle of simplicity or Principle of good figure
55
# Define
Principle of proximity
states that "objects or shapes that are close to one another appear to form groups"
56
# Define
Principle of similarity
states that things which share visual characteristics such as shape, size, color, texture, value or orientation will be seen as belonging together
57
# Define
Principle of simplicity
one of several principles referred to as Gestalt principles which asserts that when people are presented with a set of ambiguous. elements (elements that can be interpreted in different ways), they interpret the. elements in the simplest way. Also known as Principle of Pragnanz or Principle of good figure
58
# Define
Principle of uniform connectedness
the strongest of the Gestalt Principles concerned with relatedness. It refers to the fact that elements that are connected by uniform visual properties are perceived as being more related than elements that are not connected
59
# Define
Principle of univariance
states that one and the same visual receptor cell can be excited by different combinations of wavelength and intensity, so that the brain cannot know the color of a certain point of the retinal image
60
# Define
Reflectance
the measure of the proportion of light or other radiation striking a surface which is reflected off it.
61
# Define
Reflectance curves
the plot of the reflectance as a function of wavelength
62
# Define
Reversible figure-ground
Perceptual changes of which specific elements make up the figure, and which make up the background in indeterminate figures like Rubin's
63
# Define
Saturation
the intensity of color in an image
64
# Define
Segregation
the process of separating one area or object from another
65
# Define
Selective reflection
the reflection emitted by a surface that reflects waves of different lengths with varying intensity
66
# Define
Single-opponent neurons
opponent neurons that have opponent inputs from two or more cone photoreptors
67
# Define
Spectral colours
a color that is evoked in a normal human by a single wavelength of light in the visible spectrum, or by a relatively narrow band of wavelengths, also known as monochromatic light
68
# Define
Structuralism
a method of interpretation and analysis of aspects of human cognition, behaviour, culture, and experience, which focuses on relationships of contrast between elements in a conceptual system
69
# Define
Subtractive colour mixture
Subtractive color mixing is the kind of mixing you get if you illuminate colored filters with white light from behind
70
# Define
Transmission curves
the mathematical function or graph that describes the transmission fraction of an optical or electronic filter as a function of frequency or wavelength
71
# Define
Trichromatic theory of vision
claims that humans perceive color because the eye can receive light of three different wavelengths and combine them into the entire visible spectrum. Also known as the Young-Helmholtz theory
72
# Define
Trichromats
Organisms possessing three independent channels for conveying color information, derived from the three different types of cone cells in the eye
73
# Define
Unconscious inference
perception is indirectly influenced by inferences about current sensory input that make use of the perceiver’s knowledge of the world and prior experience with similar input
74
# Define
Uniform connectedness
elements are defined by areas of the same colour or texture
75
# Define
Unilateral dichromat
trichromatic vision in one eye and dichromatic in other
76
# Define
Value
the light-to-dark dimension of colour
77
# Define
Viewpoint invariance
the phenomenon that enables us to recognize objects regardless of viewing angle
78
# Define
Visual masking stimulus
reduction or elimination of the visibility of one brief (≤ 50 ms) stimulus, called the “target”, by the presentation of a second brief stimulus, called the “mask”
79
# Define
Young-Helmholtz theory
claims that humans perceive color because the eye can receive light of three different wavelengths and combine them into the entire visible spectrum. Also known as the Trichromatic theory of vision
80
# Definition
a colour that that lacks hues such as white, grey and black
Achromatic colours
81
# Definition
the kind of mixing you get if you overlap spotlights in a dark room. The commonly used primary colors of this type are are red, green and blue, and if you overlap all three in effectively equal mixture, you get white light as shown at the center
Additive colour mixture
82
# Definition
A form of defective colour vision in which three primary colours are required for colour matching, but the proportion of each primary is not the same as those required by a normal trichromat
Anomalous trichromatism
83
# Definition
an optical illusion in which stationary objects viewed in quick succession or in relation to moving objects appear to be in motion
Apparent movement
84
# Definition
the proportion of individual in the population who show the behaviour of interest in a given psychological testing or assessment situation
Base rate
85
# Definition
a method of statistical inference in which Bayes' theorem is used to update the probability for a hypothesis as more evidence or information becomes available
Baysian inference
86
# Definition
process by which features are combined to create perception of coherent objects
Binding
87
# Definition
features of objects are processed separately in different areas of the brain
Binding problem
88
# Definition
a type of color-blindness caused by damage to the cerebral cortex of the brain, rather than abnormalities in the cells of the eye's retina
Cerebral achromaropsia
89
# Definition
the human visual system's ability to adjust to changes in illumination in order to preserve the appearance of object colors
Chromatic adaptation
90
# Definition
Any color in which one particular wavelength or hue predominates. For example, blue and green
Chromatic colours
91
# Definition
the decreased ability to see color or differences in color
Colour blind
92
# Definition
an abstract illustrative organization of color hues around a circle, which shows the relationships between primary colors, secondary colors, tertiary colors etc.
Colour circle
93
# Definition
an example of subjective constancy and a feature of the human color perception system which ensures that the perceived color of objects remains relatively constant under varying illumination conditions
Colour constancy
94
# Definition
the process of transferring a particular color across different technologies or platforms
Colour matching
95
# Definition
the three-dimensional representation of a color model, an analog of the two-dimensional color wheel
Colour solid
96
# Definition
a case of perception in which one perceives a subset of the colors available in the external world in a stimulus-shaped local area. They are not illusory opponent hues but localized RGB filtered perception.
Complementary afterimages
97
# Definition
stimuli outside of a neuron's receptive field can affect neural firing
Contextual modulation
98
# Definition
formed by mixing a color of the spectrum with white
Desaturated
99
# Definition
Organisms with two types of functioning color receptors, called cone cells, in the eyes
Dichromats
100
# Definition
opponent cells that have a center, which is excited by one color and inhibited by the other. In the surround, the pattern is reversed. Thus, if the center is excited by green and inhibited by red, the surround will be excited by red and inhibited by green
Double-opponent neurons
101
# Definition
a theory of attention developed in 1980 by Anne Treisman and Garry Gelade that suggests that when perceiving a stimulus, features are "registered early, automatically, and in parallel, while objects are identified separately" and at a later stage in processing
Feature integration theory
102
# Definition
an object that is in the foreground of a person's visual range
Figure
103
# Definition
the fact that the figure is perceived to stand out from the background, being bounded by a closed contour, behind which the background appears to continue
Figure-ground segregation
104
# Definition
the stage of feature integration theory where features are bound into a coherent perception
Focused attention stage
105
# Definition
a school of thought that looks at the human mind and behavior as a whole
Gestalt psychology
106
# Definition
the structural representation of a scene built during perception
Gist of a scene
107
# Definition
describes image as whole whereas local feature represents as image patches
Global image features
108
# Definition
the most distant points of a person's field of vision when looking at a scene. It serves as a background for the items or "figures" that are closer to the person looking at the scene
Ground
109
# Definition
the process by which visual events are "put together" into units or objects
Grouping
110
# Definition
visual illusions that evoke the perception of an edge without a luminance or color change across that edge
Illusory contours
111
# Definition
an image on the retina can be caused by an infinite number of objects
Inverse projection problem
112
# Definition
a color perception test for red-green color deficiencies, the first in a class of successful color vision tests called pseudo-isochromatic plates ("PIP")
Ishihara plates
113
# Definition
an assumption that light comes from overhead
Light-from-above assumption
114
# Definition
our ability to perceive the relative reflectance of objects despite changes in illumination
Lightness constancy
115
# Definition
the proposition that, given a statistical model, all the evidence in a sample relevant to model parameters is contained in the likelihood function
Likelihood principle
116
# Definition
when two colors that are not actually the same (they reflect different wavelengths of light) appear the same under certain lighting conditions
Metamerism
117
# Definition
two patches of color that look identical to us in color but are made up of different physical combinations of wavelengths
Metamers
118
# Definition
complete colour blindness in which all colours appear as shades of one colour
Monochromatism
119
# Definition
Organisms with the lack of ability to distinguish colors
Monochromats
120
# Definition
a colour that is not in the spectrum of visible light. It can be obtained by a mixture of non-continuous wavelengths, like magenta which is a pink obtained by mixing blue and red, the two extremes of the visible spectrum
Nonspectral colours
121
# Definition
people perceive horizontals and vertical more easily than other orientaitons
Oblique effect
122
# Definition
neurons that have an excitatory response to some wavelengths and an inhibitory response to wavelengths in the opponent part of the spectrum
Opponent neurons
123
# Definition
ates that the cone photoreceptors are linked together to form three opposing colour pairs: blue/yellow, red/green, and black/white. Activation of one member of the pair inhibits activity in the other
Opponent-process theory of colour vision
124
# Definition
the process of grouping visual elements together so that one can more readily determine the meaning of the visual as a whole
Perceptual organisation
125
# Definition
the pulling apart of one portion of a perceptual region from the whole by physical barriers or attention-diverting techniques
Perceptual segregation
126
# Definition
refers to the optical illusion that occurs when visual perception of an object does not cease for some time after the rays of light proceeding from it have ceased to enter the eye
Persistence of vision
127
# Definition
regularly occurring physical properties of the environment. For example, there are more vertical and horizontal orientations in the environment than oblique (angled) orientations
Physical regularities
128
# Definition
the stage of feature integration theory where features of objects are separated
Preattentive stage
129
# Definition
states that humans perceive visual elements that move in the same speed and/or direction as parts of a single stimulus.
Principle of common fate
130
# Definition
highly related to proximity. It states that when objects are located within the same closed region, we perceive them as being grouped together
Principle of common region
131
# Definition
a Gestalt principle of organization holding that there is an innate tendency to perceive a line as continuing its established direction
Principle of good continuation
132
# Definition
one of several principles referred to as Gestalt principles which asserts that when people are presented with a set of ambiguous. elements (elements that can be interpreted in different ways), they interpret the. elements in the simplest way. Also known as Principle of simplicity or Principle of Pragnanz
Principle of good figure
133
# Definition
one of several principles referred to as Gestalt principles which asserts that when people are presented with a set of ambiguous. elements (elements that can be interpreted in different ways), they interpret the. elements in the simplest way. Also known as Principle of simplicity or Principle of good figure
Principle of pragnanz
134
# Definition
states that "objects or shapes that are close to one another appear to form groups"
Principle of proximity
135
# Definition
states that things which share visual characteristics such as shape, size, color, texture, value or orientation will be seen as belonging together
Principle of similarity
136
# Definition
one of several principles referred to as Gestalt principles which asserts that when people are presented with a set of ambiguous. elements (elements that can be interpreted in different ways), they interpret the. elements in the simplest way. Also known as Principle of Pragnanz or Principle of good figure
Principle of simplicity
137
# Definition
the strongest of the Gestalt Principles concerned with relatedness. It refers to the fact that elements that are connected by uniform visual properties are perceived as being more related than elements that are not connected
Principle of uniform connectedness
138
# Definition
states that one and the same visual receptor cell can be excited by different combinations of wavelength and intensity, so that the brain cannot know the color of a certain point of the retinal image
Principle of univariance
139
# Definition
the measure of the proportion of light or other radiation striking a surface which is reflected off it.
Reflectance
140
# Definition
the plot of the reflectance as a function of wavelength
Reflectance curves
141
# Definition
Perceptual changes of which specific elements make up the figure, and which make up the background in indeterminate figures like Rubin's
Reversible figure-ground
142
# Definition
the intensity of color in an image
Saturation
143
# Definition
the process of separating one area or object from another
Segregation
144
# Definition
the reflection emitted by a surface that reflects waves of different lengths with varying intensity
Selective reflection
145
# Definition
opponent neurons that have opponent inputs from two or more cone photoreptors
Single-opponent neurons
146
# Definition
a color that is evoked in a normal human by a single wavelength of light in the visible spectrum, or by a relatively narrow band of wavelengths, also known as monochromatic light
Spectral colours
147
# Definition
a method of interpretation and analysis of aspects of human cognition, behaviour, culture, and experience, which focuses on relationships of contrast between elements in a conceptual system
Structuralism
148
# Definition
Subtractive color mixing is the kind of mixing you get if you illuminate colored filters with white light from behind
Subtractive colour mixture
149
# Definition
the mathematical function or graph that describes the transmission fraction of an optical or electronic filter as a function of frequency or wavelength
Transmission curves
150
# Definition
claims that humans perceive color because the eye can receive light of three different wavelengths and combine them into the entire visible spectrum. Also known as the Young-Helmholtz theory
Trichromatic theory of vision
151
# Definition
Organisms possessing three independent channels for conveying color information, derived from the three different types of cone cells in the eye
Trichromats
152
# Definition
perception is indirectly influenced by inferences about current sensory input that make use of the perceiver’s knowledge of the world and prior experience with similar input
Unconscious inference
153
# Definition
elements are defined by areas of the same colour or texture
Uniform connectedness
154
# Definition
trichromatic vision in one eye and dichromatic in other
Unilateral dichromat
155
# Definition
the light-to-dark dimension of colour
Value
156
# Definition
the phenomenon that enables us to recognize objects regardless of viewing angle
Viewpoint invariance
157
# Definition
reduction or elimination of the visibility of one brief (≤ 50 ms) stimulus, called the “target”, by the presentation of a second brief stimulus, called the “mask”
Visual masking stimulus
158
# Definition
claims that humans perceive color because the eye can receive light of three different wavelengths and combine them into the entire visible spectrum. Also known as the Trichromatic theory of vision
Young-Helmholtz theory
159
What is the main challenges of object perception?
* The stimulus on the receptors is ambiguous
* Inverse projection problem: an image on the retina can be caused by an infinite number of objects
* Objects can be hidden or blurred
* Occlusions are common in the environment
* Objects look different from different viewpoints
* Viewpoint invariance: the ability to recognise an object regardless of the viewpoint
160
Who established structuralism?
Wundt
161
What does the Structuralist Approach state?
States that perceptions are created by combining elements called sensations
162
What phenomena can structuralism not explain?
Structuralism could not explain apparent movement or illusory contours
163
List the principles of perceptual organisation
Pragnanz
Similarity
Good continuation
Proximity
Common region
Uniform connectedness
Synchrony
Common fate
164
What are some properties of figure and ground?
* The figure is more "thinglike" and more memorable than ground
* The figure is seen in front of the ground
* The ground is more uniform and extends behind figure
* The contour separating figure from ground belongs to the figure (border ownership)
165
What factors determine which area is a figure?
* Elements located in the lower part of displays
* Units that are symmetrical
* Elements that are small
* Units that are oriented vertically
* Elements that have meaning
166
What are the two types of regularities in the environment?
Semantic regularities
Physical regularities
167
What does physical regularities in the environment include?
Oblique effect
Uniform connectedness
Light-from-above heuristic
168
What are semantic regularities?
Characteristics assocaited with the functions of scenes
169
What is the theory of unconscious inference? What two principles does it include?
* Created by Helmholtz to explain why stimuli can be interpreted in more than one way, but we tend to favour one
* Main principle - perceptions are result of unconscious assumptions about the environment
* Likelihood principle - objects are perceived based on what is most likely to have caused the pattern
170
What theories describe how binding occurs?
Feature integration theory
Illusory conjunctions
171
What are the two stages of feature integration theory?
Preattentive stage: features of objects are separated
Focused attention stage: features are bound into a coherent perception
172
Create a diagram explaining Treisman's (1988) feature integration theory
173
What is Balint's syndrome?
Patients with pariental lobe damage show lack of focused attention results in incorrect combinations of features
174
What are some functions of colour vision?
* Colour signals help us classify and identify objects
* Colour facilitates perceptual organisation of elements into objects
* Colour vision may provide an evolutionary advantage in foraging for food
175
How can we describe colour experience?
* Basic colours are red, yellow, green and blue
* Colour circle shows perceptual relationship among colours
* Colours can be changed by:
* Intensity which changes perceived brightness
* Saturation - adding white to a colour results in less saturated colour
* Wavelength
176
What is the relationship between wavelength and colour perception?
Colour perception is related to the wavelength of light:
* 400-450nm appears violet
* 450-490nm appears blue
* 500-575nm appears green
* 575-590nm appears yellow
* 590-620nm appears orange
* 620-700nm appears red
177
True or False:
Achromatic colours contain no hues
True
178
Who proposed the trichromatic theory of colour vision?
Yound and Helmholtz
179
How many primaries would dichromats use in colour matching tasks?
Two
180
What is the physciological evidence for the trichromatic theory?
* Researchers measured absorption spectra of visual pigments in receptors (1960s)
* They found pigments that responded maximally to:
* Short wavelengths (419nm)
* Medium wavelengths (534nm)
* Long wavelengths (564nm)
* Later researchers found genetic differences for coding proteins for the three pigments (1980s)
181
Colour matching experiments show that colours that are perceptually similar (\_\_\_\_\_\_\_\_\_\_\_\_\_\_) can be caused by different physical wavelengths
Colour matching experiments show that colours that are perceptually similar (**metamers**) can be caused by different physical wavelengths
182
Are three receptor mechanisms necessary for colour perception?
* One receptor type cannot lead to colour vision because:
* Absorption of a photon causes the same effect, no matter what the wavelength is
* Any two wavelengths can cause the same response by changing the intensity
* Two receptor types (dischromats) solve this problem but three types (trichromats) allow for perception of more colours
183
True or False:
Monochromats have rods and cones
False
Monochromats only have rods
184
What are the three types of dichromatism?
Protanopia
Deuteranopia
Tritaniopia
185
What is the behavioural evidence for the opponent-process theory of colour vision?
* Types of colour blindness are red/green and blue/yellow
* Colour afterimages and simultaneous colour contrast show the opposite pairings
186
What is the physiology of opponent-process theory?
Researchers performing single-cells recordings found opponent neurons
* Opponent neurons:
* Are located in the retina and LGN
* Respond in an excitatiry manner to one end of the spectrum and an inhibitory manner to the other
187
Draw a diagram demonstrating how the trichromatic and opponent-process theories work together
188
What are the possible causes of colour constancy?
* Chromatic adaptation - 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
* Adaptation occurs to light sources leading to colour constancy
