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A contrast effect is the enhancement or diminishment, relative to normal, of
perception Perception () is the organization, identification, and interpretation of sensory information in order to represent and understand the presented information or environment. All perception involves signals that go through the nervous syste ...
,
cognition Cognition refers to "the mental action or process of acquiring knowledge and understanding through thought, experience, and the senses". It encompasses all aspects of intellectual functions and processes such as: perception, attention, though ...
or related performance as a result of successive (immediately previous) or simultaneous exposure to a
stimulus A stimulus is something that causes a physiological response. It may refer to: *Stimulation **Stimulus (physiology), something external that influences an activity **Stimulus (psychology), a concept in behaviorism and perception *Stimulus (economi ...
of lesser or greater value in the same dimension. (Here, normal perception, cognition or performance is that which would be obtained in the absence of the comparison stimulus—i.e., one based on all previous experience.) Perception example: A neutral gray target will appear lighter or darker than it does in isolation when immediately preceded by, or simultaneously compared to, respectively, a dark gray or light gray target. Cognition example: A person will appear more or less attractive than that person does in isolation when immediately preceded by, or simultaneously compared to, respectively, a less or more attractive person. Performance example: A laboratory rat will work faster, or slower, during a stimulus predicting a given amount of reward when that stimulus and reward are immediately preceded by, or alternated with, respectively, different stimuli associated with either a lesser or greater amount of reward.


Types


Simultaneous contrast

The oldest reference to simultaneous contrast in the scientific literature is by the hand of the 11th century physicist
Ibn al-Haytham Ḥasan Ibn al-Haytham, Latinized as Alhazen (; full name ; ), was a medieval mathematician, astronomer, and physicist of the Islamic Golden Age from present-day Iraq.For the description of his main fields, see e.g. ("He is one of the pr ...
who describes spots of paint on a white background appearing almost black and conversely paler than their true colour on black:أبو علي، الحسن بن الحسن بن الهيثم: 1011–1021
كتاب المناظر
1 § 6 ¶ 113–114
He also describes that a leaf green paint may appear clearer and younger on dark blue and darker and older on yellow:
Johann Wolfgang von Goethe Johann Wolfgang von Goethe (28 August 1749 – 22 March 1832) was a German poet, playwright, novelist, scientist, statesman, theatre director, and critic. His works include plays, poetry, literature, and aesthetic criticism, as well as t ...
writes in 1810 that a grey image on a black background appears much brighter than the same on white. And
Johannes Peter Müller Johannes Peter Müller (14 July 1801 – 28 April 1858) was a German physiologist, comparative anatomist, ichthyologist, and herpetologist, known not only for his discoveries but also for his ability to synthesize knowledge. The paramesonephri ...
notes the same in 1838 and also that a strip of grey on a brightly coloured field appears to be tinted ever so slightly in the contrasting colour.
The subject of the impact of the surrounding field on colour perception has been a subject of ongoing research since. It has been found that the size of the surrounding field has an impact, as does the separation between colour and surround, similarity of chromaticity, luminance difference and the structure of the surround. There has been some debate over the degree to which simultaneous contrast is a physiological process caused by the connections of neurons in the visual cortex, or whether it is a psychological effect. Both appear to have some effect. A possible source of the effect are neurons in the V4 area that have inhibitory connections to neighboring cells. The most likely evolutionary rationale for this effect is that it enhances edges in the visual field, thus facilitating the recognition of shapes and objects.


Successive contrast

Successive contrast occurs when the perception of currently viewed stimuli is modulated by previously viewed stimuli. In the example below you can use the scrollbar to quickly swap the red and green disks for two orange disks. Staring at the dot in the centre of one of the top two coloured disks and then looking at the dot in the centre of the corresponding lower disk makes the two lower disks briefly appear to have different colours, though in reality their colour is identical.
 
 


Metacontrast and paracontrast

Metacontrast and paracontrast involve both time and space. When one half of a circle is lit for 10
millisecond A millisecond (from '' milli-'' and second; symbol: ms) is a unit of time in the International System of Units (SI) equal to one thousandth (0.001 or 10−3 or 1/1000) of a second and to 1000 microseconds. A unit of 10 milliseconds may be calle ...
s (ms), it is at its maximal intensity. If the other half is displayed at the same time (but 20–50 ms later), there is a mutual inhibition: the left side is darkened by the right half (''metacontrast''), and the center may be completely obliterated. At the same time, there is a slight darkening of the right side due to the first stimulus (''paracontrast'')."Eye, human". Encyclopædia Britannica. 2008.
Encyclopædia Britannica 2006 Ultimate Reference Suite DVD An encyclopedia (American English) or encyclopædia (British English) is a reference work or compendium providing summaries of knowledge either general or special to a particular field or discipline. Encyclopedias are divided into articles ...
.


Domains

The contrast effect was noted by the 17th century philosopher
John Locke John Locke (; 29 August 1632 – 28 October 1704) was an English philosopher and physician, widely regarded as one of the most influential of Enlightenment thinkers and commonly known as the "father of liberalism". Considered one of ...
, who observed that lukewarm water can feel hot or cold depending on whether the hand touching it was previously in hot or cold water. In the early 20th century,
Wilhelm Wundt Wilhelm Maximilian Wundt (; ; 16 August 1832 – 31 August 1920) was a German physiologist, philosopher, and professor, known today as one of the fathers of modern psychology. Wundt, who distinguished psychology as a science from philosophy and ...
identified contrast as a fundamental principle of perception, and since then the effect has been confirmed in many different areas. Contrast effects can shape not only visual qualities like color and brightness, but other kinds of perception, including the perception of weight. Whether a piece of music is perceived as good or bad can depend on whether the music heard before it was unpleasant or pleasant. For the effect to work, the objects being compared need to be similar to each other: a television reporter can seem to shrink when interviewing a tall basketball player, but not when standing next to a tall building. Furthermore, the contrast effect has been argued to apply to foreign policies of states. For example, African countries have increasingly looked to China and India as opposed to the US, the EU and the World Bank because these Asian states have highlighted their lack of "interference" and "conditionality" in exchange for foreign aid and FDI.


See also

*
Assimilation and contrast effects The assimilation effect, assimilation bias or biased assimilation is a bias in evaluative judgments towards the position of a context stimulus, while contrast effects describe a negative correlation between a judgment and contextual information. ...
*
Checker shadow illusion The checker shadow illusion is an optical illusion published by Edward H. Adelson, professor of vision science at MIT in 1995. Description The image depicts a checkerboard with light and dark squares, partly shadowed by another object. The op ...
* Chubb illusion * Less-is-better effect and distinction bias *
Negative (Positive) contrast effect Behavioral contrast refers to a change in the strength of one response that occurs when the rate of reward of a second response, or of the first response under different conditions, is changed. For example, suppose that a pigeon in an operant chamb ...
*
List of cognitive biases Cognitive biases are systematic patterns of deviation from norm and/or rationality in judgment. They are often studied in psychology, sociology and behavioral economics. Although the reality of most of these biases is confirmed by reproducible re ...


References

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External links


WebExhibits - Simultaneous Contrast


* ttp://colorisrelative.com/bwbox.html Interactive Classic Black and White example of simultaneous contrast
Pioneer article which explicates the relevance of the contrast effect to foreign policies of countries
Perception Cognition Cognitive biases Vision Psychophysics