Editing Contrast effect (section)

=== Simultaneous contrast ===
The oldest reference to simultaneous contrast in the scientific literature is by the hand of the 11th century physicist [[Ibn al-Haytham]] who describes spots of paint on a white background appearing almost black and conversely paler than their true colour on black:<ref name=aH>أبو علي، الحسن بن الحسن بن الهيثم: 1011–1021, [https://ar.wikisource.org/wiki/%D9%83%D8%AA%D8%A7%D8%A8_%D8%A7%D9%84%D9%85%D9%86%D8%A7%D8%B8%D8%B1/%D8%A7%D9%84%D9%85%D9%82%D8%A7%D9%84%D8%A9_%D8%A7%D9%84%D8%A3%D9%88%D9%84%D9%89/%D8%AA%D8%A7%D8%A8%D8%B9_%D8%A7%D9%84%D9%81%D8%B5%D9%84_%D8%A7%D9%84%D8%B3%D8%A7%D8%AF%D8%B3 كتاب المناظر], 1 § 6 ¶ 113–114</ref>
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He also describes that a leaf green paint may appear clearer and younger on dark blue and darker and older on yellow:<ref name=aH/>
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[[Johann Wolfgang von Goethe]] writes in 1810 that a grey image on a black background appears much brighter than the same on white.<ref>Johann Wolfgang von Goethe: ''Zur Farbenlehre'' III § 38: ‘Ein graues Bild auf ſchwarzem Grunde erſcheint viel heller, als daſſelbe Bild auf weißem. Stellt man beyde Faͤlle neben einander, ſo kann man ſich kaum uͤberzeugen, daß beyde Bilder aus Einem Topf gefaͤrbt seyen.’</ref> And [[Johannes Peter Müller]] 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.<ref>Johannes Peter Müller: ''Handbuch der Physiologie des Menschen'' V <sup>§</sup> I § III ¶ 3B2: ‘So z. B. erscheint der graue Papierschnitzel leicht röthlich auf grünem Felde, dagegen grünlich auf rothem Felde, mit orangefarbener Nebentinte auf hellblauem Felde, und mit bläulicher Tinte auf orangenem Felde, gelblich auf hellvioletem Felde, violet auf hellgelbem Felde.’</ref>
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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,<ref>Joseph C. Stevens: ''Brightness inhibition re size of surround''</ref> as does the separation between colour and surround,<ref>Robert E. Cole & A. Leonard Diamond: ''Amount of surround and test-inducing separation in simultaneous brightness contrast''</ref> similarity of [[chromaticity]],<ref>Tadasu Oyama, Muneo Mitsuboshi & Takashi Kamoshita: ''Wavelength-specific brightness contrast as a function of surround luminance''</ref> luminance difference<ref>María José Luque, Pascual Capilla, Adelina Felipe & José María Artigas: ''Brightness induction in a chromatic center – achromatic surround configuration''</ref> and the structure of the surround.<ref>Michael White: ''The effect of the nature of the surround on the perceived lightness of grey bars within square-wave test gratings''</ref><ref>Edward Howard Adelson: ''Perceptual organization and the judgment of brightness''</ref><ref>Iris K. Zemach, & Michael E. Rudd: ''Effects of surround articulation on lightness depend on the spatial arrangement of the articulated region''</ref>

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.<ref>{{Cite journal|doi = 10.1068/p260673|title = Simultaneous Contrast: The Legacies of Hering and Helmholtz|year = 1997|last1 = Kingdom|first1 = Fred|journal = Perception|volume = 26|issue = 6|pages = 673–677|pmid = 9474338|s2cid = 411796|doi-access = free}}</ref> Both appear to have some effect. A possible source of the effect are neurons in the [[Visual cortex#V4 | 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.