Editing Optical illusion (section)

== Physiological visual illusions ==
Physiological illusions, such as the [[afterimage]]s<ref>{{cite web|url=http://www.worqx.com/color/after_image.htm|title=After Images|work=worqx.com|url-status=live|archive-url=https://web.archive.org/web/20150422033200/http://www.worqx.com/color/after_image.htm|archive-date=2015-04-22}}</ref> following bright lights, or adapting stimuli of excessively longer alternating patterns ([[contingent aftereffect|contingent perceptual aftereffect]]), are presumed to be the effects on the eyes or brain of excessive stimulation or interaction with contextual or competing stimuli of a specific type—brightness, color, position, tile, size, movement, etc. The theory is that a stimulus follows its individual dedicated neural path in the early stages of visual processing and that intense or repetitive activity in that or interaction with active adjoining channels causes a [[physiological]] [[wikt:imbalance|imbalance]] that alters perception.

The Hermann [[grid illusion]] and [[Mach bands]] are two [[illusion]]s that are often explained using a biological approach. [[Lateral inhibition]], where in [[receptive field]]s of the retina receptor signals from light and dark areas compete with one another, has been used to explain why we see bands of increased brightness at the edge of a color difference when viewing Mach bands. Once a receptor is active, it inhibits adjacent receptors. This inhibition creates contrast, highlighting edges. In the Hermann grid illusion, the gray spots that appear at the intersections at peripheral locations are often explained to occur because of [[lateral inhibition]] by the surround in larger receptive fields.<ref>Pinel, J. (2005) Biopsychology (6th ed.). Boston: Allyn & Bacon. {{ISBN|0-205-42651-4}}</ref> However, [[lateral inhibition]] as an explanation of the Hermann [[grid illusion]] [[grid illusion#Theories|has been disproved]].<ref name=Lingelbach_1985>{{cite journal | vauthors= Lingelbach B, Block B, Hatzky B, Reisinger E |year=1985 |title= The Hermann grid illusion -- retinal or cortical? |journal=Perception |volume=14 |issue=1 |pages=A7}}</ref><ref name=Geier_2004>{{cite book|vauthors=Geier J, Bernáth L |year=2004 |chapter= Stopping the Hermann grid illusion by simple sine distortion |title=Perception |pages=33–53 | isbn=978-0631224211 |publisher=Malden Ma: Blackwell}}</ref><ref name="Schiller">{{cite journal | last1=Schiller | first1=Peter H. | last2=Carvey | first2=Christina E. | title=The Hermann grid illusion revisited | journal=Perception | year=2005 | volume=34 | issue=11 | pages=1375–1397 | url=http://www.perceptionweb.com/abstract.cgi?id=p5447 | doi=10.1068/p5447 | pmid=16355743 | s2cid=15740144 | access-date=2011-10-03 | archive-url=https://web.archive.org/web/20111212013609/http://perceptionweb.com/abstract.cgi?id=p5447 | archive-date=2011-12-12 | url-status=dead }}</ref><ref name=Geier_2008>{{cite journal |doi=10.1068/p5622 |vauthors=Geier J, Bernáth L, Hudák M, Séra L |year=2008 |title=Straightness as the main factor of the Hermann grid illusion |journal=Perception |volume=37 |issue=5 |pages=651–665 |pmid=18605141|s2cid=21028439 }}</ref><ref name=Bach_2008>{{cite journal |author=Bach, Michael |year=2008 |title= Die Hermann-Gitter-Täuschung: Lehrbucherklärung widerlegt (The Hermann grid illusion: the classic textbook interpretation is obsolete) | journal=Ophthalmologe | doi=10.1007/s00347-008-1845-5 |pmid=18830602 |volume=106 |issue=10 |pages=913–917|s2cid=1573891 }}</ref>
More recent empirical approaches to optical illusions have had some success in explaining optical phenomena with which theories based on lateral inhibition have struggled.<ref>{{cite journal | last1 = Howe | first1 = Catherine Q. | last2 = Yang | first2 = Zhiyong | last3 = Purves | first3 = Dale | year = 2005 | title = The Poggendorff illusion explained by natural scene geometry | journal = PNAS | volume = 102 | issue = 21| pages = 7707–7712 | doi=10.1073/pnas.0502893102 | pmid=15888555 | pmc=1093311| bibcode = 2005PNAS..102.7707H | doi-access = free }}</ref>