Editing Color (section)

==== Tetrachromacy ====
{{main|Tetrachromacy}}
Outside of humans, which are mostly ''trichromatic'' (having three types of cones), most mammals are dichromatic, possessing only two cones. However, outside of mammals, most vertebrates are ''[[tetrachromatic]]'', having four types of cones. This includes most [[bird]]s,<ref>{{cite journal |last1=Bennett |first1=Andrew T. D. |last2=Cuthill |first2=Innes C. |last3=Partridge |first3=Julian C. |last4=Maier |first4=Erhard J. |year=1996 |title=Ultraviolet vision and mate choice in zebra finches |journal=Nature |volume=380 |issue=6573 |pages=433–435 |bibcode=1996Natur.380..433B |doi=10.1038/380433a0 |s2cid=4347875}}</ref><ref>{{cite journal |last1=Bennett |first1=Andrew T. D. |last2=Théry |first2=Marc |year=2007 |title=Avian Color Vision and Coloration: Multidisciplinary Evolutionary Biology |url=https://hal.archives-ouvertes.fr/hal-02889396/file/Bennett%20%26%20Thery%20Am%20Nat%202007.pdf |journal=The American Naturalist |volume=169 |issue=S1 |pages=S1–S6 |doi=10.1086/510163 |issn=0003-0147 |jstor=510163 |bibcode=2007ANat..169S...1B |s2cid=2484928}}</ref><ref>{{cite book |last1=Cuthill |first1=Innes C. |title=Ultraviolet Vision in Birds |last2=Partridge |first2=Julian C. |last3=Bennett |first3=Andrew T. D. |last4=Church |first4=Stuart C. |last5=Hart |first5=Nathan S. |last6=Hunt |first6=Sarah |date=2000 |publisher=Academic Press |isbn=978-0-12-004529-7 |editor1-last=J. B. Slater |editor1-first=Peter |series=Advances in the Study of Behavior |volume=29 |page=159 |doi=10.1016/S0065-3454(08)60105-9 |editor2-last=Rosenblatt |editor2-first=Jay S. |editor3-last=Snowdon |editor3-first=Charles T. |editor4-last=Roper |editor4-first=Timothy J.}}</ref> [[reptile]]s, [[amphibian]]s, and [[teleost|bony fish]].<ref name="Bowm1">{{cite journal |last1=Bowmaker |first1=James K. |date=September 2008 |title=Evolution of vertebrate visual pigments |journal=Vision Research |volume=48 |issue=20 |pages=2022–2041 |doi=10.1016/j.visres.2008.03.025 |pmid=18590925 |s2cid=52808112 |doi-access=free}}</ref><ref>{{cite journal |last=Vorobyev |first=M. |date=November 1998 |title=Tetrachromacy, oil droplets and bird plumage colours |journal=Journal of Comparative Physiology A |volume=183 |issue=5 |pages=621–33 |doi=10.1007/s003590050286 |pmid=9839454 |s2cid=372159}}</ref> An extra dimension of color vision means these vertebrates can see two distinct colors that a normal human would view as [[metamerism (color)|metamer]]s. Some invertebrates, such as the [[mantis shrimp]], have an even higher number of cones (12) that could lead to a richer color [[gamut]] than even imaginable by humans.

The existence of human tetrachromats is a contentious notion. As many as [[tetrachromacy#Tetrachromacy in carriers of CVD|half of all human females have 4 distinct cone classes]], which could enable tetrachromacy.<ref name="Jameson">{{cite journal|last1=Jameson|first1=K.A.|last2=Highnote|first2=S.M.|last3=Wasserman|first3=L.M.|year=2001|title=Richer color experience in observers with multiple photopigment opsin genes.|doi=10.3758/BF03196159|journal=Psychonomic Bulletin and Review|volume=8|issue=2|pages=244–261 [256]|url=https://link.springer.com/content/pdf/10.3758/BF03196159.pdf |archive-url=https://web.archive.org/web/20131004220637/http://link.springer.com/content/pdf/10.3758/BF03196159.pdf |archive-date=2013-10-04 |url-status=live|pmid=11495112|s2cid=2389566|doi-access=free}}</ref> However, a distinction must be made between ''retinal'' (or ''weak'') ''tetrachromats'', which express four cone classes in the retina, and ''functional'' (or ''strong'') ''tetrachromats'', which are able to make the enhanced color discriminations expected of tetrachromats. In fact, there is only one peer-reviewed report of a functional tetrachromat.<ref>{{cite journal|last1=Jordan|first1=G.|last2=Deeb|first2=S.S.|last3=Bosten|first3=J.M.|last4=Mollon|first4=J.D.|title=The dimensionality of color vision in carriers of anomalous trichromacy|journal=Journal of Vision|date=20 July 2010|volume=10|issue=8|page=12|doi=10.1167/10.8.12|pmid=20884587|doi-access=free}}</ref> It is estimated that while the average person is able to see one&nbsp;million colors, someone with functional tetrachromacy could see a hundred&nbsp;million colors.<ref>{{cite web|last=Kershner|first=Kate|title=Lucky Tetrachromats See World With Up to 100 Million Colors|date=26 July 2016|url=https://science.howstuffworks.com/lucky-tetrachromats-see-world-100-million-colors.htm|access-date=9 February 2022}}</ref>