Editing Blindsight (section)

== Type classification ==
The majority of studies on blindsight are conducted on patients who are [[Hemianopsia|hemianopic]], i.e. blind in one-half of their [[visual field]]. Following the destruction of the left or right striate cortex, patients are asked to detect, localize, and discriminate amongst visual stimuli that are presented to their blind side, often in a forced-response or guessing situation, even though they may not consciously recognize the visual stimulus. Research shows that such blind patients may achieve a higher accuracy than would be expected from chance alone.{{cn|date=January 2024}}

''Type 1 blindsight'' is the term given to this ability to guess—at levels significantly above chance—aspects of a visual stimulus (such as location or type of movement) without any conscious awareness of any stimuli. ''Type 2 blindsight'' occurs when patients claim to have a feeling that there has been a change within their blind area—e.g. movement—but that it was not a visual [[percept]].<ref>{{cite book|vauthors = Weiskrantz L|year=1997|title=Consciousness Lost and Found: A Neuropsychological Exploration|publisher=Oxford University Press|isbn=978-0-19-852301-7|author-link=Lawrence Weiskrantz|url-access=registration|url=https://archive.org/details/consciousnesslos00weis}}</ref> The re-classification of blindsight into Type 1 and Type 2 was made after it was shown that the most celebrated blindsight patient, "GY", was usually conscious of stimuli presented to his blind field if the stimuli had certain specific characteristics, namely being of high contrast and moving fast (at speeds in excess of 20 degrees per second).<ref>{{cite journal|vauthors = Barbur JL, Watson JD, Frackowiak RS, Zeki S|title = Conscious visual perception without V1|journal = Brain|volume = 116 ( Pt 6)|issue = 6|pages = 1293–302|date = December 1993|pmid = 8293272|doi = 10.1093/brain/116.6.1293}}</ref><ref>{{Cite journal|date=2001-12-01|title=Low-Level Phenomenal Vision Despite Unilateral Destruction of Primary Visual Cortex|url=https://www.sciencedirect.com/science/article/abs/pii/S1053810001905264|journal=Consciousness and Cognition|language=en|volume=10|issue=4|pages=574–587|doi=10.1006/ccog.2001.0526|issn=1053-8100|last1=Stoerig|first1=Petra|last2=Barth|first2=Erhardt|pmid=11790045|s2cid=22895605|access-date=2021-04-24|archive-date=2021-04-24|archive-url=https://web.archive.org/web/20210424103119/https://www.sciencedirect.com/science/article/abs/pii/S1053810001905264|url-status=live}}</ref> 

In the aftermath of the [[World War I|First World War]], a neurologist, George Riddoch, had described patients who had been blinded by gunshot wounds to [[Visual cortex|V1]], who could not see stationary objects but who were, as he reported, "conscious" of seeing moving objects in their blind field.<ref>{{Cite journal|vauthors = Riddoch G|date=1917-05-01|title=Dissociation of Visual Perceptions Due to Occipital Injuries, With Especial Reference to Appreciation of movement|journal=Brain|volume=40|issue=1|pages=15–57|doi=10.1093/brain/40.1.15|issn=0006-8950}}</ref> It is for this reason that the phenomenon has more recently also been called the ''[[Riddoch syndrome]]''.<ref name=":2">{{cite journal|vauthors = Zeki S, Ffytche DH|title = The Riddoch syndrome: insights into the neurobiology of conscious vision|journal = Brain|volume = 121 ( Pt 1)|issue = 1|pages = 25–45|date = January 1998|pmid = 9549486|doi = 10.1093/brain/121.1.25|doi-access = free}}</ref>

Since then it has become apparent that such subjects can also become aware of visual stimuli belonging to other visual domains, such as color and [[luminance]], when presented to their blind fields.<ref name=":3">{{cite journal|vauthors = Morland AB, Jones SR, Finlay AL, Deyzac E, Lê S, Kemp S|title = Visual perception of motion, luminance and colour in a human hemianope|journal = Brain|volume = 122 ( Pt 6)|issue = 6|pages = 1183–98|date = June 1999|pmid = 10356069|doi = 10.1093/brain/122.6.1183|doi-access = free}}</ref> The ability of such hemianopic subjects to become consciously aware of stimuli presented to their blind field is also commonly referred to as "residual" or "degraded" vision.<ref name=":4" /><ref name=":5" />

As originally defined, ''blindsight'' challenged the common belief that perceptions must enter consciousness to affect our behavior, by showing that our behavior can be guided by sensory information of which we have no conscious awareness.<ref name="Carlson 2013 4">{{cite book|title=Physiology of Behavior|vauthors = Carlson N|publisher=Pearson Education, Inc.|year=2013|isbn=978-0-205-23981-8|edition=11th|location=University of Massachusetts, Amherst|page=4}}</ref> Since the demonstration that blind patients can experience some visual stimuli consciously, and the consequent redefinition of blindsight into Type 1 and Type 2, a more nuanced view of the phenomenon has developed.<ref name=":5" /><ref name=":2" /><ref name=":4" /> Blindsight may be thought of as a converse of the form of [[anosognosia]] known as [[Anton syndrome]], in which there is full cortical blindness along with the [[confabulation]] of visual experience.