David Bourget (Western Ontario)
David Chalmers (ANU, NYU)
Rafael De Clercq
Jack Alan Reynolds
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Consciousness and Cognition 7 (3):410-423 (1998)
Cortical color blindness, or cerebral achromatopsia, has been likened by some authors to ''blindsight'' for color or an instance of ''covert'' processing of color. Recently, it has been shown that, although such patients are unable to identify or discriminate hue differences, they nevertheless show a striking ability to process wavelength differences, which can result in preserved sensitivity to chromatic contrast and motion in equiluminant displays. Moreover, visually evoked cortical potentials can still be elicited in response to chromatic stimuli. We suggest that these demonstrations reveal intact residual processes rather than the operation of covert processes, where proficient performance is accompanied by a denial of phenomenal awareness. We sought evidence for such covert processes by conducting appropriate tests on achromatopsic subject M.S. An ''indirect'' test entailing measurement of reaction times for letter identification failed to reveal covert color processes. In contrast, in a forced choice oddity task for color, M.S. was unable to verbally indicate the position of the different color, but was surprisingly adept at making an appropriate eye movement to its location. This ''direct'' test thus revealed the possible covert use of chromatic differences
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Alan Cowey & Charles A. Heywood (1997). Cerebral Achromatopsia: Colour Blindness Despite Wavelength Processing. Trends in Cognitive Sciences 1 (4):133-139.
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Glyn W. Humphreys, Tom Troscianko, M. J. Riddoch & M. Boucart (1992). Covert Processing in Different Visual Recognition Systems. In A. David Milner & M. D. Rugg (eds.), The Neuropsychology of Consciousness. Academic Press
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Citations of this work BETA
Claudia Carrara Augustenborg (2010). The Endogenous Feedback Network: A New Approach to the Comprehensive Study of Consciousness. Consciousness and Cognition 19 (2):547-579.
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