blindsight a residual visual capacity resulting from lesions in certain areas of the brain (the striate cortex, area 17). Under routine clinical testing, persons suffering such lesions appear to be densely blind in particular regions of the visual field. Researchers have long recognized that, in primates, comparable lesions do not result in similar deficits. It has seemed unlikely that this disparity could be due to differences in brain function, however. And, indeed, when human subjects are tested in the way non-human subjects are tested, the disparity vanishes. Although subjects report that they can detect nothing in the blind field, when required to ‘guess’ at properties of items situated there, they perform remarkably well. They seem to ‘know’ the contents of the blind field while remaining unaware that they know, often expressing astonishment on being told the results of testing in the blind field. See also PERCEPTIO. J.F.H.