University Behavioral Health Care
Schizophrenia has been extensively studied for over a century but there are not yet any objective tests that reliably tell us about the presence, stage, or state of the illness. Here, I make the case that brief, inexpensive, and noninvasive behavioral assessments of visual functioning yield surprising insights. Three processes are specifically considered: contour integration, in which a collinear group of edges pops out of a cluttered array; collinear facilitation, in which a low contrast oriented element becomes easier to see when flanked by collinear elements; and visual shape completion, in which quartets of sectored circles (pac-men) become easier to discriminate when forming a single globally completed shape. I provide psychophysical evidence that each of the foregoing processes is impaired in schizophrenia. The deficits are large in magnitude, reliant upon specific visual cortical structures, and unexplained by group differences in medication, motivation, or attention. The deficits at times are specific to schizophrenia, arise by the first psychotic episode, and worsen with prolonged illness duration or elevated conceptual disorganization. Taken together, behaviorally established visual deficits may furnish a sort of biomarker, objectively flagging the presence, stage, or state of schizophrenia.