Beginning with Kraepelin, efforts have been made to find significant differences between the perceptions of psychotic and those of normal subjects, in the hope of using such differences as objective indexes of mental deterioration. But the results have been disappointing. For this reason, among others, subsequent efforts at objectivity and quantification have been concerned with performance and intelligence tests, as typified by the work of Babcock and Wechsler.1 It might be said, somewhat metaphorically, that the present tendencies have been away from Kraepelin's molecular approach, and toward a molar approach. The subject report suggests the feasibility, at least in this one case, of a return to a molecular index—in this instance, an objective visual measure correlated with memory impairment. Such an index could, when fully standardized, have molar implications perhaps for mental deterioration in general.
In 1850 Plateau described the negative after-effects of viewing a slowly rotating disk carrying