On laterality of visual aftereffects: A rejoinder

Abstract

Temporal integration of a dot matrix whose elements are displayed in rapid temporal sequence can be achieved easily, provided that all dots are plotted within a critical temporal interval. The duration of the critical interval is the same whether the stimuli are displayed in the left visual field or in the right visual field (Di Lollo, 1981). These results suggest that duration of visible persistence (restrictively defined as in that article) is probably the same in both cerebral hemispheres. In a commentary on these findings, Wurst and Long (1983) take exception to the inference of hemispheric symmetry in duration of visible persistence because: conclude from one task under one set of stimulus conditions that persistence is not lateralized is presumptuous at. best (p. 595). Here, a brief attempt shall be made at mitigating Wurst and Long's disapprobation. Closer attention will then be paid to more salient issues regarding visible persistence. _ At the basis of Wurst and Long's critique is the belief that, from the results reported in 1981, Di Lollo concluded that the issue of laterality and visual persistence was resolved (p, 595). In fact, no such sweeping conclusion is either stated or implied in that article. Besides, a reading of the complete context shows that what the article set out to resolve was an inconsistency among several sets of experimental data, more so than the issue of lateralization of visible persistence. I do not believe that this sort of issue can be settled in a single study. Were this the sole source of misunderstanding, Wurst and Long's critique would hardly require comment. But there is a more general aspect of the critique that deserves attention, for harks to the definition of the very phenomenon under study. Throughout the article in question (Di Lollo, 1981), a careful distinction was drawn between visible persistence and other nonvisible aftereffects of visual stimulation. To quote, was stressed that it is necessary to distinguish between visible and nonvisible forms of sensory persistence. Such separation is akin to Sperling's (1967) distinction between