Phenomenal Simultaneity with Irregular Timing of Components of the Visual Stimulus

Much information about the operation of the visual system has been garnered from data of experiments employing successive, cyclic stimuli. Spatial (Fry & Bartley, 1936; Granit, 1930; Foley, 1956), temporal (Granit & Hammond, 1931; Murphree, 1954; Battersby & Jaffe, 1953), spatio-temporal (Granit 8: Davis, 1931; Hylkema, 1942), interaction and induction (Motokawa, 1950) effects have been demonstrated. Evidence for chemical (Hecht, 1935; Jahn, 1946) and neural (Crozier & Wolf, 1943; Bartley, 1937) factors, as well as central (Walter & Walter, 1949; Walker, Woolf, Hdstead, & Case, 1943) involvement in these phenomena has been given. Dynamic models of visual system operation (Stroud, 1956; De Lange, 1952) have been constructed, based in part on data from such experiments. These researches might be characterized as psycho-physiological. In the context of the Gestalt school, pioneering contributions to the understanding of temporal factors in vision were made by Wertheirner ( 1912 ) by his specification of conuolling variables for simultaneity and apparent movement. Korte (1915) followed soon after and set forth his laws, concerning, among other variables, the time between visual stimuli necessary for optimal apparent movement. These laws have since been amended and modified by subsequent experimentation, notably that of Neuhaus (1930). With rare exception, however, flash-type stimuli used in these experiments came in regular succession, repeated at fixed, constant intervals, or else consisted of only two or three sequential elements. This being so, ic seemed vital to investigate the effects of trregalar, arhythmic (as well as regular), temporal cyclic patterns of visual flash presentation, anticipating that results of the interplay of such temporal factors might yield some useful new insights about the foregoing aspects of visual function. In accordance with the aim stated, a configuration of four pinhole-size dots of light, one at each corner of a diamond, was selected as the spatial pattern over which the stimuli of the experiment were presented. The four dots, flashed in sequence, constituted one cycle in a continuous train of cycles pre-

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