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These empirical studies were designed to elucidate the visual mechanisms or channels responsible for the spatiotemporal processing of dynamic imagery. The studies are conveniently placed into four different categories according to the type of display employed. A sustained-transient channels model of visual function was used as the framework for the conduct and interpretation of the experiments. (1) In the first series of studies it was shown that the pattern of masking effects produced by a background of particular spatial frequency content upon a set of test targets cannot be predicted without knowing the temporal characteristics of both the background and target. (2) Studies of the effects of sine-wave adaptation on perceptual organization. Selective adaptation to sine-wave gratings was found to bias the perceptual organization of a bistable spatiotemporal display. (3) Studies with alternating, Julesz-type random-element patterns. In experiments in which the perception of a global subjective figure depended upon local correlations of individual elements in successive time frames, it was found that the clarity of the subjective figure decreased gradually as the orientation difference between elements in the successive frames increased. (4) Studies of dynamic texture processing. The perception of a subjective figure based upon texture cues in a dynamic display was found to depend upon a process which consisted of at least two adaptable components: one component involving a representation or coding of the spatial details of the individual texture elements themselves, and another component involving a representation or coding of the figure as a whole.

This report discusses three main research topics, each of which is interpreted in terms of a spatial frequency analysis model of the human visual system. Parameters which affect the perception of clusters of line elements in dynamic, computer-generated displays are investigated. Transitions between perception of the moving cluster as a group and perception of the motion of the individual elements of the cluster are studied as a function of display frame rate, subject dark adaptation, image contrast, spatial orientation and various positional perturbations of elements in the cluster. The effect of spatial frequency components on eye movement in real-life scenes was studied by correlating eye movement patterns obtained from photographic scenes which were spatially high-pass filtered, low-pass filtered or unfiltered. Results indicate that areas of scenes containing strong low spatial frequency components attract attention more than areas containing strong high spatial frequency components. Velocity coding in the human visual system was studied by means of moving sinusoidal gratings. Results with complex moving gratings indicate that velocity perception depends partially on the temporal variation of intensity at each point on the retina due to the moving pattern. A complex pattern containing a fundamental spatial frequency and higher harmonic components appears to be moving faster than a stimulus consisting of only the fundamental component and moving at the same velocity as the complex pattern.