Control of attention in the processing of temporal and spatial information in complex visual patterns.

Eighteen stimuli were created by orthogonally varying the area (A), perimeter (P), and exposure duration of checkerboard patterns. Subjects judged either the area and duration of the presented shapes (area-time group) or the perimeter and duration (perimeter-time group) of the same figures. Perceived duration, area, and perimeter varied with changes in the uninstructed an the instructed stimulus dimensions. The discussion focuses on the ability of subjects to control the allocation of attention to instructed stimulus dimensions, as well as on the evidence in the data in favor of detailed sequential or fast holistic processing. It is suggested that the concept of stimulus complexity, defined as P2/A, is useful in describing the temporal and spatial illusions obtained in this study.