SEGREGATION OF SPATIALLY SUPERIMPOSED OPTIC FLOW COMPONENTS

The transparency phenomenon, which arises when a radial and a rotation al motion pattern are spatially superimposed, suggests that these moti on patterns are processed independently. Indeed, for unrestricted stim ulus durations, observers could identify the rotational pattern as clo ckwise or counterclockwise, and the radial pattern as expansion or con traction, even under uncertainty. However, when the time available to process the compound stimulus was equal to the minimum duration requir ed to identify each of the patterns when presented in isolation, ident ification was impaired. Whereas for spirallike motion patterns the rad ial and rotational components could be identified, radial and rotation al motion patterns were not processed independently when superimposed. Although radial and rotational transformations could not be identifie d simultaneously, a coherent optic flow pattern could be segregated fr om another superimposed optic flow component given definite foreknowle dge.