Contour Interaction in Visual Space: Depth Separation and Visual Masking.

摘要

Virtually all research on inhibitory interactions among adjacent visual stimuli operative in such phenomena as simultaneous contrast and visual masking has employed situations in which the interacting stimulus elements occupy the same depth plane (i.e., have the same z-axis values) in deference to the implicit assumption that the processing of depth information occurs only after the visual processing of contour information is completed. But there are theoretical reasons and data suggesting that the interactions among contours depends critically upon their relative positions in depth--interactions may not occur if the stimulus elements occupy different depth positions. The extent to which metacontrast masking depends upon depth position was investigated in nine experiments that used stereoscopic contours formed from random-element stereograms as test and mask stimuli. The stereogram generation system permits large variations in depth to be made without introducing confounding changes in proximal stimulation. The main results are: (1) Separation of test and mask stimuli in depth substantially reduces masking; and (2) When more than one stimulus is in visual space; the stimulus that either appears first or appears closer to the observer receives preferential processing by the visual system. (Author)