Abstract
Previous work on cue combination of optic flow and disparity cues for surface shape perception has suggested that these cues are processed independently to generate separate shape estimates which are combined in a statistically optimal fashion. In this study, we investigate whether these cues are independently processed for velocity perception of motion-in-depth. We psychophysically investigated visual cue integration of optic flow and disparity by testing 3 subjects on a 2AFC-relative velocity-in-depth judgment task. The velocity-in-depth specified by each cue was independently manipulated for a flat mesh object randomly generated each trial by a Delaunay triangulation. We examined the effects of adding each of two types of noise, disparity noise and optic flow noise, to the stimuli to determine the effect on discrimination thresholds for each cue in isolation and in combination. Independence predicts that cue thresholds will only be affected by noise to that cue. The results did not support independent processing of the cues. In particular, optic flow noise resulted in a concomitant increase in both optic flow and disparity thresholds. Disparity noise, on the other hand, only affected disparity thresholds, without affecting optic flow thresholds. Cue combination thresholds in every condition were significantly greater than predictions of an independence (weak fusion) model of cue combination. A strong fusion (dependence) model of disparity and optic flow cue combination for relative velocity-in-depth discriminations is suggested by our findings.
This research was partially supported by NIH EY015261-01.