Effect of disparity on the perception of motion-defined contours.

Abstract

We present three experiments that explored the effect of binocular disparity on the perception of contours defined by motion in a Spatiotemporal Boundary Formation. Depending on the disparity, the stimulus is perceived as an object that moves behind a holed surface (occluded configuration) or as a luminous transparency that moves over a surface that contains dots (occluding configuration). In all of the experiments, we used a Vernier task to assess the strength of contour perception. In the first experiment, we measured acuity as a function of disparity for a range of speeds and dot densities. The results showed that, despite the difference in the percepts, acuity was similar in both situations, replicating the dependence on speed and dot density demonstrated in previous studies. In the second experiment, the results showed that the dynamics of contour integration were identical for both occluded and occluding configurations. In the third experiment, we tested whether the mechanism of contour integration works independently from the interpretation of the scene. In this experiment, we inverted the disparity during stimulus presentation so that the stimulus switched between occluded and occluding configurations. The results showed that the switch of the depth order increased the threshold to the value obtained with a shorter presentation time. This might be produced by a resetting of the integration process driven by the change of depth order. The results are discussed within a conceptual model that places the process of contour integration in the context of the perception of objects in a Spatiotemporal Boundary Formation.

From Flashes to Edges to Objects: Recovery of Local Edge Fragments Initiates Spatiotemporal Boundary Formation

“…These findings offer new insight about the perception of contours and objects from sparse texture element changes. Most previous SBF displays had exclusively used 2D virtual objects (e.g., Shipley and Kellman, 1993a , 1994 , 1997 ; Cicerone et al, 1995 ; Cunningham et al, 1998 ; Erlikhman et al, 2014 ; but see Chambeaud et al, 2014 ). The demonstration that SBF can occur for short edge fragments indicates that such fragments can be recovered without more global shape information and that such fragments are the likely basic units in SBF.…”