Abstract
Convex regions are more likely to appear as objects (figures) than abutting concave regions, but context modulates this likelihood: In 100-ms displays, convex regions are increasingly likely to be seen as figures as the number of alternating convex and concave regions increases from 2 to 8 (57% - 89%; Peterson & Salvagio, 2008). These convexity-context effects occur only when the concave regions are uniform in color. We hypothesized that convexity-context effects arise when the interpretation of a single large surface pre-empts that of multiple same-color concave figures, which then allows convex figures to dominate. We investigated whether it takes time for surface pre-emption to occur by presenting a mask at different inter-stimulus-intervals (ISIs) after the figure-ground display, following a tradition in which masks are used to test the dynamics of visual processing. When the mask immediately followed the 100-ms display (0-ms ISI), simple effects of convexity were observed in that convex regions were seen as figure significantly more often than chance (56%), p . 20. When the onset of the mask was delayed by 100 ms, convexity-context effects were evident, p <. 01, and the pattern was significantly different from that obtained in the 0-ms ISI condition, p .70. Our results indicate that more time is required for convexity-context effects than for simple effects of convexity, perhaps because it takes time for surface interpolation and pre-emption to occur. We interpret these results within a recurrent model of figure-ground perception in which figure assignment emerges from interactions between as well as within levels of the hierarchical visual system.