Abstract
Figure-ground perception is determined through competitive interactions. 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-concatenation effects (CCEs) occur only when the concave regions are homogeneous, which led to the proposal that CCEs develop when the interpretation of a single background surface can be fit to concave regions, a fit that becomes increasingly likely with increased numbers of homogeneous concave regions. CCEs take time to develop: For 100-ms masked displays, CCEs are observed with a display- mask ISI of 100 ms, but not with 0- or 50-ms ISIs (Salvagio & Peterson, VSS, 2010). Here, we investigate why it takes time for CCEs to develop. With black-and-white displays used previously, both convex and concave regions were homogeneous, so perhaps a bias to see homogeneous regions as a single surface competed with a bias to see convex regions as figures and the mask cut short the time required to resolve this competition. To remove this potential source of competition we used displays with heterogeneous convex regions and homogeneous concave regions. At both 0- and 50-ms display-mask ISIs, we observed significantly larger CCEs with these displays than with black-and-white displays, ps <.03. Moreover, larger CCEs were observed with a 50- than a 0-ms display-mask ISI, p <.01, indicating that the possibility of perceiving the concave regions as objects also competes with the bias to see homogeneous regions as a single surface, and this competition takes time. Our investigation of the temporal dynamics of CCEs uncovered two previously undocumented competitive interactions in figure-ground perception.
Meeting abstract presented at VSS 2012