Abstract
The bias for young observers to perceive convex regions as figure increases as the number of alternating black and white (BW) convex and concave regions increases from 2 to 8 (Peterson & Salvagio, 2008). Lass et al. (VSS 2012) replicated this convexity context effect (CCE) in younger observers for BW stimuli, but found significantly reduced CCEs in older observers. Based on previous research (Salvagio & Peterson, VSS 2011, 2012), we hypothesized that older observers might have difficulty resolving the competition between figure and ground interpretations for homogeneously coloured convex regions in 8-region BW displays. Salvagio and Peterson reduced competition for convex regions by alternating heterogeneously coloured convex regions with homogenously coloured concave regions. For their younger observers, CCEs emerged earlier in time. We examined whether the convexity bias in older observers is influenced by the colour heterogeneity of convex and concave regions. Older (n = 15) and younger (n = 16) observers viewed four types of 8-region displays blocked by region-type: (1) both-homogeneous (BW), (2) homogeneous-concave/heterogeneous-convex, (3) heterogeneous-concave/homogenous-convex, and (4) both-heterogeneous. On each trial, observers fixated a central border and reported whether a red probe presented to the left or right of center was on or off the region perceived as figure. Probe location was balanced, and the dependent variable was the proportion of trials the convex region was perceived as figure. Convexity biases were larger for displays with homogeneous- versus heterogeneous-concave regions, p <.001; this difference did not differ between age groups. However, the difference between convexity bias measured in the homogeneous-concave and homogeneous-both (BW) conditions was greater in older observers, p <.05. This increase in convexity bias observed in older observers, specifically in displays with reduced competition, indicates that there are age differences in competition resolution ability that affect CCEs, and thus figure assignment more generally.
Meeting abstract presented at VSS 2013