Abstract
The occlusion of objects in visual scenes provides valuable information about the environment and kinetic occlusion, the change in occlusion information over time, is particularly important for the formation of edge boundaries of objects as we navigate real-world scenes. Research has shown that increased age impacts our sensitivity to spatial properties of edge boundaries, reducing the ability to integrate discrete elements into cohesive contours (Roudaia, Bennett, & Sekuler, 2011). Other work has shown reductions in older adults’ ability to discriminate 2D shapes based on kinetic occlusion information (Andersen & Ni, 2008). In the current study we compared college aged adults to older adults (M age= 77.4) on an edge discrimination task, asking them to distinguish a curved from a straight edge. The displays consisted of two sequentially presented stimuli, one with a curved left boundary and one with a straight boundary. The stimuli appeared as stationary opaque objects in the center of the screen with a continuous background texture translating horizontally. Curvature sensitivity thresholds were derived using a QUEST adaptive staircase procedure in a four (density of background texture) by three (speed of texture translation) design. Results indicated a main effect of age with older adults demonstrating significantly lower sensitivity to curvature than the younger adults. The main effect of both density and speed of the moving background texture was significant for both age groups, with increases in either resulting in increased curvature sensitivity. There was no significant interaction between age and either density or speed. However, when comparing conditions with matched rates of accretion and distinct density and speed values, it was found that younger adults appeared to benefit at the highest levels of density more so than did older adults. This result indicates a possible deficit in older adults’ ability to spatially integrate occlusion information to perceive edges.