Abstract
A single experiment required 28 younger and older adults to discriminate global shape as defined by differences in texture. The stimulus patterns were 3-point micropattern textures (cf, Caelli & Julesz, 1978). On any given trial, a texture-defined shape (either a vertically- or horizontally-oriented rectangle) was presented; the observers' task was to discriminate between the two rectangles. The task difficulty was manipulated by varying the deviation from colinearity of each of the individual 3-point texture elements between figure and background (the larger the difference in deviation between figure and ground, the higher the discrimination performance). A substantial effect of age was found: in order to perceive the target rectangle and discriminate its shape with a d’ value of 1.5, the older observers needed differences from colinearity that were 54.4 percent larger than those required for younger adults. The results indicate that while older adults can visually perceive global shape defined only by differences in texture, their abilities are nevertheless significantly compromised.