Abstract
Past research on aging and stereopsis has typically utilized static patterns of binocular disparity. In the present experiment, we explored the ability of younger (less than 30 years of age) and older (greater than 60 years) observers to discriminate 3-D shape from dynamic patterns of binocular disparity. The observers were required to discriminate between curved and noncurved 3-dimensional (3-D) surfaces (sine wave modulated in depth, square wave, or ramp). The spatial frequency of the surfaces was 1/4 cycle per degree. Discrimination accuracies were obtained for 18 distinct experimental conditions formed by the orthogonal combination of 3 surface point lifetimes (13.3 msec, 40 msec, and unlimited), 3 magnitudes of binocular correspondence (100%, 70%, and 40%), and 2 magnitudes of disparity (1.2 and 2.1 minutes arc for the younger observers, and 2.1 and 3.5 minutes arc for the older observers). The results demonstrated large and systematic effects of age — e.g., the discrimination accuracies for the older observers were, on average, 23 percent lower than those for the younger observers in comparable conditions. The reductions in binocular correspondence, however, adversely affected the performance of both age groups equally. The two age groups were differentially affected by the dynamic stereograms. For the younger observers, their discrimination performance was higher for the dynamic stereograms than for the static stereograms; there was no such superiority for the older observers (i.e., the performance of the older observers was identical for both the static and dynamic stereograms). In summary, the results demonstrate that the perception of 3-D shape from binocular disparity does decline with age. However, the results of the experiment also reveal that older observers can perform as well as younger observers if they are given more binocular disparity.