Abstract
Most perceptual tasks require the integration of information over space and time. In the present study we examined whether age-related differences exist in the integration of spatio-temporal information from motion. 16 younger (mean age of 21.3) and 16 older (mean age of 74.1) observers were shown random dot patterns specifying one of five shapes whose contours were defined by kinetic occlusion—the accretion and deletion of texture. Three independent variables were examined: presence or absence of kinetic occlusion (object alone or object with background), density (0.61, 1.22, 1.83, or 2.44 dots/deg2), velocity (0.6, 0.8, 1.0, or 1.2 deg/s) and size (4.2 or 6.5 deg height). No age-related effects were found for baseline measures of object motion without kinetic occlusion. However, older observers, as compared to younger observers, had significantly lower sensitivity to stimuli with kinetic occlusion. Older observers, as compared to younger observers, had lower accuracy at lower speeds and density, suggesting that although older observers showed decrements in both spatial and temporal integration, the loss of temporal integration was more pronounced. In a follow up study we examined limitations in temporal integration by varying the lifetime of each dot in the display (2, 3, 4, and 6 frame lifetime). The subjects were 9 younger and 9 older observers from the first study. The results indicate that both older observers, as compared to younger observers, had greater difficulty in identifying shape for the 2 and 3 frame lifetime conditions when the contour was curved (the circle shape).
Supported by NIH AG13419-06