An important function of the human visual system is to recover information regarding movement of objects in the environment and movement of the observer through the environment. The recovery of this information by the visual system is performed by two distinct analyses. One analysis is concerned with extracting differential invariant information from the directions of local image velocities. The second analysis is concerned with integrating speed and direction information over large regions of the visual field. Our previous research on motion perception and aging has examined age-related differences in perceiving 2D motion (e.g., motion coherence) and has examined age-related differences in performing perceptual tasks based on differential invariants (e.g., surface detection and identification, relative depth, collision detection). These studies have documented age-related declines in performing complex perceptual tasks dependent on one analysis of the visual system. The proposed research will examine age-related differences in processes responsible for the second analysis---integrating velocity information. The proposed research is designed to examine this issue by conducting studies on basic motion sensitivity, conducting studies on motion information for performing perceptual tasks, and conducting studies on aging and the use of such information during driving. Specifically, experiments will be conducted to (1) assess age related differences in integrating speed information, (2) assess age-related differences in integrating direction information, (3) determine the relationship between age-related differences in integrating velocity and the performance of observer motion tasks on perceived self-motion, the perception of heading, the perception of egospeed, and the detection of collisions, and (4) examine the relationship between the integration of velocity information and the performance of driving tasks. This research will provide an understanding of the visual mechanisms responsible for velocity integration, how age-related changes in these mechanisms determines the successful performance of high level tasks during observer motion, and how age-related differences in perceptual tasks associated with driving are the result of age-related differences in velocity integration. The results of this research will be beneficial in understanding the increased accident risk associated with age.
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