Enhancing Sensitivity to Visual Motion.

This report reviews a one-year investigation of techniques that might enhance an observers sensitivity to moving targets. The five experiments reported here cover a broad range of such techniques. Experiment I measured direction difference thresholds as a function of target velocity for 39 observers. Despite large nearly fourfold individual differences in thresholds, it was clear that ability to tell what direction a target moved in depended strongly on its velocity. In addition, this ability was seriously degraded for an oblique direction compared to performance with upward motion. Experiment II showed that this variation in threshold with target velocity was independent of the distance traveled by that target. This finding contradicts one common theory of motion preception. Experiment III measured difference thresholds for direction at various points in the course of training with a reaction time task. This task required observers to respond rapidly to moving targets presented after exposure to the broadband or filtered directional noise. The reaction times to motion onset decreased with practice but the direction difference thresholds did not show any comparable change. Experiment IV examined the effect of practice on the performance deficit produced by an observers uncertainty about the direction in which a to-be-detected target would travel.