Effects of non-uniform environment damping on haptic perception and performance of aimed movements

A set of experiments was conducted to investigate the relationship of environment damping to performance of a Fitts one-shot tapping task, and especially the relationship of environment damping to the haptic perception of target position. In the experiments, subjects were asked to locate a narrow target region that had a different level of viscous damping than the background regions. The task was performed using a one degree-of-freedom manipulandum. Movement time to target was measured as a function of the damping in the target and background regions. Different visual feedback conditions were also tested. The most striking result of the experiments was that when the targets were not visible to subjects, performance was very closely correlated with the absolute magnitude of the difference in target and environment damping (i.e. target damping minus the background damping). Performance did not vary with the percentage difference between target damping and background damping, nor with the sign of the difference between target and background damping, nor with the level of background damping. When target positions were visible to subjects, performance depended very weakly on the environment damping.