Baseline dependent differences in the perception of changes in visuomotor delay

Abstract

The Weber-Fechner Laws have been evaluated across a wide variety of modalities and tasks, but not yet in the domain of visuomotor mapping. A prominent manipulation of visuomotor mapping is temporal; i.e., delaying visual movement feedback. Yet, while visuomotor delay detection itself has been extensively studied, it is not known whether the perception of changes in delay depends on the present amount of delay. We developed a virtual reality based, continuous hand movement task, during which participants had to detect changes in visuomotor mapping (delay): Participants (N=40) performed continuous, auditory-paced grasping movements, which were measured with a data glove and transmitted to a virtual hand model. The movements of the virtual hand were periodically delayed between 0-700ms; the delay changed repeatedly in a roving oddball fashion in steps of 100-400ms. Participants had to indicate perceived delay changes by key presses, as fast as possible. This design allowed us to investigate detection accuracy and speed related to the magnitude of the delay change, and to the “baseline” delay present during movement. As expected, larger delay changes were detected more accurately than smaller ones. Surprisingly, delay changes were detected more accurately and faster when participants moved under larger delays. These results suggest that visual movement feedback delay affects the detection of changes in visuomotor mapping, but not as predicted by the Weber-Fechner Laws. Rather, smaller visual movement feedback delays likely increased the tolerance for visuomotor changes via an enhanced subjective embodiment of the virtual hand.