Suppressive effect of multimodal surface representation on ocular smooth pursuit of invisible hand

A human observer can smoothly pursue her/his own voluntarily moved hand with the eyes in total darkness. The effects of a perceived stationary surface during ocular pursuit of the invisible hand were investigated. The task was to track the invisible hand smoothly with the eyes in a Ganzfeld (experiment 1), with a stationary visual surface in the light (experiment 2), or with a solid stationary surface in total darkness (experiment 3). It was found that smooth pursuit of the invisible hand occurred in the Ganzfeld as well as in total darkness, but was replaced by frequent saccades when a stationary surface was perceived through either the visual or the tactile sense. The results obtained with a Ganzfeld suggest that light alone does not prevent smooth pursuit of the invisible hand, and those obtained with a stationary surface suggest that perception of such a surface prevents smooth pursuit of the invisible hand and evokes saccades, regardless of the sense modality.