The influence of efferent, proprioceptive, and timing factors on the accuracy of eye-hand tracking.

Oculomotor tracking of one's moving hand is considerably more accurate than tracking of an external target undergoing comparable motion. To identify the factors contributing to this enhancement of tracking accuracy, the influence of visual, proprioceptive, and efferent cues on tracking performance was assessed. Related observations were made on the influence both of linear and topological transformations between target and hand position on tracking accuracy. The experimental findings indicate that if a target light is attached to one's hand, a) the target can be tracked with comparable accuracy for active and passive limb movements, and b) when the entire hand rather than just the target light is visible, pursuit velocity is higher and more closely matches target velocity. If a linear transformation is introduced between hand and target positions, nearly identical tracking accuracy is found with voluntary and involuntary limb movements. By contrast, topological transformations degrade target tracking accuracy for passive but not for voluntary limb movements. The implications of this finding are discussed.