Visual factors that determine sensory uncertainty in rapid interceptive hand movements.

Tracking and intercepting a moving object requires predicting its trajectory, an ability that depends on the reliability of the available motion information. We investigated two common sources that limit the reliability (certainty) of visual motion information during laboratory object interception: how long an object is shown and how long it is occluded. A simulated flyball was shown briefly on a screen and then occluded before it entered a hit zone. Observers tracked the trajectory of the ball with their eyes and intercepted it in the hit zone with a rapid pointing movement. In a two-part experiment, we either varied the presentation of the ball or occlusion duration. Short presentation duration produced a strong center bias in hand movements, but long occlusion duration yielded only a weak center bias. Whereas the center bias merely improved with long presentation durations, it was fully resolved when occlusion duration was short. These findings indicate that sensorimotor decisions under uncertainty might have to rely more on priors when an object is presented briefly versus when it is occluded for longer periods. Eye and hand movement accuracy were correlated across levels of uncertainty, confirming that predictive processes guiding these effectors share a common readout of motion information.