Catching What We Can't See: Manual Interception of Occluded Fly-Ball Trajectories

Abstract

Control of interceptive actions may involve fine interplay between feedback-based and predictive mechanisms. These processes rely heavily on target motion information available when the target is visible. However, short-term visual memory signals as well as implicit knowledge about the environment may also contribute to elaborate a predictive representation of the target trajectory, especially when visual feedback is partially unavailable because other objects occlude the visual target. To determine how different processes and information sources are integrated in the control of the interceptive action, we manipulated a computer-generated visual environment representing a baseball game. Twenty-four subjects intercepted fly-ball trajectories by moving a mouse cursor and by indicating the interception with a button press. In two separate sessions, fly-ball trajectories were either fully visible or occluded for 750, 1000 or 1250 ms before ball landing. Natural ball motion was perturbed during the descending trajectory with effects of either weightlessness (0 g) or increased gravity (2 g) at times such that, for occluded trajectories, 500 ms of perturbed motion were visible before ball disappearance. To examine the contribution of previous visual experience with the perturbed trajectories to the interception of invisible targets, the order of visible and occluded sessions was permuted among subjects. Under these experimental conditions, we showed that, with fully visible targets, subjects combined servo-control and predictive strategies. Instead, when intercepting occluded targets, subjects relied mostly on predictive mechanisms based, however, on different type of information depending on previous visual experience. In fact, subjects without prior experience of the perturbed trajectories showed interceptive errors consistent with predictive estimates of the ball trajectory based on a-priori knowledge of gravity. Conversely, the interceptive responses of subjects previously exposed to fully visible trajectories were compatible with the fact that implicit knowledge of the perturbed motion was also taken into account for the extrapolation of occluded trajectories.

Body orientation contributes to modelling the effects of gravity for target interception in humans

“…In well-established notion that fast targets are more difficult to intercept than slow ones (Port et al 1997;Tresilian & Lonergan 2002). Moreover, the responses were timed significantly later for the higher acceleration than the lower acceleration, also consistent with previous results (Bosco et al 2012).…”

“…Moreover, the responses were timed significantly later for the higher acceleration than the lower acceleration, also consistent with previous results (Bosco et al . ).…”

Visual gravitational motion and the vestibular system in humans

“…Occlusion studies show that extrapolation can extend well beyond 1 s durations (Baurès and Hecht, 2011; Bosco et al, 2012). However, the neural model does not solve the motion equations exactly, but provides only an approximate estimate of the trajectory.…”

The common rate control account of prediction motion

“…Likewise, during occlusion, the eyes can track occluded acceleration (Bennett, de Xivry, Barnes, & Lefevre, 2007) occluded curvilinear trajectories (Mrotek & Soechting, 2007) the occluded edge of a rolling wheel (De Freitas, Myers, & Nobre, 2016). Tracking is influenced the predictable effects of gravity and characteristic object motions learned on previous trials (Bosco, Delle Monache, & Lacquaniti, 2012). It seems that the eyes are guided by naturalistic, time-varying representation of occluded moving objects (Bosco et al, 2015).…”