Context effects on smooth pursuit and manual interception of a disappearing target

In our natural environment, we interact with moving objects that are surrounded by richly textured, dynamic visual contexts. Yet, most laboratory studies on vision and movement show visual objects in front of uniform grey backgrounds. Context effects on eye movements have been widely studied, but it is less well known how visual contexts affect hand movements. Here we ask whether eye and hand movements integrate motion signals from target and context similarly or differently, and whether context effects on eye and hand change over time. We developed a track-intercept task requiring participants to track the initial launch of a moving object ("ball") with smooth pursuit eye movements. The ball disappeared after a brief presentation, and participants had to intercept it in a designated "hit zone". In two experiments (n = 18 human observers each), the ball was shown in front of a uniform or a textured background that was either stationary or moved along with the target. Eye and hand movement latencies and speeds were similarly affected by the visual context, but eye and hand interception (eye position at time of interception, and hand interception timing error) did not differ significantly between context conditions. Eye and hand interception timing errors were strongly correlated on a trial-by-trial basis across all context conditions, highlighting the close relation between these responses in manual interception tasks. Our results indicate that visual contexts similarly affect eye and hand movements, but that these effects may be short-lasting, affecting movement trajectories more than movement end points.

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