Résumé
Many daily activities are comprised of sequences of smaller motions, but how actions influence those preceding them remains unclear. Behaviourally, the end-state comfort effects reveals that costly actions are undertaken if they terminate in an ideal state for subsequent action. Beyond motivating their selection, subsequent actions appear to interfere in planning of prior ones, e.g., when reaching to the first of two dowels, wrist orientation is biased toward that of the latter dowel (Hesse & Deubel, 2010). This interference might not be limited to anticipated follow-ups, but also those representing possible present actions: when begun prior to target reveal, reach trajectories reliably vector toward the "average" target location until the actual target is signaled (Chapman et al., 2010, 2014). Herein we explored whether future reaches might similarly interfere with present ones. Participant made two reach-to-touch motions: first, from a start circle to a central circle directly ahead, then to either a left or right circle placed further ahead. Between blocks, we varied whether the final target (left or right) was visibly present during the initial centre-out reach, or revealed upon touching centre. Across "delayed" blocks, we varied to which side targets would likely appear, for "immediate" blocks location was equiprobable. Our key metric was left/right deviation in initial centre-out reaches. Generally, reliable deviations were observed toward delayed targets' likely location, whereas immediately visible targets' actual position exerted little influence. Results are related to an ongoing debate within GBYK literature, regarding whether trajectory "averaging" is a result of interference, or strategy.
