Getting Close: Proximity of the Hands Affects Target Prioritization and Movement Execution in the Gaze Cueing Paradigm

Humans are influenced by social cues. Previous research has demonstrated that eye gaze can alter target prioritization (reaction time, RT). Specifically, when cued gaze direction is congruent with target locations, there is an increase in prioritization (facilitation) at short cue-target asynchronies and a decrease in prioritization (inhibition) in manual reaching tasks. Previous research has also suggested that when action was implied by the hand position of the gaze model relative to the targets, manual aiming movements were impacted. Specifically, movement trajectories were differentially affected when the gaze model appeared prepared to grasp the targets versus having their arms crossed. However, this previous work did not disassociate the model’s action potential from their hands’ proximity to the target. Thus, the present work aimed to disentangle a proximity-based account and an action potential-based account and their effects on movement execution. The same gaze model as in previous studies was used, positioned with his arms extended beneath the targets and hands facing downward (so there was no potential to act). Participants performed manual reaching tasks while following a nonpredictive gaze cue, including three variations in stimulus onset asynchrony (SOA). RT analysis showed a facilitation effect at 350 ms SOA, but no cueing effects at 100 ms or 850 ms SOA. Trajectory analysis showed similar facilitation effects at 350 SOA, but no significant deviations at other SOAs. The results suggest that the proximity of the hands may elicit the facilitation effect in movement execution, instead of the potential to act on the targets.