Activation of the Motor System Following Gaze Cues is Determined by Hand Access, Not Hand Proximity

Previous research revealed that the influence of gaze cues on target prioritization and movement execution (indexed by reaction times (RTs) and movement trajectories, respectively) differ based on the potential ability of the gaze cue model to interact with the targets. Notably, whereas gaze cues consistently impacted RTs, movement trajectories may only be affected when the hands of the gaze cue model had the potential to interact with the target. However, the perceived ability to interact with the targets was confounded by the proximity between the model’s hands and the targets. The current study was designed to determine if the influence of gaze cues on movement trajectories is shaped by the model’s potential to access and interact with the targets, or by hand proximity. A centrally-presented model randomly gazed towards one of two peripheral target locations. Participants executed aiming movements to targets that non-predictively appeared at one location at a stimulus onset asynchrony of 100, 350, or 850 ms. The model’s hands were either oriented palms-upwards while holding a tray (hands could not directly access the targets; Experiment 1) or palms-downwards in a wrist-flexed posture (hands had direct access to the targets; Experiment 2). Although RTs showed a facilitation effect of the gaze cue in both experiments, changes in movement trajectories were only observed when the model had direct access to the target (Experiment 2). The results of the current study suggest that the gaze model’s direct hand access is necessary for the social gaze cues to influence movement execution.