Abstract
When presented with a set of possible reach targets, movement trajectories can reveal aspects of the underlying competition for action selection. (i) Stimuli associated with reward have been shown to attract reaching movements when the reward stimuli were physically salient and reaching to them was previously rewarded. In the first study, participants had to reach towards a target diamond shape surrounded by differently colored distractor circles. On some trials the color of one of the distractors signaled the availability of earning either low or high reward. The results showed that stimuli that signal high reward attract reaching movements. This effect was particularly pronounced for short latency movements. We concluded that stimuli signaling the availability of earning reward gain priority during the selection for action even when the reward stimulus is non-physically salient and reaching towards them was never rewarded nor necessary. (ii) Furthermore, physically salient distractors typically attract reaching movements. Previous studies on covert and overt attention showed that, under certain top-down task sets, a physically salient distractor can be quickly suppressed to avoid capture. However, it is unclear whether active suppression also occurs during reaching movement planning. In the second study, participants were asked to reach towards a target diamond shape surrounded by distractor circles. All shapes could be in the same color or one of the distractor shapes could be in a physically salient color. In one session participants had to search the reach target; in another session the reach target was cued. The results showed that the highly physically salient distractor attracted reaching movements performed to the searched target but not to the cued target. We conclude that the priority towards physically salient stimuli during selection for action can be actively suppressed under certain top-down task sets, avoiding attraction.