Distractors that signal reward attract the eyes

Salient stimuli and stimuli associated with reward have the ability to attract both attention and the eyes. The current study exploited the effects of reward on the well-known global effect in which two objects appear simultaneously in close spatial proximity. Participants always made saccades to a predefined target, while the colour of a nearby distractor signalled the reward available (high/low) for that trial. Unlike previous reward studies, in the current study these distractors never served as targets. We show that participants made fast saccades towards the target. However, saccades landed significantly closer to the high compared to the low reward signalling distractor. This reward effect was already present in the first block and remained stable throughout the experiment. Instead of landing exactly in between the two stimuli (i.e., the classic global effect), the fastest eye movements landed closer towards the reward signalling distractor. Results of a control experiment, in which no distractor-reward contingencies were present, confirmed that the observed effects were driven by reward and not by physical salience. Furthermore, there were trial-by-trial reward priming effects in which saccades landed significantly closer to the high instead of the low reward signalling distractor when the same distractor was presented on two consecutive trials. Together the results imply that a reward signalling stimulus that was never part of the task set has an automatic effect on the oculomotor system.