The influence of motivational salience on saccade latencies.

Eye movements provide a direct link to study the allocation of overt attention to stimuli in the visual field. The initiation of saccades towards visual stimuli is known to be influenced by the bottom-up salience of stimuli as well as the motivational context of the task. Here, we asked whether the initiation of saccades is also influenced by the intrinsic motivational salience of a stimulus. Face stimuli were first associated with positive or negative motivational salience through instrumental learning. The same faces served as target stimuli in a subsequent saccade task, in which their motivational salience was no longer task-relevant. Participants performed either voluntary saccades, which required the selection of the saccade target out of two simultaneously presented stimuli (experiment 1), or reactive saccades, where only the target stimulus was presented (experiment 2). We found a specific effect of learned positive stimulus value on the latencies of voluntary saccades: For faces with high versus low positive motivational salience, saccadic latencies were significantly reduced. No such difference was observed for previously punished faces. In contrast, reactive saccades to both previously rewarded and punished faces were unaffected by learned stimulus value. Our findings show for the first time that saccadic preparation is susceptible to the acquired intrinsic motivational salience of visual stimuli. Based on the observation that only voluntary saccades but not reactive saccades were modulated, we conclude that the recruitment of neural processes for target identification is required to allow for an influence of motivational stimulus salience on saccadic preparation.