Uncertainty-modulated attentional capture: Outcome variance increases attentional priority

Previous research has shown that attentional priority is influenced by prior learning about reward magnitude: signals of high reward value are more likely to capture attention (and gaze) than signals of low reward value. We show in three experiments that attentional priority is also modulated by the uncertainty associated with that reward. Participants completed a visual search task in which they had to make a saccade to a target shape to earn monetary reward. The colour of a colour-singleton distractor in the search array signalled the reward outcome(s) that were available, with different distractor colours being associated with different degrees of variance and expected value in reward outcome. Participants were never required to look at the coloured distractor, and doing so would slow their response to the target. Nevertheless, participants often made eye-movements towards the distractor, and across all experiments they were more likely to look at distractors associated with high outcome variance versus low outcome variance. This pattern was observed when all distractors had equal expected value (Experiment 1), when the difference in variance was opposed by a difference in expected value (i.e., the high-variance distractor had low expected value, and vice versa: Experiment 2), and when distractors were matched for their association with the maximum value outcome (Experiment 3). Our results suggest that outcome variance plays a critical role in modulating rapid attentional and oculomotor priority. More generally, these findings challenge theoretical accounts arguing that the attentional priority of a stimulus is driven by its ability to resolve current uncertainty, and suggest instead that priority is driven by the potential for a stimulus to reduce future uncertainty through a process of learning.