Attentional capture by Pavlovian reward-signalling distractors in visual search persists when rewards are removed

Existing research indicates that learning about the Pavlovian 'signal value' of stimuli can induce attentional biases: findings suggest that our attentional system prioritises detection of stimuli that have previously signalled availability of high reward. These findings potentially provide a human analogue of sign-tracking behaviour previously reported in studies of non-human animals. Here we examine a visual search task that has been developed to demonstrate the Pavlovian influence of reward on attention, in which the critical reward-signalling stimuli are never explicit targets of search. This procedure has previously yielded robust effects of reward on attention; however it remains unclear whether this pattern reflects a persistent and automatic bias in attentional capture based on prior experience of stimulus-reward pairings, or whether it results from participants strategically attending to reward-signalling distractors because they provide useful information about reward magnitude. To investigate this issue, in the current study participants initially completed a rewarded visual search task, in which colours of distractor stimuli signalled availability of high or low reward. Participants then completed a test phase in which rewards were no longer available, such that distractor colours no longer provided useful information on reward availability. Performance during the initial rewarded phase was impaired by the presence of a distractor signalling availability of high relative to low reward. Crucially, the magnitude of this reward-related distraction effect did not reduce in the subsequent unrewarded test phase. This suggests that participants' experience of differences in reward value signalled by distractor stimuli in this task can induce persistent biases in the extent to which these stimuli involuntarily capture attention, even when they are entirely task-irrelevant.