Reward expectation modulates multiple stages of auditory conflict control

Although mounting evidence has shown that reward can improve conflict control in the visual domain, little is known about whether and how reward affects conflict processing in the auditory domain. In the present study, we adopted an auditory Stroop task in which the meaning of a sound word ('male' or 'female') could be either congruent or incongruent with the gender of the voice (male or female speaker), and the participants were asked to discriminate the gender of the voice (the phonetic task) or the meaning of the word (the semantic task). Importantly, an auditory cue signalling a potential reward or no-reward for the current trial was presented prior to the sound word. In both tasks, relative to the congruent sound word, response to the incongruent sound word was delayed, i.e., an auditory Stroop effect. However, this auditory Stroop effect was reduced following a reward cue relative to a no-reward cue. Event-related potentials (ERPs) showed a stronger contingent negativity variation (CNV, 1000-1500 ms) for the reward cue than for the no-reward cue. The conflict negativity N_inc (300-400 ms) was more negative-going for the incongruent word than for the congruent word, but this effect was significantly reduced in the reward condition. However, the late positive complex (LPC) showed at most a weak reward modulation. These findings suggest that reward expectation improves auditory conflict control by modulating different stages of conflict processing: promoting better attentional preparation for the upcoming target (CNV), and facilitating conflict detection (N_inc) on the presentation of the target.