Affective Priming Effects by Task-Relevant and Task-Irrelevant Emotional Pictures: An ERP Study

Abstract

The present study examined how task-relevant and task-irrelevant prime stimuli influence the affective priming effect. An emotional picture (unpleasant or neutral) and a checkerboard picture were presented simultaneously as a prime stimulus. Participants were required to pay attention to either the emotional picture (EP-attended condition) or the checkerboard picture (CP-attended condition). An emotionally neutral picture (target) was then presented, and participants were asked to evaluate the emotional valence of the target. The evaluation score was more negative following the unpleasant prime picture, and this priming effect was larger in the EP-attended condition, in which the emotional prime picture was task-relevant than in the CP-attended condition, in which the emotional prime picture was task-irrelevant. The late positive potentials (LPPs) elicited by the prime stimuli were larger when the emotional prime picture was unpleasant, whereas the LPPs elicited by the target stimuli were smaller when the emotional prime picture was unpleasant. More importantly, significant association between the LPP amplitudes and the magnitude of affective priming effects were observed in the EP-attended condition but not in the CP-attended condition. This indicates that the degree of the affective priming effect induced by the task-relevant prime stimulus was related to attentional resource allocation, but this was not the case for the affective priming effect induced by the task-irrelevant prime stimulus. The present results suggest that affective priming effects induced by task-relevant and task-irrelevant prime stimuli occur in a different manner in terms of attentional processing.