Please be logical, I am in a bad mood: An electrophysiological study of mood effects on reasoning.

Several behavioral studies have reported a detrimental effect of emotion on reasoning tasks, either when the content of the reasoning and/or the mood state of the individual are emotionally loaded. However, the neural mechanisms involved in this phenomena remain largely unexplored. In an event-related potentials (ERPs) study, we examined the consequences of an induced mood over the electrophysiological signals obtained while processing logical and illogical categorical conclusions. Prior to performing a syllogism reading task, we aimed to induce, by using short film clips, high arousal negative and positive moods and neutral affective states to participants in three separate recording sessions. Our mood induction procedure was only successful at inducing a highly arousing negative state. Behaviorally, participants committed more errors overall while judging the invalidity versus the validity of illogical and logical conclusions, respectively, but no influences from mood state emerged at this logical validity task. Electrophysiologically and overall a negative going N400 deflection was larger for illogical relative to logical conclusions in a parietal region between 300 and 420 ms. However, further analysis revealed that the logical conclusions were only more expected (smaller N400 amplitudes) in the negative relative to the neutral and the positive sessions, providing support to theoretical views that posit that a more analytic reasoning style might be implemented under a negative mood state. These results provide further electrophysiological evidence of the influence of mood on other cognitive processes, particularly on the anticipation and processing of logical conclusions during online reasoning tasks.