Performing a task with a friend does not change semantic processes but preparation: A social N400 and CNV event-related potential study

Sujata Sinha ^1,2 Ashley Chau-Morris ^1,2 Milena Kostova ³ J. Bruno Debruille ^1,2*

• ¹ Faculty of Medicine and Health Sciences, McGill University, Montreal, Quebec, Canada
• ² Douglas Mental Health University Institute, Montreal, Quebec, Canada
• ³ Université Paris 8, Saint-Denis, France

The N400 event-related potential (ERP) is an index of the semantic processing of meaningful stimuli, like words. Recently, its amplitude has been found to be larger in the presence of a confederate who was unknown to participants. According to the N400 inhibition hypothesis, these social N400 effects could be due to the automatic sidelining of information that occurs when building a common ground with a stranger. With known persons, like friends, such a common ground already exists. This sidelining does not occur. So, no social N400 should be observed. Here, we report that this is the case whether words were coherent with their context, incoherent or equivocal. Both alones and participants with a friend (PwFs) had to classify them accordingly, at the occurrence of an imperative stimulus following these words. PwFs had larger contingent negative variations (CNVs) than alones, suggesting heightened preparation to this imperative stimulus. Unexpectedly, the larger this effect, the less confident PwFs were in their classifications. Given their higher levels of state anxiety before and after the experiment, it seems that the presence of someone else who completes the same task, even if it is a friend, induces performance pressure, enhancing anxiety and preparation, and diminishing selfconfidence.