Being only with yourself enhances the binding of stimulus representations with both egocentric- and allocentric-representations of the self: A P2 event-related potential study.

Perceiving a stimulus involves the awareness that it is we who are perceiving it. Representations activated by the stimulus are thus automatically bound to representations of the self. Interestingly, previous research has shown that the amplitude of the P2 event-related brain potential (ERP) is larger for stimuli to which participants can refer themselves. This suggests that the P2 may index the binding of stimulus representations with self-representations and that this binding is modulable, like other automatic processes. P2 amplitudes could then be larger in participants who are only with themselves than in those with a friend (PwFs). Consistently, we found larger P2s in alones (n = 53) than in PwFs (n = 47) at two scalp locations. Firstly, at the midline central electrode, where large self-referencing effects were previously observed, indicating stronger binding with egocentric self-representations. Secondly, at the left temporo-occipital sites, suggesting stronger allocentric self-representation binding. Furthermore, these P2 effects were maximal for words with richer meanings, that is, for equivocal ones, intermediate for unequivocal-, and minimal for meaningless stimuli. P2 amplitude was thus modulated not only by current self-representations but also by stimulus representations, in accordance with the idea that it indexes their binding.