Context Matters: Hyperscanning the N400 Lexical Frequency Effect during Scripted Conversation and Passive Listening

ERP studies of lexical processing typically involve individuals perceiving isolated words or sentences. However, much of language processing occurs in conversation with others. Here, we used EEG hyperscanning while pairs of acquaintances either engaged in a scripted conversation or passively viewed a recording of the scripted conversation. Our primary goals were to replicate the established N400 frequency effect (a greater negativity between ∼300 and 600 msec for low-frequency words) and compare this effect during scripted conversation to passive viewing, which more closely resembled conventional paradigms. Target words of high and low lexical frequency were embedded in the dialogues, and the onsets of these words were identified post hoc from audio synchronized with the EEG data. Both groups exhibited a significantly greater N400 response when hearing low-frequency words compared with high-frequency words, replicating previous findings. However, the N400 frequency effect was significantly larger in the control group than in the scripted conversation group across midline central-parietal channels. This attenuation in the scripted conversation condition may reflect differences in lexical processing in the context of active social interaction compared with passive comprehension. Specifically, the rapport created by engaging in a conversation with another person may facilitate lexical access and reduce the greater processing associated with low-frequency words. These findings demonstrate that ERP experiments can be conducted using conversational stimuli, opening new opportunities to study real-time language processing in interactive social contexts.