Neural correlates of Japanese honorific agreement processing mediated by socio-pragmatic factors: An fMRI study

Socio-pragmatic factors, such as social roles and language experience, could be key variables influencing language processing. However, little is known regarding the neural correlates of syntactic processing mediated by socio-pragmatic factors. Honorific agreement in Japanese is well-suited for the investigation of this issue. Japanese honorifics are governed by socio-pragmatic and syntactic rules. Lower social status speakers are expected to address higher social status counterparts in accordance with these rules. This linguistic skill is typically developed through language experience accrued in social contexts. The present functional magnetic resonance imaging study investigated the neural correlates of the honorific agreement processing mediated by socio-pragmatic factors. Thirty-three native Japanese speakers performed a socio-pragmatic judgment task containing sentence conditions manipulated by conventionality (i.e., conventional vs. unconventional) and speaker (lower-status vs. higher-status). The lower-status conditions elicited significantly more activation of the left inferior frontal gyrus (IFG), bilateral insula, and dorsal medial prefrontal cortex than the higher-status ones, irrespective of conventionality. This suggests that social cues (i.e., speaker social status) trigger computation of honorific agreement via the left IFG. Furthermore, the conventional conditions significantly enhanced activation of the bilateral anterior temporal lobes (ATLs), compared with the unconventional conditions. Finally, the listener's experience with honorific use in the workplace was positively correlated with activation of the left inferior parietal lobule (IPL) during comprehension of conventional honorific utterances. Our findings demonstrate the importance of socio-pragmatic factors in Japanese honorific agreement processing, which involves the ATLs and IPL.