Cross-cultural differences in prefrontal cortex activity in moral judgment: A functional near-infrared spectroscopy (fNIRS) study based on the CNI model

Background: In the past, comparative cultural neurological studies of moral judgments have mainly focused on Eastern and Western groups. We initially examined Japanese and Chinese groups, both East Asian cultures. We utilized a recently proposed polynomial model known as the "consequences, norms, and generalized inaction" (CNI) model to investigate the variations in the overall prefrontal cortex activity between these two groups during moral judgment. Methods: We employed functional near -infrared spectroscopy (fNIRS) to analyze the prefrontal cortex (PFC) activity within a CNI model of moral judgment among 23 healthy Japanese and 26 healthy Chinese adults. Results and Conclusions: Our study revealed significant differences in the PFC activation between Japanese and Chinese individuals in the CNI moral judgment task context. Specifically, during the CNI task, Chinese men exhibited higher right dorsolateral prefrontal cortex (R-DLPFC) activity than Chinese women. In contrast, Japanese women showed greater left dorsolateral prefrontal cortex (L-DLPFC) activity than Japanese men. In an international comparison, R-DLPFC activity was higher in Chinese men than in Japanese men. Conversely, the left ventrolateral prefrontal cortex activity was higher in Japanese men compared to Chinese men. Additionally, among women, the right ventromedial prefrontal cortex activity was higher in Japanese women than in Chinese women. In conclusion, our findings support the perspective of cultural psychology and identify cultural and sex differences in PFC activity between Japanese and Chinese individuals.