Abstract
Cultures, such as Japan, are characterized by tighter or more rigid norms than others, like the United States. However, the mechanism underlying this cultural difference remains unclear. We tested the hypothesis that individuals carrying genetic polymorphisms linked to cultural learning, particularly the 7- or 2-repeat variable number of tandem repeat variants of the dopamine D4 receptor gene, DRD4, would show heightened sensitivity to norm violations if they are from tight cultures but not in loose cultures. A total of 214 Japanese and 236 European American young adults (total N = 450) evaluated the normativity of various behaviors while their electroencephalogram (EEG) was recorded. Consistent with previous findings, norm violations elicited a robust N400 response, an electrocortical marker of expectancy violation. Critically, this N400 norm-violation effect was significantly stronger for Japanese carriers of the DRD4 alleles linked to cultural learning, but no such genetic moderation was observed among European Americans. Moreover, Japanese non-carriers showed a significantly weaker N400 response than their American counterparts. These results suggest that in a tight culture like Japan, heightened neural sensitivity to norm violations may be concentrated among individuals with genetic predispositions for enhanced reward processing, pointing to the dynamic interplay between genetic variations and cultural environments.