5-HTTLPR polymorphism and impulsivity under punishment: a gene × culture interaction

A previous Japanese study has shown that the short (s) allele of the serotonin-transporter-linked polymorphic region (5-HTTLPR), implicated in higher sensitivity to aversive stimuli, may promote motor inhibitory control in conditions where impulsivity is punished. The present study conducted in Australia replicates this Japanese study to examine if culture modulates the observed gene–behaviour link. Japan has a tight culture, where norm adherence and low impulsivity are emphasised. In contrast, Australia is a loose culture, where deviation from norms is tolerated to a greater extent. We therefore expected that the s-allele carriers’ strong motor inhibitory control in aversive conditions might be weaker in Australia than in Japan. Ninety-eight second-generation Australians of East Asian heritage, including 53s/s-allele carriers, 32s/l-allele carriers and 11l/l-allele carriers, participated in the reward/punishment-go/nogo task. As expected, s/s carriers in Australia, compared with their peers in Japan, showed higher impulsivity when inappropriate responding was punished (i.e. punishment-nogo conditions) but lower impulsivity when appropriate non-responding was rewarded (i.e. reward-nogo conditions). In contrast, the behaviours of the Australian s/l-allele carriers were similar to those of their Japanese counterparts. The results suggest that the larger context of culture that provides behavioural norms should be considered when examining gene × environment interaction.