Reinforcement learning of altruistic punishment differs between cultures and across the lifespan
Fig 2
Cultural and group influences on altruistic punishment behavior in pre-test and reinforcement learning stages.
A Pre-test stage: Chinese participant exhibited stronger ingroup bias compared to American participants. Overall, participants punished ingroup (green) more severely compared to outgroup (orange) dividers. However, Chinese participants exhibited an enhanced group bias (b = - 0.82, SE = 0.29, z = -2.94, p = .003). B Reinforcement learning stage: when acceptance was rewarded, Chinese participants punished ingroup dividers (green) less severely compared to outgroup dividers (b = -0.91, SE = 0.23, z = -4.06, p < .001), no significant differences were found between punishment towards ingroup and outgroup dividers among American participants (b = -0.20, SE = 0.26, z = -0.76, p = .871). C Reinforcement learning stage: when punishment was rewarded, Chinese participants punished ingroup dividers (green) less severely compared to outgroup dividers (b = -0.87, SE = 0.22, z = -4.01, p < .001), no significant differences were found between punishment towards ingroup and outgroup dividers among American participants (b = -0.61, SE = 0.26, z = -2.37, p = .084). D Group level trial-by-trial punishment rates in the two divider conditions (ingroup: green, outgroup: orange) for each culture group (Chinese: squares, American: circles). Points represent group mean; error bars are standard errors. E Regardless of whether punishment or acceptance was rewarded, Chinese participants had lower learning rates for ingroup norms (b = -0.07, SE = 0.01, t = -5.51, p < .001), while American participants showed no differences (b = -0.02, SE = 0.01, t = -1.46, p = .460). F Regardless of whether punishment or acceptance was rewarded, Chinese participants had lower β when learning ingroup norms (b = -0.23, SE = 0.04, t = -5.85, p < .001), while no differences were observed for American participants (b = -0.08, SE = 0.04, t = -1.90, p = .231). G Chinese participants showed a stronger bias compared to American participants, especially when punishment was rewarded (MDiff = 0.06, SE = .01, t = 5.11, p < .001). Error bars represent standard errors. * p < .05, *** p < .001.