Reinforcement learning of altruistic punishment differs between cultures and across the lifespan
Fig 4
Age-related differences in ingroup bias and learning mechanisms among Chinese individuals.
A Pre-test stage: the interaction effect between age and dividers’ group reveals a decrease in punishing unfair ingroup dividers (blue) with increasing age (b = -0.03, SE = 0.02, z = -2.05, p = .040), while punishment rates for outgroup dividers (purple) remain unchanged (b = -0.01, SE = 0.02, z = -0.34, p = .734). B Reinforcement learning stage: younger participants’ behavioral responses toward ingroups were more consistent with the norms than were older participants: when acceptance was rewarded, younger participants exhibited less punishment compared to older individuals (b = 0.03, SE = 0.02, z = 2.32, p = .020); when punishment was rewarded, younger participants exhibited more punishment than older participants b = -0.03, SE = 0.02, z = -1.51, p = .131). By contrast, the age differences were not significant for unfair outgroup dividers under either social feedback condition. C Trial-by-trial punishment rates for ingroup (blue) and outgroup (purple) dividers across age groups (adolescents: squares, adults: circles). Points represent group mean, and error bars are standard errors. D learning rate (α) for punishing unfair ingroups decreased with age (b = -0.14, SE = 0.03, t = -4.21, p < .001), while the α for punishing outgroups was not associated with age (b = -0.02, SE = 0.03, t = -0.68 p = .500). E Temperature (beta): Lower β for learning ingroup norms than outgroup norms regardless of age (b = -0.25, SE = 0.05, t = -5.36, p < .001); β decreased with age (b = -0.12, SE = 0.04, t = -2.74, p = .006). F the bias term significantly increased with age regardless of punishment norms (b = 0.13, SE = 0.05, t = 2.65, p = .008). Error bars represent standard errors. * p < .05. ** p < .01. *** p < .001.