Theories of early cooperation in human society often draw from a small sample of ethnographic studies of surviving populations of hunter–gatherers, most of which are now sedentary. Borneo hunter–gatherers (Punan, Penan) have seldom figured in comparative research because of a decades-old controversy about whether they are the descendants of farmers who adopted a hunting and gathering way of life. In 2018 we began an ethnographic study of a group of still-nomadic hunter–gatherers who call themselves Punan Batu (Cave Punan). Our genetic analysis clearly indicates that they are very unlikely to be the descendants of neighbouring agriculturalists. They also preserve a song language that is unrelated to other languages of Borneo. Dispersed travelling groups of Punan Batu with fluid membership use message sticks to stay in contact, co-operate and share resources as they journey between rock shelters and forest camps. Message sticks were once widespread among nomadic Punan in Borneo, but have largely disappeared in sedentary Punan villages. Thus the small community of Punan Batu offers a rare glimpse of a hunting and gathering way of life that was once widespread in the forests of Borneo, where prosocial behaviour extended beyond the face-to-face community, facilitating successful collective adaptation to the diverse resources of Borneo's forests.

Performing costly helpful behaviours can allow individuals to improve their reputation. Those who gain a good reputation are often preferred as interaction partners and are consequently better able to access support through cooperative relationships with others. However, investing in prosocial displays can sometimes yield social costs: excessively generous individuals risk losing their good reputation, and even being vilified, ostracised or antisocially punished. As a consequence, people frequently try to downplay their prosocial actions or hide them from others. In this review, we explore when and why investments in prosocial behaviour are likely to yield social costs. We propose two key features of interactions that make it more likely that generous individuals will incur social costs when: (a) observers infer that helpful behaviour is motivated by strategic or selfish motives; and (b) observers infer that helpful behaviour is detrimental to them. We describe how the cognition required to consider ulterior motives emerges over development and how these tendencies vary across cultures – and discuss how the potential for helpful actions to result in social costs might place boundaries on prosocial behaviour as well as limiting the contexts in which it might occur. We end by outlining the key avenues and priorities for future research.

Altruism is a universal human trait, but little is known about its within-population variation. Socio-economic status (SES) has been found to positively impact altruism, but the specific socio-economic variables behind this relationship have remained elusive. This study aimed to determine which facets of SES predict altruism using a lost letter paradigm and a novel lost letter method. Six hundred letters (half dropped on the pavement, half sent to residential addresses) were distributed in 20 suburbs of Perth (Australia) differing in socio-economic variables. Letters distributed in high-SES neighbourhoods were more likely to be returned than letters distributed in low-SES neighbourhoods. Educational attainment and occupation status were the specific socio-economic variables underlying this association, while economic resources and crime rate were not associated with the likelihood of a letter being returned. These results suggest that altruism blossoms in neighbourhoods that are populated with highly educated individuals working in high-status jobs. The relationship between education and prosocial inclinations may be mediated by cognitive ability, self-control and high levels of socialization. Having experienced sustained exposure to norm-abiding models, more educated people may also be better at internalizing cultural norms of helping behaviour, thus creating a more altruistic environment where they reside.

An interdependence approach to empathic concern could transform the current societal environment for people with disability into a more accessible and equitable one. To our knowledge, this is the first study to investigate two possible factors influencing empathic concern, gender and ethnic culture, in specific helping scenarios. We first examined whether the female gender and collectivist culture of Japan were associated with higher levels of interdependence and empathic concern for disability than were the male gender and individualist culture of New Zealand. Empathic concern for people with impairment was assessed in accessible and inaccessible environments. Neither gender nor culture significantly influenced the level of interdependence, whereas gender and culture differentially moderated empathic concern. We also explored the possibility of altering self-construal and thus promoting prosocial behaviour by examining the correlation between self-construal and prosocial intention, and the effect of cultural priming on self-construal. The correlation was significant under inaccessible conditions in the Japanese sample, and the effect of interdependent priming was not significant on interdependent self-construal in both countries. Discussion centres on theoretical implications of the observed conditional support for the female-gender and collectivist-culture hypotheses, and on ways to promote prosocial behaviour, taking into account gender and cultural differences.

There is a small, but growing, body of research investigating peer-victimisation between preschoolers, an age which has been identified as being important both theoretically and practically for the development of interventions. This study compares aggressive and defending behaviour and victim status of preschoolers in three European countries; England, Spain and Italy. The results provide further confirmation that some children behave aggressively towards their peers during preschool in each of the countries studied. There are similarities between preschool children involved in peer-victimisation in the three countries in terms of the roles taken, sex differences and the types of aggressive behaviours used and experienced by the children. There were differences in the profiles of children identified as taking the roles by teachers and peers. Overall, it was found that those children identified by peers or teachers as being aggressive were more likely to be male, rated as physically strong and more likely to be rejected by classmates. Also, in general, the targets of peer-victimisation differed depending on the reporter. Peer-nominated victims were not identifiable in terms of gender, popularity or physical strength. Teacher-nominated victims were more likely to be socially rejected and physically weak. There are several subtle differences between the countries which deserve further investigation. The findings are discussed in relation to furthering our understanding of the development of peer-victimisation in preschools and the need for interventions which address this phenomenon.

We tested a model of prosocial development, which predicted that prosocial action might decline, not increase, throughout childhood, becoming increasingly selective, individual, gender-related, and linked to emotional dysregulation. Sixty-six focal children at 18, 24, or 30 months of age were observed at home with familiar peers and then again 6 months later. Episodes of peer interaction were analysed for instances of sharing. The predicted decline in sharing with age was qualified by cohort differences and many associations with gender. Most children shared less as they grew older, but the oldest girls slightly increased their rate of sharing over time. As peer relationships developed, girls were more likely to share with other girls; boys were more likely to show reciprocity in sharing. Individual differences in sharing were moderately stable over time and linked to another form of prosocial action, sensitivity to the peer's distress. As predicted, children who shared at higher rates were rated more negatively by their mothers. The positive relationship between prosocial action and mothers' ratings of negative personality traits was especially strong for boys.