Modelling social norms: an integration of the norm-utility approach with beliefs dynamics

Signals of belonging: emergence of signalling norms as facilitators of trust and parochial cooperation

Mechanisms of social control reinforce norms that appear harmful or wasteful, such as mutilation practises or extensive body tattoos. We suggest such norms arise to serve as signals that distinguish between ingroup 'friends' and outgroup 'foes', facilitating parochial cooperation. Combining insights from research on signalling and parochial cooperation, we incorporate a trust game with signalling in an agent-based model to study the dynamics of signalling norm emergence in groups with conflicting interests. Our results show that costly signalling norms emerge from random acts of signalling in minority groups that benefit most from parochial cooperation. Majority groups are less likely to develop costly signalling norms. Yet, norms that prescribe sending costless group identity signals can easily emerge in groups of all sizes-albeit, at times, at the expense of minority group members. Further, the dynamics of signalling norm emergence differ across signal costs, relative group sizes, and levels of ingroup assortment. Our findings provide theoretical insights into norm evolution in contexts where groups develop identity markers in response to environmental challenges that put their interests at odds with the interests of other groups. Such contexts arise in zones of ethnic conflict or during contestations of existing power relations. This article is part of the theme issue 'Social norm change: drivers and consequences'.

Jeans and language: kin networks and reproductive success are associated with the adoption of outgroup norms

Traditional norms of human societies in rural China may have changed owing to population expansion, rapid development of the tourism economy and globalization since the 1990s; people from different ethnic groups might adopt cultural traits from outside their group or lose their own culture at different rates. Human behavioural ecology can help to explain adoption of outgroup cultural values. We compared the adoption of four cultural values, specifically speaking outgroup languages/mother tongue and wearing jeans, in two co-residing ethnic groups, the Mosuo and Han. Both groups are learning outgroup traits, including each other's languages through contact in economic activities, education and kin networks, but only the Mosuo are starting to lose their own language. Males are more likely to adopt outgroup values than females in both groups. Females of the two groups are no different in speaking Mandarin and wearing jeans, whereas males do differ, with Mosuo males being keener to adopt them than Han males. The reason might be that Mosuo men experience more reproductive competition over mates, as Mosuo men have larger reproductive skew than others. Moreover, Mosuo men but not others gain fitness benefits from the adoption of Mandarin (they start reproducing earlier than non-speakers). This article is part of the theme issue 'Social norm change: drivers and consequences'.

Social norm change: drivers and consequences

Social norms research is booming. In recent years, several experts have recommended using social norms (unwritten rules that prescribe what people ought or ought not to do) to confront the societal, environmental and health challenges our societies face. If we are to do so, a better understanding is required of how social norms themselves emerge, evolve and respond to these challenges. Social norms have long been used as post hoc explanations of behaviour or are seen as stable social constructs. Yet norms evolve dynamically with the changing group processes (e.g. political polarization, kinship structures) and societal challenges (e.g. pandemics, climate change) for which they are presented as solutions. The Theme Issue 'Social norm change: drivers and consequences' contains 14 contributions that present state-of-the-art approaches to understand what generates social norm change and how this impacts our societies. Contributions give insight into (i) the identification of norms, norm change and their effect on behaviour; (ii) drivers and consequences of spontaneous norm change; and (iii) how norm change can be engineered to promote desired behavioural change. This article is part of the theme issue 'Social norm change: drivers and consequences'.

Cross-societal variation in norm enforcement systems

Across human societies, people are sometimes willing to punish norm violators. Such punishment can take the form of revenge from victims, seemingly altruistic intervention from third parties, or legitimized sanctioning from institutional representatives. Although prior work has documented cross-cultural regularities in norm enforcement, substantial variation exists in the prevalence and forms of punishment across societies. Such cross-societal variation may arise from universal psychological mechanisms responding to different socio-ecological conditions, or from cultural evolutionary processes, resulting in different norm enforcement systems. To date, empirical evidence from comparative studies across diverse societies has remained disconnected, owing to a lack of interdisciplinary integration and a prevalent tendency of empirical studies to focus on different underpinnings of variation in norm enforcement. To provide a more complete view of the shared and unique aspects of punishment across societies, we review prior research in anthropology, economics and psychology, and take a first step towards integrating the plethora of socio-ecological and cultural factors proposed to explain cross-societal variation in norm enforcement. We conclude by discussing how future cross-societal research can use diverse methodologies to illuminate key questions on the domain-specificity of punishment, the diversity of tactics supporting social norms, and their role in processes of norm change. This article is part of the theme issue 'Social norm change: drivers and consequences'.

When norm change hurts

Applied cultural evolution includes any effort to mobilize social learning and cultural evolution to promote behaviour change. Social tipping is one version of this idea based on conformity and coordination. Conformity and coordination can reinforce a harmful social norm, but they can also accelerate change from a harmful norm to a beneficial alternative. Perhaps unfortunately, the link between the size of an intervention and social tipping is complex in heterogeneous populations. A small intervention targeted at one segment of society can induce tipping better than a large intervention targeted at a different segment. We develop and examine two models showing that the link between social tipping and social welfare is also complex in heterogeneous populations. An intervention strategy that creates persistent miscoordination, exactly the opposite of tipping, can lead to higher social welfare than another strategy that leads to tipping. We show that the potential benefits of miscoordination often hinge specifically on the preferences of people most resistant to behaviour change. Altogether, ordinary forms of heterogeneity complicate applied cultural evolution considerably. Heterogeneity weakens both the link between the size of a social planner's intervention and behaviour change and the link between behaviour change and the well-being of society. This article is part of the theme issue 'Social norm change: drivers and consequences'.