People willingly follow norms and values, often incurring material costs. This behaviour supposedly stems from evolved norm psychology, contributing to large-scale cooperation among humans. It has been argued that cooperation is influenced by two types of norms: injunctive and descriptive. This study theoretically explores the socialisation of humans under these norms. Our agent-based model simulates scenarios where diverse agents with heterogeneous norm psychologies engage in collective action to maximise their utility functions that capture three motives: gaining material payoff, following injunctive and descriptive norms. Multilevel selective pressure drives the evolution of norm psychology that affects the utility function. Further, we develop a model with exapted conformity, assuming selective advantage for descriptive norm psychology. We show that norm psychology can evolve via cultural group selection. We then identify two normative conditions that favour the evolution of norm psychology, and therefore cooperation: injunctive norms promoting punitive behaviour and descriptive norms. Furthermore, we delineate different characteristics of cooperative societies under these two conditions and explore the potential for a macro transition between them. Together, our results validate the emergence of large-scale cooperative societies through social norms and suggest complementary roles that conformity and punishment play in human prosociality.

This study examines how beliefs interact with heterogeneous donation preferences in determining people's donation decisions and choices of revision and observability. We conducted an online experiment eliciting participants’ first-order beliefs, that is, beliefs about an average donor's contribution, with the opportunity of being recognized. We also provided the opportunity for donation revision to a group of randomly selected participants. Our study results show that people's first-order beliefs are positively correlated with their willingness to donate and their actual donations. Moreover, first-order beliefs also interact with people's heterogeneous donation preferences in jointly determining their decisions of donation revision and observability – their tendency to opt in for public recognition. Donors with low first-order beliefs and high donation preferences are most likely to opt in for recognition, but they are unlikely to revise their donations. Donors with high first-order beliefs and low donation preferences are most likely to revise their donations, but they are less likely to choose to be recognized. Donors with low first-order beliefs and low donation preferences display the lowest tendency toward revision and observability.

People are more likely to rely on descriptive norms (i.e., what their peers are doing) when deciding whether to take a risk themselves than when deciding whether to recommend others to take a risk. We proposed and found that people also attend to normative information when making risk recommendations to others, but in this case they attend to a different type of normative information — injunctive norms (i.e., whether their peers approve of this behavior). Descriptive norm plays a bigger role in influencing people’s own decisions, whereas injunctive norm plays a bigger role in influencing people’s recommendations to others. This research demonstrates the importance of differentiating descriptive versus injunctive norms in risky decision-making and provides further evidence that perceived norms significantly influence risky decision-making.

Once vaccines against COVID-19 became available in many countries, a new challenge has emerged – how to increase the number of people who vaccinate? Different policies are being considered and implemented, including behaviourally informed interventions (i.e., nudges). In this study, we have experimentally examined two types of nudges on representative samples of two countries – descriptive social norms (Israel) and saliency of either the death experience from COVID-19 or its symptoms (UK). To increase the legitimacy of nudges, we have also examined the effectiveness of transparent nudges, where the goal of the nudge and the reasons of its implementation (expected effectiveness) were disclosed. We did not find evidence that informing people that the vast majority of their country-people intend to vaccinate enhanced vaccination intentions in Israel. We also did not find evidence that making the death experience from COVID-19, or its hard symptoms, salient enhanced vaccination intentions in the UK. Finally, transparent nudges as well did not change the results. We further provide evidence for the reasons why people choose not to vaccinate, and whether different factors such as gender, belief in conspiracy theories, political ideology, and risk perception, play a role in people's intentions to vaccinate or susceptibility to nudges.

This article argues that it is a waste of time seeking to treat populists as examples of homo economicus when seeking to persuade them that the conspiracy theories to which they subscribe are big lies. But it does not follow that homo economicus is worthless in this context. He has a role in explaining the evolution of the social norms whose violation is the root cause of the rise of populist movements. Such an approach requires a willingness to entertain both proximate and ultimate explanations of human behaviour simultaneously.

Institutions can be strong or weak. But what does this mean? Equilibrium theories equate institutions with behavioural regularities. In contrast, rule theories explicate them in terms of a standard that people are supposed to meet. I propose that, when an institution is weak, a discrepancy exists between the regularity and the standard or rule. To capture this discrepancy, I present a hybrid theory, the Rules-and-Equilibria Theory. According to this theory, institutions are rule-governed behavioural regularities. The Rules-and-Equilibria Theory provides the basis for two measures of institutional strength. First, institutions that pertain to coordination games solve problems of information. Their strength is primarily a matter of the expected degree of compliance. Second, institutions that concern mixed-motive games solve problems of motivation. Their strength can be measured in terms of the weight people attribute to its rule.

The scholarly discourse on social norms in the tradition of Thomas Schelling (1960) often makes a sharp distinction between social norms and social conventions. In attempting to apply that distinction to actual practices and to teach it to practitioners and students I encountered frequent difficulties and confusions, and finally concluded that it is untenable. I recommend a return to some version of Ullman-Margalit’s (1977) distinction between social norms of cooperation and social norms of coordination. Social norms, I say, are distinguished by beliefs in a relevant group that the rule is typical among them and approved of among them. I describe four ways that social norms of coordination, including conventions of social meaning, are influenced by social approval and disapproval. I contend that the effort by Southwood and Eriksson (2011) to show that social conventions and social norms are essentially different breaks down because their conception of social norms is overly moralized. I present a more social conception of social norms that does without the regnant distinction between “social norm” and “social convention” and instead allows for social norms of cooperation, social norms of coordination, and other kinds of social norms.

It is crucial for policymakers to focus their attention on social norms if they want to improve policy outcomes, but doing so brings in new normative questions about the appropriate role of the state. Indeed, I argue that efforts to reduce coercion at the state level can create potentially pernicious and difficult to eliminate forms of coercion at the informal level. This creates a new normative challenge for thinking about the broader regulatory apparatus, and complicates our approach in utilizing social norms for democratic policy ends. I will distinguish between two forms of social norms orientations in policy: a diagnostic approach and a design approach. We will see that the diagnostic approach better models a Humean approach to supporting social norms, and a design approach has a more Millian character. While it is easier to justify a design approach in the abstract, as it has very little room for abuses of state authority, if Mill is right that social norms can be a source of coercive power that runs afoul of the harm principle, then a design approach will sometimes be necessary to counter this form of tyranny. However, this latter approach is complex, and as such we may want to take a recommendation from Mockus to focus on deliberative approaches to norm change.