We explore a unifying explanation for prosocial behavior in which people care not about others' payoffs per se, but whether their own behavior accords with social norms. Individuals who are sensitive to norms will adhere to them so long as they observe others doing the same. A model formalizing this generates both prosociality (without relying on explicit distributional preferences) and well-known context effects (for which simple distributional preferences cannot account). A simple experiment allows us to measure individual-level normsensitivity and to show that norm-sensitivity explains heterogeneity in prosociality in public goods, dictator, ultimatum, and trust games.JEL classifications: C91, C92, D03

We explore a unifying explanation for prosocial behavior in which people care not about others' payoffs per se, but whether their own behavior accords with social norms. Individuals who are sensitive to norms will adhere to them so long as they observe others doing the same. A model formalizing this generates both prosociality (without relying on explicit distributional preferences) and well-known context effects (for which simple distributional preferences cannot account). A simple experiment allows us to measure individual-level normsensitivity and to show that norm-sensitivity explains heterogeneity in prosociality in public goods, dictator, ultimatum, and trust games.JEL classifications: C91, C92, D03

This proof of concept study harnesses novel transdisciplinary insights to contrast two school-based smoking prevention interventions among adolescents in the UK and Colombia. We compare schools in these locations because smoking rates and norms are different, in order to better understand social norms based mechanisms of action related to smoking. We aim to: (1) improve the measurement of social norms for smoking behaviors in adolescents and reveal how they spread in schools; (2) to better characterize the mechanisms of action of smoking prevention interventions in schools, learning lessons for future intervention research. The A Stop Smoking in Schools Trial (ASSIST) intervention harnesses peer influence, while the Dead Cool intervention uses classroom pedagogy. Both interventions were originally developed in the UK but culturally adapted for a Colombian setting. In a before and after design, we will obtain psychosocial, friendship, and behavioral data (e.g., attitudes and intentions toward smoking and vaping) from ∼300 students in three schools for each intervention in the UK and the same number in Colombia (i.e., ∼1,200 participants in total). Pre-intervention, participants take part in a Rule Following task, and in Coordination Games that allow us to assess their judgments about the social appropriateness of a range of smoking-related and unrelated behaviors, and elicit individual sensitivity to social norms. After the interventions, these behavioral economic experiments are repeated, so we can assess how social norms related to smoking have changed, how sensitivity to classroom and school year Hunter et al. MECHANISMS Study group norms have changed and how individual changes are related to changes among friends. This Game Theoretic approach allows us to estimate proxies for norms and norm sensitivity parameters and to test for the influence of individual student attributes and their social networks within a Markov Chain Monte Carlo modeling framework. We identify hypothesized mechanisms by triangulating results with qualitative data from participants. The MECHANISMS study is innovative in the interplay of Game Theory and longitudinal social network analytical approaches, and in its transdisciplinary research approach. This study will help us to better understand the mechanisms of smoking prevention interventions in high and middle income settings.

We review the main economic models of war and conflict. These models vary in details, but their implications are qualitatively consistent, highlighting key commonalities across a variety of conflict settings. Recent empirical literature, employing both laboratory and field data, in many cases confirms the basic implications of conflict theory. However, this literature also presents important challenges to the way economists traditionally model conflict. We finish our review by suggesting ways to address these challenges.JEL classifications: D72, D74, F51, F52, F54, H56, N4, Q34

Specialization and exchange are at the core of economics, yet over 230 years after Adam Smith first presented his fundamental theorem, economists know remarkably little about how exchange evolves from personal social interactions-reinforced by local knowledge, reputations, and the prospect of future dealings-to impersonal market transactions undergirded by such formal institutions as impartial courts. Smith, however, merely posited the phenomena of specialization and exchange as an expression of a "propensity in human nature … to truck, barter, and exchange one thing for another," effectively shifting the focus to wealth-creating specialization as a consequence of exchange. Ever since, save the important contributions of economic historians, the evolving process of exchange and specialization has been slighted. Laboratory experiments have mostly examined the efficiency properties of extant institutions or tested new institutions for field application; they have not inquired into the processes that account for the original emergence of market institutions.The general argument from economic history is that informal norms are adequate for smallscale exchange within villages and hunter-gatherer societies, but that as nascent specialization and exchange grow, expanding across a larger area, these informal norms are off-loaded onto more formal, centralized rule systems.Such institutions develop to mitigate the increases in transaction costs resulting from greater possibilities for conflict (Douglass C. North 990, 99;We should emphasize that some exchanges based on the reciprocity and sharing practices of local communities may tend to persist, and not be displaced, by formal centralized rule systems. Thus Robert C. Ellickson (99) provides a case study of the persistence of local norms that ignore codified law in dealing with animal trespass.

Recent models of prosociality suggest that cooperation in laboratory games may be better understood as resulting from concern for social norms than from prosocial preferences over outcomes. Underlying this interpretation is the idea that people exhibit heterogeneous respect for shared norms. We introduce a new, abstract task to elicit a proxy for individual normfollowing propensity by asking subjects to choose from two actions, where one is costly. We instruct subjects that "the rule is" to take the costly action. Their willingness to incur such a cost reveals respect for norms. We show that choices in this task are similar across five countries. Rule-following is correlated with norm-consistent behavior in dictator games, providing support for our interpretation.

By shaping patterns of relatedness and interaction, marriage practices influence the relative returns to norms of nepotism/favoritism versus norms of impartial cooperation. In-marriage (e.g. consanguineous marriage) yields a relatively closed society of related individuals and thereby encourages favoritism and corruption. Out-marriage creates a relatively open society with increased interaction between non-relatives and strangers, thereby encouraging impartiality. We report a robust association between in-marriage practices and corruption across countries and across Italian provinces. A stylized corruption experiment comparing subjects from two countries with divergent marriage patterns provides complementary evidence that the degree of impartiality varies with marriage patterns.

Spiteful, antisocial behavior may undermine the moral and institutional fabric of society, producing disorder, fear, and mistrust. Previous research demonstrates the willingness of individuals to harm others, but little is understood about how far people are willing to go in being spiteful (relative to how far they could have gone) or their consistency in spitefulness across repeated trials. Our experiment is the first to provide individuals with repeated opportunities to spitefully harm anonymous others when the decision entails zero cost to the spiter and cannot be observed as such by the object of spite. This method reveals that the majority of individuals exhibit consistent (non-)spitefulness over time and that the distribution of spitefulness is bipolar: when choosing whether to be spiteful, most individuals either avoid spite altogether or impose the maximum possible harm on their unwitting victims.