A synthesis of evidence for policy from behavioural science during COVID-19.

Scientific evidence regularly guides policy decisions1, with behavioural science increasingly part of this process2. In April 2020, an influential paper3 proposed 19 policy recommendations ('claims') detailing how evidence from behavioural science could contribute to efforts to reduce impacts and end the COVID-19 pandemic. Here we assess 747 pandemic-related research articles that empirically investigated those claims. We report the scale of evidence and whether evidence supports them to indicate applicability for policymaking. Two independent teams, involving 72 reviewers, found evidence for 18 of 19 claims, with both teams finding evidence supporting 16 (89%) of those 18 claims. The strongest evidence supported claims that anticipated culture, polarization and misinformation would be associated with policy effectiveness. Claims suggesting trusted leaders and positive social norms increased adherence to behavioural interventions also had strong empirical support, as did appealing to social consensus or bipartisan agreement. Targeted language in messaging yielded mixed effects and there were no effects for highlighting individual benefits or protecting others. No available evidence existed to assess any distinct differences in effects between using the terms 'physical distancing' and 'social distancing'. Analysis of 463 papers containing data showed generally large samples; 418 involved human participants with a mean of 16,848 (median of 1,699). That statistical power underscored improved suitability of behavioural science research for informing policy decisions. Furthermore, by implementing a standardized approach to evidence selection and synthesis, we amplify broader implications for advancing scientific evidence in policy formulation and prioritization.

Explaining the evolution of gossip.

Gossip, the exchange of personal information about absent third parties, is ubiquitous in human societies. However, the evolution of gossip remains a puzzle. The current article proposes an evolutionary cycle of gossip and uses an agent-based evolutionary game-theoretic model to assess it. We argue that the evolution of gossip is the joint consequence of its reputation dissemination and selfishness deterrence functions. Specifically, the dissemination of information about individuals' reputations leads more individuals to condition their behavior on others' reputations. This induces individuals to behave more cooperatively toward gossipers in order to improve their reputations. As a result, gossiping has an evolutionary advantage that leads to its proliferation. The evolution of gossip further facilitates these two functions of gossip and sustains the evolutionary cycle.

Multilevel cultural evolution: From new theory to practical applications.

Evolutionary science has led to many practical applications of genetic evolution but few practical uses of cultural evolution. This is because the entire study of evolution was gene centric for most of the 20th century, relegating the study and application of human cultural change to other disciplines. The formal study of human cultural evolution began in the 1970s and has matured to the point of deriving practical applications. We provide an overview of these developments and examples for the topic areas of complex systems science and engineering, economics and business, mental health and well-being, and global change efforts.

Norm Dynamics: Interdisciplinary Perspectives on Social Norm Emergence, Persistence, and Change.

Social norms are the glue that holds society together, yet our knowledge of them remains heavily intellectually siloed. This article provides an interdisciplinary review of the emerging field of norm dynamics by integrating research across the social sciences through a cultural-evolutionary lens. After reviewing key distinctions in theory and method, we discuss research on norm psychology-the neural and cognitive underpinnings of social norm learning and acquisition. We then overview how norms emerge and spread through intergenerational transmission, social networks, and group-level ecological and historical factors. Next, we discuss multilevel factors that lead norms to persist, change, or erode over time. We also consider cultural mismatches that can arise when a changing environment leads once-beneficial norms to become maladaptive. Finally, we discuss potential future research directions and the implications of norm dynamics for theory and policy.

When danger strikes: A linguistic tool for tracking America's collective response to threats.

In today's vast digital landscape, people are constantly exposed to threatening language, which attracts attention and activates the human brain's fear circuitry. However, to date, we have lacked the tools needed to identify threatening language and track its impact on human groups. To fill this gap, we developed a threat dictionary, a computationally derived linguistic tool that indexes threat levels from mass communication channels. We demonstrate this measure's convergent validity with objective threats in American history, including violent conflicts, natural disasters, and pathogen outbreaks such as the COVID-19 pandemic. Moreover, the dictionary offers predictive insights on US society's shifting cultural norms, political attitudes, and macroeconomic activities. Using data from newspapers that span over 100 years, we found change in threats to be associated with tighter social norms and collectivistic values, stronger approval of sitting US presidents, greater ethnocentrism and conservatism, lower stock prices, and less innovation. The data also showed that threatening language is contagious. In all, the language of threats is a powerful tool that can inform researchers and policy makers on the public's daily exposure to threatening language and make visible interesting societal patterns across American history.

From virility to virtue: the psychology of apology in honor cultures.

In honor cultures, relatively minor disputes can escalate, making numerous forms of aggression widespread. We find evidence that honor cultures' focus on virility impedes a key conflict de-escalation strategy-apology-that can be successfully promoted through a shift in mindset. Across five studies using mixed methods (text analysis of congressional speeches, a cross-cultural comparison, surveys, and experiments), people from honor societies (e.g., Turkey and US honor states), people who endorse honor values, and people who imagine living in a society with strong honor norms are less willing to apologize for their transgressions (studies 1-4). This apology reluctance is driven by concerns about reputation in honor cultures. Notably, honor is achieved not only by upholding strength and reputation (virility) but also through moral integrity (virtue). The dual focus of honor suggests a potential mechanism for promoting apologies: shifting the focus of honor from reputation to moral integrity. Indeed, we find that such a shift led people in honor cultures to perceive apologizing more positively and apologize more (study 5). By identifying a barrier to apologizing in honor cultures and illustrating ways to overcome it, our research provides insights for deploying culturally intelligent conflict-management strategies in such contexts.

The pandemic exposes human nature: 10 evolutionary insights.

Humans and viruses have been coevolving for millennia. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, the virus that causes COVID-19) has been particularly successful in evading our evolved defenses. The outcome has been tragic-across the globe, millions have been sickened and hundreds of thousands have died. Moreover, the quarantine has radically changed the structure of our lives, with devastating social and economic consequences that are likely to unfold for years. An evolutionary perspective can help us understand the progression and consequences of the pandemic. Here, a diverse group of scientists, with expertise from evolutionary medicine to cultural evolution, provide insights about the pandemic and its aftermath. At the most granular level, we consider how viruses might affect social behavior, and how quarantine, ironically, could make us susceptible to other maladies, due to a lack of microbial exposure. At the psychological level, we describe the ways in which the pandemic can affect mating behavior, cooperation (or the lack thereof), and gender norms, and how we can use disgust to better activate native "behavioral immunity" to combat disease spread. At the cultural level, we describe shifting cultural norms and how we might harness them to better combat disease and the negative social consequences of the pandemic. These insights can be used to craft solutions to problems produced by the pandemic and to lay the groundwork for a scientific agenda to capture and understand what has become, in effect, a worldwide social experiment.

When guiding principles do not guide: The moderating effects of cultural tightness on value-behavior links.

OBJECTIVE: Ample research documented the effects of guiding principles in people's lives, as reflected in personal values, on a variety of behaviors. But do these principles universally guide behaviors across all cultural contexts? To address this question, we investigated the effect of cross-cultural differences in the strength of social norms (i.e., tightness-looseness) on value-behavior relationships. METHOD: Using the archival data from the World Value Survey for 24 nations (N = 38,924; 51.40% female; Mage  = 44.98, SD = 16.87), a multi-level analysis revealed that cultural tightness moderated the effects of individual differences in personal values on behaviors from different life-domains. RESULTS: As hypothesized, the relationships between self-transcendence values with civic involvement and pro-environmental behaviors, and between conservation values with religious behavior were significantly stronger in loose cultures that have weak norms and were almost nonexistent in tight cultures that have strong norms, even when controlling for individualism-collectivism or GDP. CONCLUSIONS: Thus, despite the common belief that people behave in line with their guiding principles, our findings suggest this might not be the case in cultural contexts that put a strong emphasis on norms.

A global analysis of cultural tightness in non-industrial societies.

Human groups have long faced ecological threats such as resource stress and warfare, and must also overcome strains on coordination and cooperation that are imposed by growing social complexity. Tightness-looseness (TL) theory suggests that societies react to these challenges by becoming culturally tighter, with stronger norms and harsher punishment of deviant behaviour. TL theory further predicts that tightening is associated with downstream effects on social, political and religious institutions. Here, we comprehensively test TL theory in a sample of non-industrial societies. Since previous studies of TL theory have sampled contemporary countries and American states, our analysis allows us to examine whether the theory generalizes to societies in the ethnographic record and also to explore new correlates of tightness that vary more in non-industrial societies. We find that tightness covaries across domains of social norms, such as socialization, law and gender. We also show that tightness correlates with several theorized antecedents (ecological threat, complexity, residential homogeneity) and several theorized consequences (intergroup contact, political authoritarianism, moralizing religious beliefs). We integrate these findings into a holistic model of tightness in non-industrial societies and provide metrics that can be used by future studies on cultural tightness in the ethnographic record.

Conflict Changes How People View God.

Religion shapes the nature of intergroup conflict, but conflict may also shape religion. Here, we report four multimethod studies that reveal the impact of conflict on religious belief: The threat of warfare and intergroup tensions increase the psychological need for order and obedience to rules, which leads people to view God as more punitive. Studies 1 (N = 372) and 2 (N = 911) showed that people's concern about conflict correlates with belief in a punitive God. Study 3 (N = 1,065) found that experimentally increasing the salience of conflict increases people's perceptions of the importance of a punitive God, and this effect is mediated by people's support for a tightly regulated society. Study 4 showed that the severity of warfare predicted and preceded worldwide fluctuations in punitive-God belief between 1800 CE and 2000 CE. Our findings illustrate how conflict can change the nature of religious belief and add to a growing literature showing how cultural ecologies shape psychology.

Revenge: A Multilevel Review and Synthesis.

Why do people take revenge? This question can be difficult to answer. Vengeance seems interpersonally destructive and antithetical to many of the most basic human instincts. However, an emerging body of social scientific research has begun to illustrate a logic to revenge, demonstrating why revenge evolved in humans and when and how people take revenge. We review this evidence and suggest that future studies on revenge would benefit from a multilevel perspective in which individual acts of revenge exist within higher-level cultural systems, with the potential to instigate change in these systems over time. With this framework, we can better understand the interplay between revenge's psychological properties and its role in cultural evolution.

Ambivalent stereotypes link to peace, conflict, and inequality across 38 nations.

A cross-national study, 49 samples in 38 nations (n = 4,344), investigates whether national peace and conflict reflect ambivalent warmth and competence stereotypes: High-conflict societies (Pakistan) may need clearcut, unambivalent group images distinguishing friends from foes. Highly peaceful countries (Denmark) also may need less ambivalence because most groups occupy the shared national identity, with only a few outcasts. Finally, nations with intermediate conflict (United States) may need ambivalence to justify more complex intergroup-system stability. Using the Global Peace Index to measure conflict, a curvilinear (quadratic) relationship between ambivalence and conflict highlights how both extremely peaceful and extremely conflictual countries display lower stereotype ambivalence, whereas countries intermediate on peace-conflict present higher ambivalence. These data also replicated a linear inequality-ambivalence relationship.

Conflicting obligations in human social life.

Tomasello describes how the sense of moral obligation emerges from a shared perspective with collaborative partners and in-group members. Our commentary expands this framework to accommodate multiple social identities, where the normative standards associated with diverse group memberships can often conflict with one another. Reconciling these conflicting obligations is argued to be a central part of human morality.

A Tight Spot: How Personality Moderates the Impact of Social Norms on Sojourner Adaptation.

How do you navigate the norms of your new culture when living abroad? Taking an interactionist perspective, we examined how contextual factors and personality traits jointly affect sojourners' adaptation to the host-country culture. We hypothesized that tightness (strong, rigidly imposed norms) of the host culture would be associated with lower levels of adaptation and that tightness of the home culture would be associated with higher levels of adaptation. Further, we proposed that the impact of tightness should be dependent on personality traits associated with navigating social norms (agreeableness, conscientiousness, and honesty-humility). We analyzed longitudinal data from intercultural exchange students ( N = 889) traveling from and to 23 different countries. Multilevel modeling showed that sojourners living in a tighter culture had poorer adaptation than those in a looser culture. In contrast, sojourners originating from a tighter culture showed better adaptation. The negative effect of cultural tightness was moderated by agreeableness and honesty-humility but not conscientiousness.

How culture gets embrained: Cultural differences in event-related potentials of social norm violations.

Humans are unique among all species in their ability to develop and enforce social norms, but there is wide variation in the strength of social norms across human societies. Despite this fundamental aspect of human nature, there has been surprisingly little research on how social norm violations are detected at the neurobiological level. Building on the emerging field of cultural neuroscience, we combine noninvasive electroencephalography (EEG) with a new social norm violation paradigm to examine the neural mechanisms underlying the detection of norm violations and how they vary across cultures. EEG recordings from Chinese and US participants (n = 50) showed consistent negative deflection of event-related potential around 400 ms (N400) over the central and parietal regions that served as a culture-general neural marker of detecting norm violations. The N400 at the frontal and temporal regions, however, was only observed among Chinese but not US participants, illustrating culture-specific neural substrates of the detection of norm violations. Further, the frontal N400 predicted a variety of behavioral and attitudinal measurements related to the strength of social norms that have been found at the national and state levels, including higher culture superiority and self-control but lower creativity. There were no cultural differences in the N400 induced by semantic violation, suggesting a unique cultural influence on social norm violation detection. In all, these findings provided the first evidence, to our knowledge, for the neurobiological foundations of social norm violation detection and its variation across cultures.

The role of entitativity in perpetuating cycles of violence.

Whitehouse's theory on fusion can explain why suicide terrorists are willing to make the ultimate sacrifice for their groups, but the following questions on violent extremism remain: (a) Why are victims of suicide terrorism often innocent bystanders? (b) Why do terrorists seem motivated by ancient conflicts? We incorporate findings from the entitativity literature to provide insights into how perceptions of in-groups and out-groups are key processes influencing violent extremism.

Tightness-looseness across the 50 united states.

This research demonstrates wide variation in tightness-looseness (the strength of punishment and degree of latitude/permissiveness) at the state level in the United States, as well as its association with a variety of ecological and historical factors, psychological characteristics, and state-level outcomes. Consistent with theory and past research, ecological and man-made threats--such as a higher incidence of natural disasters, greater disease prevalence, fewer natural resources, and greater degree of external threat--predicted increased tightness at the state level. Tightness is also associated with higher trait conscientiousness and lower trait openness, as well as a wide array of outcomes at the state level. Compared with loose states, tight states have higher levels of social stability, including lowered drug and alcohol use, lower rates of homelessness, and lower social disorganization. However, tight states also have higher incarceration rates, greater discrimination and inequality, lower creativity, and lower happiness relative to loose states. In all, tightness-looseness provides a parsimonious explanation of the wide variation we see across the 50 states of the United States of America.

The Evolutionary Basis of Honor Cultures.

Around the globe, people fight for their honor, even if it means sacrificing their lives. This is puzzling from an evolutionary perspective, and little is known about the conditions under which honor cultures evolve. We implemented an agent-based model of honor, and our simulations showed that the reliability of institutions and toughness of the environment are crucial conditions for the evolution of honor cultures. Honor cultures survive when the effectiveness of the authorities is low, even in very tough environments. Moreover, the results show that honor cultures and aggressive cultures are mutually dependent in what resembles a predator-prey relationship described in the renowned Lotka-Volterra model. Both cultures are eliminated when institutions are reliable. These results have implications for understanding conflict throughout the world, where Western-based strategies are exported, often unsuccessfully, to contexts of weak institutional authority wherein honor-based strategies have been critical for survival.