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Conformity refers to phenomena where people match their behavior to others. Much research has focused on cases where people observe others in identical situations, saying little about its depth or generalizability. When conforming, do people revise behaviors only in that specific situation, or do they update more deeply to maintain consistent behaviors across situations? Using simulations, we first show that deep and shallow conformity leads to contrasting group dynamics; only with deep conformity can groups accumulate improvements beyond individual lifespans. We further conduct an experiment using an estimation task to examine the depths of conformity in humans. People generally extended conformist social influence to new situations without direct reference to others. However, those who simply averaged their answer with that of the direct reference showed notable failures in this generalization. Collectively, our research highlights the importance of distinguishing different depths of conformity when studying social influence and resulting group outcomes.

People vary both in their embrace of their society's traditions, and in their perception of hazards as salient and necessitating a response. Over evolutionary time, traditions have offered avenues for addressing hazards, plausibly resulting in linkages between orientations toward tradition and orientations toward danger. Emerging research documents connections between traditionalism and threat responsivity, including pathogen-avoidance motivations. Additionally, because hazard-mitigating behaviors can conflict with competing priorities, associations between traditionalism and pathogen avoidance may hinge on contextually contingent tradeoffs. The COVID-19 pandemic provides a real-world test of the posited relationship between traditionalism and hazard avoidance. Across 27 societies (N = 7844), we find that, in a majority of countries, individuals' endorsement of tradition positively correlates with their adherence to costly COVID-19-avoidance behaviors; accounting for some of the conflicts that arise between public health precautions and other objectives further strengthens this evidence that traditionalism is associated with greater attention to hazards.

The allocation of scarce resources is a ubiquitous process in human societies, yet it is challenging to aggregate peoplesdiverse distributive viewpoints into group consensus. We investigate whether such heterogeneity in preferences may bereduced when people participate in group discussion in a distribution task. In two interactive experiments, we foundthat after group discussion, participants became less inequity-averse and preferred the maximin allocation. Analyses ofparticipants conversations and information-search behaviors showed that such shifts toward the maximin allocation werefacilitated by a strong concern for the worst-off recipient during group discussion. These results suggest that a maximinconcern exhibited in discussion helped participants to understand the difference between the inequity-aversion principleand the maximin principle, which are often confounded in individual judgments. These results provide empirical insightinto how social interaction can help to aggregate peoples diverse distributive preference into a social consensus.

Laughter is a nonverbal vocalization occurring in every known culture, ubiquitous across all forms of human social interaction. Here, we examined whether listeners around the world, irrespective of their own native language and culture, can distinguish between spontaneous laughter and volitional laughter-laugh types likely generated by different vocal-production systems. Using a set of 36 recorded laughs produced by female English speakers in tests involving 884 participants from 21 societies across six regions of the world, we asked listeners to determine whether each laugh was real or fake, and listeners differentiated between the two laugh types with an accuracy of 56% to 69%. Acoustic analysis revealed that sound features associated with arousal in vocal production predicted listeners' judgments fairly uniformly across societies. These results demonstrate high consistency across cultures in laughter judgments, underscoring the potential importance of nonverbal vocal communicative phenomena in human affiliation and cooperation.

Recent research using attention-monitoring techniques and fMRI has revealed that a shared neurocognitive mechanismunderlies both social decision making concerning the welfare of others and purely economic decision making for oneself.Such commonalities have been demonstrated mainly in isolated contexts, and it remains to be seen whether they extendto settings involving interactions with fellow decision makers. Using a behavioral study of distributive choices for othersand gambling decisions for self, we investigated how self-censorship in social contexts may mitigate the cognitive com-monalities demonstrated in isolated contexts. Results showed that, in both tasks, individual participants took more timeto respond when they expected subsequent discussion with another participant about reaching a consensus. In addition,we found a cognitive pattern unique to distributive choices for others only: participants expecting social interaction madetheir distributive choices in a more cognitively consistent manner, aligning with a rationale that they thought would bedefensible in subsequent discussion. No such systematic pattern was observed in gambling choices for self. These resultsindicate that anticipation of subsequent social interaction triggers self-censoring processes for some (but not all) tasks,whereby participants pre-edit their individual decisions systematically to prepare for social interaction.

The automatic contagion of emotion is considered crucial in interpersonal communication. In face-to-face interac-tions, people could be both the receiver and sender of emotional content. Thus, contagion may have bidirectional influenceson the emotional states of individuals. However, many studies have mainly dealt with unidirectional contagion, such that theexpression of pain in a target entails a reaction of pain in the observer. In this study, we demonstrated bidirectional emotionalcontagion in the experience of thermal pain during interaction. Firstly, we showed that the physiological responses of dyadmembers were correlated with each other when they could interact compared to when they were impaired to see each other.Further, we demonstrated that individuals showed higher or lower physiological responses when their partners experiencedstronger or weaker stimuli respectively. Thus, people can develop similar physiological responses through interactions, and thiseffect seems to induce a change in the responsivity to stimuli.

Laughter is a nonverbal vocal expression that often communicates positive affect and cooperative intent in humans. Temporally coincident laughter occurring within groups is a potentially rich cue of affiliation to overhearers. We examined listeners' judgments of affiliation based on brief, decontextualized instances of colaughter between either established friends or recently acquainted strangers. In a sample of 966 participants from 24 societies, people reliably distinguished friends from strangers with an accuracy of 53-67%. Acoustic analyses of the individual laughter segments revealed that, across cultures, listeners' judgments were consistently predicted by voicing dynamics, suggesting perceptual sensitivity to emotionally triggered spontaneous production. Colaughter affords rapid and accurate appraisals of affiliation that transcend cultural and linguistic boundaries, and may constitute a universal means of signaling cooperative relationships.

We introduce a game theory model of individual decisions to cooperate by contributing personal resources to group decisions versus by free riding on the contributions of other members. In contrast to most public-goods games that assume group returns are linear in individual contributions, the present model assumes decreasing marginal group production as a function of aggregate individual contributions. This diminishing marginal returns assumption is more realistic and generates starkly different predictions compared to the linear model. One important implication is that, under most conditions, there exist equilibria where some, but not all, members of a group contribute, even with completely self-interested motives. An agent-based simulation confirmed the individual and group advantages of the equilibria in which behavioral asymmetry emerges from a game structure that is a priori perfectly symmetric for all agents (all agents have the same payoff function and action space but take different actions in equilibria). A behavioral experiment demonstrated that cooperators and free riders coexist in a stable manner in groups performing with the nonlinear production function. A collateral result demonstrated that, compared to a dictatorial decision scheme guided by the best member in a group, the majority/plurality decision rules can pool information effectively and produce greater individual net welfare at equilibrium, even if free riding is not sanctioned. This is an original proof that cooperation in ad hoc decision-making groups can be understood in terms of self-interested motivations and that, despite the free-rider problem, majority/plurality decision rules can function robustly as simple, efficient social decision heuristics. (Contains 15 figures, 1 table and 9 footnotes.)

How should groups make decisions? The authors provide an original evaluation of 9 group decision rules based on their adaptive success in a simulated test bed environment. When the adaptive success standard is applied, the majority and plurality rules fare quite well, performing at levels comparable to much more resource-demanding rules such as an individual judgment averaging rule. The plurality rule matches the computationally demanding Condorcet majority winner that is standard in evaluations of preferential choice. The authors also test the results from their theoretical analysis in a behavioral study of nominal human group decisions, and the essential findings are confirmed empirically. The conclusions of the present analysis support the popularity of majority and plurality rules in truth-seeking group decisions.