Evidence of partner choice heuristics in a one-shot bargaining game

Exploring Within-Gender Differences in Friendships Using an Online Social Network

People tend to befriend others similar to themselves, generating a pattern called homophily. However, existing studies on friendship patterns often rely on surveys that assess the perspective of relatively few participants on their friendships but do not measure actualized friendship patterns. Here, we used data from a large Slovakian online social network to assess the role of gender, age, and body mass index (BMI) in same-gender online connections among more than 400,000 users. We found that age and BMI homophily occurred in both men's and women's same-gender connections, but somewhat more strongly among men's. Yet, as women diverged in BMI, their connections were less likely to be reciprocated. We discuss how the evolutionary legacy of men's coalitional competition (e.g., warfare) and women's mating competition or recruitment of allocare providers might contribute to these patterns in modern same-gender relationships. For example, men's engagement in physical activities may lead to similar formidability levels among their same-gender peers. Altogether, our findings highlight the importance of trait similarity to same-gender friendship patterns.

Willingness valued more than ability in partner choice: Insights into behavioral and ERP data

In human cooperation, people prefer to choose partners with high willingness and ability-while both are valued by partners, individuals often prioritize willingness. Two event-related potential (ERP) experiments were conducted to discern the neural processes underpinning this preference. In the first experiment, participants made a choice between two potential partners and received feedback on the selected partner's willingness to cooperate. This was followed by feedback on the partner's task performance (ability) or a gambling outcome. In contrast, the second experiment first provided feedback on ability, then presented feedback on willingness or a gambling outcome. This study revealed that a potential partner's willingness trait significantly influences individuals' emotional evaluations and monetary allocations than the ability trait. Electrophysiological data indicated that low-willingness feedback elicited a diminished feedback-related negative (FRN) and an amplified P3 compared to high-willingness feedback. In contrast, no such difference was discernible between high- and low-ability feedback. Moreover, the P3 difference from high versus low willingness was considerably more pronounced than that from gambling outcomes, whereas the difference wave between high and low ability paralleled gambling outcomes. These findings bolster the novel finding that partner willingness may provide more substantial social rewards than ability. Furthermore, this study provides the first ERP evidence of willingness and ability trait perceptions in partner choice decisions.

Enhancing musical pleasure through shared musical experience

Music and social interactions represent two of the most important sources of pleasure in our lives, both engaging the mesolimbic dopaminergic system. However, there is limited understanding regarding whether and how sharing a musical activity in a social context influences and modifies individuals' rewarding experiences. Here, we aimed at (1) modulating the pleasure derived from music under different social scenarios and (2) further investigating its impact on reward-related prosocial behavior and memory. Across three online experiments, we simulated a socially shared music listening and found that participants' music reward was significantly modulated by the social context, with higher reported pleasure for greater levels of social sharing. Furthermore, the increased pleasure reported by the participants positively influenced prosocial behavior and memory outcomes, highlighting the facilitating role of socially boosted reward. These findings provide evidence about the rewarding nature of socially driven music experiences, with important potential implications in educational and clinical settings.

Younger adults are more prosocial than older adults in economic decision making results from the give and take game

The present study was designed to investigate the disadvantageous and advantageous inequity aversion of young and older adults in situations which allowed them to maximize or minimize payoff inequalities. Given the very limited evidence regarding an actual age-related effect on inequity aversion, the purpose of this study was to examine this question using an economic game, "the Give-and-Take Game", which is able to circumvent certain limitations of the Ultimatum Game, to evaluate inequity aversion (i.e., a same behaviour which can be induced by opposite motivations: prosocial vs. pro-self vs. altruistic orientations). In the "Give-and-Take Game", a sum of money was randomly distributed between the participant and a dummy player. These distributions created monetary inequalities, advantageous either for the participant (to examine advantageous inequity aversion) or for the other player (to examine disadvantageous inequity aversion). Different response options were proposed to the participants to either maximize or minimize payoff inequalities between the players. This procedure not only allowed to differentiate individual's profiles with more prosocial vs. pro-self vs. altruistic orientations, but also to examine age-related effects on these profiles. The results showed that older adults showed a more important pro-self orientation compared to their younger counterparts. They more frequently selected the options which maximized their own payoffs and were less averse to advantageous inequity compared to young adults. In contrast, young adults showed a similar level of advantageous and disadvantageous inequity aversion. Older adults focused on the economic and competitive dimension of the game, which may have motivated them to maximize their own payoffs. Conversely, young adults took into account the social dimension of the game, focusing on a fair monetary distribution.

Attractiveness Differentially Affects Direct Versus Indirect Face Evaluations in Two Cultures

Although decades of research have identified facial features relating to people's evaluations of faces, specific features have largely been examined in isolation from each other. Recent work shows that considering the relative importance of these features in face evaluations is important to test theoretical assumptions of impression formation. Here, we examined how two facial features of evolutionary interest, facial attractiveness and facial-width-to-height ratio (FWHR), relate to evaluations of faces across two cultures. Because face evaluations are typically directly measured via self-reports, we also examined whether these features exert differential effects on both direct and indirect face evaluations. Evaluations of standardized photos naturally varying in facial attractiveness and FWHR were collected using the Affect Misattribution Procedure in the United States and Turkey. When their relative contributions were considered in the same model, facial attractiveness, but not FWHR, related to face evaluations across cultures. This positive attractiveness effect was stronger for direct versus indirect evaluations across cultures. These findings highlight the importance of considering the relative contributions of facial features to evaluations across cultures and suggest a culturally invariant role of attractiveness when intentionally evaluating faces.

The Shame System Operates With High Precision

Previous research indicates that the anticipatory shame an individual feels at the prospect of taking a disgraceful action closely tracks the degree to which local audiences, and even foreign audiences, devalue those individuals who take that action. This supports the proposition that the shame system (a) defends the individual against the threat of being devalued, and (b) balances the competing demands of operating effectively yet efficiently. The stimuli events used in previous research were highly variable in their perceived disgracefulness, ranging in rated shame and audience devaluation from low (e.g., missing the target in a throwing game) to high (e.g., being discovered cheating on one's spouse). But how precise is the tracking of audience devaluation by the shame system? Would shame track devaluation for events that are similarly low (or high) in disgracefulness? To answer this question, we conducted a study with participants from the United States and India. Participants were assigned, between-subjects, to one of two conditions: shame or audience devaluation. Within-subjects, participants rated three low-variation sets of 25 scenarios each, adapted from Mu, Kitayama, Han, & Gelfand (2015), which convey (a) appropriateness (e.g., yelling at a rock concert), (b) mild disgracefulness (e.g., yelling on the metro), and (c) disgracefulness (e.g., yelling in the library), all presented un-blocked, in random order. Consistent with previous research, shame tracked audience devaluation across the high-variation superset of 75 scenarios, both within and between cultures. Critically, shame tracked devaluation also within each of the three sets. The shame system operates with high precision.

A kin-selection model of fairness in heterogeneous populations

Humans and other primates exhibit pro-social preferences for fairness. These preferences are thought to be reinforced by strong reciprocity, a policy that rewards fair actors and punishes unfair ones. Theories of fairness based on strong reciprocity have been criticized for overlooking the importance of individual differences in socially heterogeneous populations. Here, we explore the evolution of fairness in a heterogeneous population. We analyse the Ultimatum Game in cases where players' roles in the game are determined by their status. Importantly, our model allows for non-random pairing of players, and so we also explore the role played by kin selection in shaping fairness. Our kin-selection model shows that, when individuals condition their behaviour on their role in the game, fairness can be understood as either altruistic or spiteful. Altruistic fairness directs resources from less valuable members of a genetic lineage to more valuable members of the same lineage, whereas spiteful fairness keeps resources away from the competitors of the actor's high-value relatives. When individuals express fairness unconditionally it can be understood as altruistic or selfish. When it is altruistic, unconditional fairness again serves to direct resources to high-value members of genetic lineages. When it is selfish, unconditional fairness simply improves an individual's own standing. Overall, we expand kin-selection based explanations for fairness to include motivations other than spite. We show, therefore, that one need not invoke strong reciprocity to explain the advantage of fairness in heterogeneous populations.

The evolution of shame and its display

The shame system appears to be natural selection's solution to the adaptive problem of information-triggered reputational damage. Over evolutionary time, this problem would have led to a coordinated set of adaptations - the shame system - designed to minimise the spread of negative information about the self and the likelihood and costs of being socially devalued by others. This information threat theory of shame can account for much of what we know about shame and generate precise predictions. Here, we analyse the behavioural configuration that people adopt stereotypically when ashamed - slumped posture, downward head tilt, gaze avoidance, inhibition of speech - in light of shame's hypothesised function. This behavioural configuration may have differentially favoured its own replication by (a) hampering the transfer of information (e.g. diminishing audiences' tendency to attend to or encode identifying information - shame camouflage) and/or (b) evoking less severe devaluative responses from audiences (shame display). The shame display hypothesis has received considerable attention and empirical support, whereas the shame camouflage hypothesis has to our knowledge not been advanced or tested. We elaborate on this hypothesis and suggest directions for future research on the shame pose.

Our Grandmothers' Legacy: Challenges Faced by Female Ancestors Leave Traces in Modern Women's Same-Sex Relationships

Investigations of women's same-sex relationships present a paradoxical pattern, with women generally disliking competition, yet also exhibiting signs of intrasexual rivalry. The current article leverages the historical challenges faced by female ancestors to understand modern women's same-sex relationships. Across history, women were largely denied independent access to resources, often depending on male partners' provisioning to support themselves and their children. Same-sex peers thus became women's primary romantic rivals in competing to attract and retain relationships with the limited partners able and willing to invest. Modern women show signs of this competition, disliking and aggressing against those who threaten their romantic prospects, targeting especially physically attractive and sexually uninhibited peers. However, women also rely on one another for aid, information, and support. As most social groups were patrilocal across history, upon marriage, women left their families to reside with their husbands. Female ancestors likely used reciprocal altruism or mutualism to facilitate cooperative relationships with nearby unrelated women. To sustain these mutually beneficial cooperative exchange relationships, women may avoid competitive and status-striving peers, instead preferring kind, humble, and loyal allies. Ancestral women who managed to simultaneously compete for romantic partners while forming cooperative female friendships would have been especially successful. Women may therefore have developed strategies to achieve both competitive and cooperative goals, such as guising their intrasexual competition as prosociality or vulnerability. These historical challenges make sense of the seemingly paradoxical pattern of female aversion to competition, relational aggression, and valuation of loyal friends, offering insight into possible opportunities for intervention.

Hadza hunter-gatherers with greater exposure to other cultures share more with generous campmates

Humans are motivated to compete for access to valuable social partners, which is a function of their willingness to share and ability to generate resources. However, relative preferences for each trait should be responsive to socioecological conditions. Here, we test the flexibility of partner choice psychology among Hadza hunter-gatherers of Tanzania. Ninety-two Hadza ranked their campmates on generosity and foraging ability and then shared resources with those campmates. We found Hadza with greater exposure to other cultures shared more with campmates ranked higher on generosity, whereas Hadza with lower exposure showed a smaller preference for sharing with generous campmates. This moderating effect was specific to generosity-regardless of exposure, Hadza showed only a small preference for sharing with better foragers. We argue this difference in preferences is due to high exposure Hadza having more experience cooperating with others in the absence of strong norms of sharing, and thus are exposed to greater variance in willingness to cooperate among potential partners increasing the benefits of choosing partners based on generosity. As such, participants place a greater emphasis on choosing more generous partners, highlighting the flexibility of partner preferences.

Why Warmth Matters More Than Competence: A New Evolutionary Approach

Multiple lines of evidence suggest that there are two major dimensions of social perception, often called warmth and competence, and that warmth is prioritized over competence in multiple types of social decision-making. Existing explanations for this prioritization argue that warmth is more consequential for an observer's welfare than is competence. We present a new explanation for the prioritization of warmth based on humans' evolutionary history of cooperative partner choice. We argue that the prioritization of warmth evolved because ancestral humans faced greater variance in the warmth of potential cooperative partners than in their competence but greater variance in competence over time within cooperative relationships. These each made warmth more predictive than competence of the future benefits of a relationship, but because of differences in the distributions of these traits, not because of differences in their intrinsic consequentiality. A broad, synthetic review of the anthropological literature suggests that these conditions were characteristic of the ecologies in which human social cognition evolved, and agent-based models demonstrate the plausibility of these selection pressures. We conclude with future directions for the study of preferences and the further integration of social and evolutionary psychology.

Motivations to reciprocate cooperation and punish defection are calibrated by estimates of how easily others can switch partners

Evolutionary models of dyadic cooperation demonstrate that selection favors different strategies for reciprocity depending on opportunities to choose alternative partners. We propose that selection has favored mechanisms that estimate the extent to which others can switch partners and calibrate motivations to reciprocate and punish accordingly. These estimates should reflect default assumptions about relational mobility: the probability that individuals in one’s social world will have the opportunity to form relationships with new partners. This prior probability can be updated by cues present in the immediate situation one is facing. The resulting estimate of a partner’s outside options should serve as input to motivational systems regulating reciprocity: Higher estimates should down-regulate the use of sanctions to prevent defection by a current partner, and up-regulate efforts to attract better cooperative partners by curating one’s own reputation and monitoring that of others. We tested this hypothesis using a Trust Game with Punishment (TGP), which provides continuous measures of reciprocity, defection, and punishment in response to defection. We measured each participant’s perception of relational mobility in their real-world social ecology and experimentally varied a cue to partner switching. Moreover, the study was conducted in the US (n = 519) and Japan (n = 520): societies that are high versus low in relational mobility. Across conditions and societies, higher perceptions of relational mobility were associated with increased reciprocity and decreased punishment: i.e., those who thought that others have many opportunities to find new partners reciprocated more and punished less. The situational cue to partner switching was detected, but relational mobility in one’s real social world regulated motivations to reciprocate and punish, even in the experimental setting. The current research provides evidence that motivational systems are designed to estimate varying degrees of partner choice in one’s social ecology and regulate reciprocal behaviors accordingly.

Third-Party Perceptions of Male and Female Status: Male Physical Strength and Female Physical Attractiveness Cue High Status

Status is a universal feature of human sociality. A lesser-studied adaptive problem surrounding status is assessing who has which levels of status in a given group (e.g., identifying which people possess high status). Here, we integrate theory and methods from evolutionary social science, animal behavior, and social psychology, and we use an emotion inference paradigm to investigate what cues render people high status in the eyes of social perceivers. This paradigm relies on robust associations between status and emotion display—particularly the anger display. If a target is expected to enact (but not necessarily feel) anger, this would suggest that social perceivers view that target as higher status. By varying target attributes, we test whether those attributes are considered status cues in the eyes of social perceivers. In two well-powered, pre-registered experiments in the United States (N = 451) and India (N = 378), participants read one of eight vignettes about a male or female target—described as high or low in either physical strength or physical attractiveness (possible status cues)—who is thwarted by another person, and then reported expectations of the target’s felt and enacted anger. We find that people expected physically stronger (versus less strong) men and more (versus less) physically attractive women to enact greater anger when thwarted by a same-sex other. Strength had no significant effect on estimations of female status and attractiveness had no significant effect on estimations of male status. There were no differences in expectations of felt anger. Results suggest that people use men’s strength and women’s attractiveness as status cues. Moreover, results underscore the notion that focusing on male-typical cues of status might obscure our understanding of the female status landscape. We discuss how this paradigm might be fruitfully employed to examine and discover other unexplored cues of male and female status.

Social motivation is associated with increased weight granted to cooperation-related impressions in face evaluation tasks

It is a trope in psychological science to define the human species as inherently social. Yet, despite its key role in human behaviour, the mechanisms by which social bonding actually shapes social behaviour have not been fully characterized. Across six studies, we show that the motivation for social bonding does not indiscriminately increase individuals’ willingness to approach others but that it is instead associated with specific variations in social evaluations. Studies 1–4 demonstrate that social motivation is associated with a larger importance granted to cooperation-related impressions, i.e. perceived trustworthiness, during social evaluations. Studies 5 and 6 further reveal that this weighting difference leads strongly socially motivated participants to approach more partners that are perceived as both dominant and trustworthy. Taken together, our results provide support for the idea that humans’ social motivation is associated with specific social preferences that could favour successful cooperative interactions and a widening of people’s cooperative circle.

Pleasant body odours, but not genetic similarity, influence trustworthiness in a modified trust game

Identifying trustworthy partners is an important adaptive challenge for establishing mutually cooperative relationships. Previous studies have demonstrated a marked relationship between a person's attractiveness and his apparent trustworthiness (beauty premium). Kin selection theory, however, suggests that cues to kinship enhance trustworthiness. Here we directly tested predictions of the beauty premium and kin selection theory by using body odours as cues to trustworthiness. Body odours reportedly portray information about an individuals' genotype at the human leucocyte antigen system (HLA) and thus olfactory cues in body odours serve as a promising means for kin recognition. Ninety men played trust games in which they divided uneven sums of monetary units between two male trustees represented by their body odour and rated each body odour for pleasantness. Half of the odours came from HLA-similar men (suggesting closer kin) and half from HLA dissimilar men (suggesting non-kin). We found that the amount of money the players transferred was not related to HLA-similarity, but to the pleasantness of the trustee's body odour. By showing that people with more pleasant body odours are trusted more than people with unpleasant body odour we provide evidence for a "beauty-premium" that overrides any putative effect of kin.

Wealth-relative effects in cooperation games

This paper investigates cooperation games in which poor agents do not benefit from cooperation with wealthy agents. They instead benefit from considering wealth relative to decision payoffs of fitness or wealth. Of concern is the effect of cooperation on participants, their rational self-interest and choices, and not the evolution of cooperation directly. The accumulation of fitness or wealth has been shown in the literature to lead to different optimal strategies for wealthy and poor players in Chicken games. The effect could have important explanatory power if it were more broadly applicable. First we empirically compare two published results, one involving the temptation parameter vs. degree of cooperation in Prisoner's Dilemma, and the other a surprising result from a public goods game with participants from different cultures, networks and wealth in which a fixed rather than relative payoff scheme was used. Using the temptation data to calibrate the public goods behavior suggests wealth factors can provide an explanation for the results. Second we show using simulation that adding a survival threshold to a wealth or fitness accumulating Iterated Prisoner's Dilemma produces a wealth relative effect. We clarify previous results to show the poor must avoid survival risk, regardless of whether this is associated with cooperation or defection. We do this by introducing the Farmer's Game, a simulation of Iterated Prisoner's Dilemma with wealth accumulation and a survival threshold. This is used to evaluate the Tit-for-Tat strategy and four variants. Equilibrium payoffs keep the game scaled to social relevance, with a fraction of all payoffs externalized as a turn cost parameter. Findings include poor performance of Tit-for-Tat near the survival threshold, superior performance of low risk strategies for both poor and wealthy players, dependence of survival of the poor near the threshold on Tit-for-Tat forgiveness, unexpected optimization of forgiveness without encountering a social dilemma, improved performance of a diverse mix of strategies, and a more abrupt threshold of social catastrophe for the better performing mix. Lastly we compare cooperating and non-cooperating societies using the simulation and discover disturbing connections between cooperation and familiar non-egalitarian wealth distribution patterns.

Hadza Hunter-Gatherers Disagree on Perceptions of Moral Character

To the extent that moral character is grounded in stable and observable truths, there should exist agreement between people in their judgments of others’ character. In Western populations, this agreement is found. We examine whether this is universal in Hadza hunter-gatherers of Tanzania. Ninety-four judges ranked their campmates on global character and relevant character traits for a total of 802 observations. Judges disagreed on rankings of global character, generosity, and honesty but agreed more on hard work and hunting ability. Individual rankings on specific traits predicted character evaluations. There was agreement between judges on the extent to which generosity and hard work related to character. These findings suggest that Hadza have shared beliefs about what traits constitute character but disagree on which of their campmates exhibit these traits. We discuss these findings in light of other research suggesting that stable moral dispositions may not be universal.

It is not all about mating: Attractiveness predicts partner value across multiple relationship domains

An account of the "beauty premium" based only on mating motivations overlooks adaptationist models of social valuation that have broader explanatory power. We suggest a broader approach based on evolved preferences for attractive partners in multiple cooperative domains (not just mating), which accounts for many observations of attractiveness-based preferential treatment more comfortably than does the target article's mating-specific account.

Can I Rely on You?

This paper introduces a strategic element into the dictator game by allowing recipients to select their dictator. Recipients are presented with the photographs of two dictators and the envelopes containing their allocations, and are then asked to select which dictator’s gift they would like to receive. The recipient is paid the contents of the envelope they select. The photographs carry information about the gender and race/ethnicity of the dictators, and we ask an independent sample of raters to evaluate the photographs for other characteristics. While gender and ethnicity do not affect the recipient’s choice, one characteristic inferred from the photos makes them significantly more likely to be selected: Their perceived reliability.

Cues of upper body strength account for most of the variance in men's bodily attractiveness

Evolution equips sexually reproducing species with mate choice mechanisms that function to evaluate the reproductive consequences of mating with different individuals. Indeed, evolutionary psychologists have shown that women's mate choice mechanisms track many cues of men's genetic quality and ability to invest resources in the woman and her offspring. One variable that predicted both a man's genetic quality and his ability to invest is the man's formidability (i.e. fighting ability or resource holding power/potential). Modern women, therefore, should have mate choice mechanisms that respond to ancestral cues of a man's fighting ability. One crucial component of a man's ability to fight is his upper body strength. Here, we test how important physical strength is to men's bodily attractiveness. Three sets of photographs of men's bodies were shown to raters who estimated either their physical strength or their attractiveness. Estimates of physical strength determined over 70% of men's bodily attractiveness. Additional analyses showed that tallness and leanness were also favoured, and, along with estimates of physical strength, accounted for 80% of men's bodily attractiveness. Contrary to popular theories of men's physical attractiveness, there was no evidence of a nonlinear effect; the strongest men were the most attractive in all samples.

Folk-economic beliefs: An evolutionary cognitive model

The domain of "folk-economics" consists in explicit beliefs about the economy held by laypeople, untrained in economics, about such topics as, for example, the causes of the wealth of nations, the benefits or drawbacks of markets and international trade, the effects of regulation, the origins of inequality, the connection between work and wages, the economic consequences of immigration, or the possible causes of unemployment. These beliefs are crucial in forming people's political beliefs and in shaping their reception of different policies. Yet, they often conflict with elementary principles of economic theory and are often described as the consequences of ignorance, irrationality, or specific biases. As we will argue, these past perspectives fail to predict the particular contents of popular folk-economic beliefs and, as a result, there is no systematic study of the cognitive factors involved in their emergence and cultural success. Here we propose that the cultural success of particular beliefs about the economy is predictable if we consider the influence of specialized, largely automatic inference systems that evolved as adaptations to ancestral human small-scale sociality. These systems, for which there is independent evidence, include free-rider detection, fairness-based partner choice, ownership intuitions, coalitional psychology, and more. Information about modern mass-market conditions activates these specific inference systems, resulting in particular intuitions, for example, that impersonal transactions are dangerous or that international trade is a zero-sum game. These intuitions in turn make specific policy proposals more likely than others to become intuitively compelling, and, as a consequence, exert a crucial influence on political choices.

Cross-cultural regularities in the cognitive architecture of pride

Pride occurs in every known culture, appears early in development, is reliably triggered by achievements and formidability, and causes a characteristic display that is recognized everywhere. Here, we evaluate the theory that pride evolved to guide decisions relevant to pursuing actions that enhance valuation and respect for a person in the minds of others. By hypothesis, pride is a neurocomputational program tailored by selection to orchestrate cognition and behavior in the service of: (i) motivating the cost-effective pursuit of courses of action that would increase others' valuations and respect of the individual, (ii) motivating the advertisement of acts or characteristics whose recognition by others would lead them to enhance their evaluations of the individual, and (iii) mobilizing the individual to take advantage of the resulting enhanced social landscape. To modulate how much to invest in actions that might lead to enhanced evaluations by others, the pride system must forecast the magnitude of the evaluations the action would evoke in the audience and calibrate its activation proportionally. We tested this prediction in 16 countries across 4 continents (n = 2,085), for 25 acts and traits. As predicted, the pride intensity for a given act or trait closely tracks the valuations of audiences, local (mean r = +0.82) and foreign (mean r = +0.75). This relationship is specific to pride and does not generalize to other positive emotions that coactivate with pride but lack its audience-recalibrating function.