Maintaining multiple intimate relationships entails some risks and complications beyond exclusive pair bonding (i.e., monogamy). Consensual non-monogamy (CNM; e.g., polyamory, swinging, or open relationships) allegedly reduces these risks and complications, but no one has tried to comprehensively document typical CNM risk management practices, nor analyzed the relationship outcomes of those who use these practices. We developed the Multiple Relationships Maintenance Scale (MRMS) to examine how engagement in common CNM practices predicts relationship quality among people with one or more partners. In Study 1, a community sample of people with CNM experience (N = 429) nominated the best practices for maintaining CNM. Responses were combined with theory-derived practices to create the MRMS. In Study 2, we administered the MRMS in three international online surveys (N = 4,290) to assess factor structure and construct validity. Factor analysis revealed nine practices: disclosure of one’s extra-pair attractions to a partner, open communication about jealousy, compersion, willingness to care for unrelated children, shared extra-pair sexual experiences, partner (non)hierarchy, sexual health maintenance, thoughtful resource distribution among partners, and reputation management. Data from one of the three surveys (n = 871) showed that each practice had distinctive patterns of association with previous CNM experience, relationship and sexual satisfaction, partner investment and interdependence, and self-reported infidelity (i.e., how often extra-pair interactions feel to violate an existing relationship’s agreements). We discuss how the MRMS may be used to study how people in CNM relationships maintain multiple intimate relationships.

This research examines the evolutionary and social functions of gaming by proposing that rule-bounded competitive play could operate as a strategy for forming and sustaining long-term alliances. To investigate this hypothesis, we conducted two complementary studies. Study 1 tested whether engaging in a game, compared with a non-game interaction (role playing), influences how same-sex strangers perceive each other's value and relational closeness across repeated encounters. Although both constructs changed over time, gaming did not produce stronger or faster shifts than the comparison activity. Study 2 used an agent-based evolutionary model to explore the conditions under which gaming could spread in a population as a tactic for ally selection. The simulations indicated that gaming is favored when players possess above-average skill and when environmental risk coevolves with population skill; otherwise, gaming tends to drift or disappear. Together, these studies suggest that the social effects of gaming are context-dependent and may not emerge uniformly across game types or interaction settings. The modeling results highlight that risk, skill, and reliability of performance cues are key parameters for understanding the potential evolutionary role of gaming in alliance formation. Future work should integrate long-term interactions, participants' skill levels, and different game ecologies to clarify under what circumstances gaming strengthens social bonds.

According to the attractiveness halo effect, global person perceptions are biased by physical attractiveness: More attractive people are ascribed positive attributes like competence, prosociality, and health, with cross-cultural variation in such perceptions. However, extant cross-cultural studies mostly considered cross-cultural differences only in either observers or targets. This preregistered study explored cross-cultural nuances in the attractiveness halo effect for Brazilian and German target men and women, as perceived by Brazilian and German observers. Facial photos of 583 targets were judged separately for attractiveness, prosociality, health, intelligence, social competence, familiarity, and physical and social dominance by 554 Brazilian and 326 German observers. Ratings between Brazilian and German observers for the same target group and attribute were strongly positively correlated, except for familiarity for German male targets. Attractiveness halo effects were overall strong (stronger for health, social competence, and familiarity compared to social dominance, prosociality, and intelligence) and mostly consistent for Brazilian and German targets and observers, with few exceptions. Only for physical dominance, associations were mixed by target gender and nationality. This study supports a putative universality of attractiveness halo effects and also contributes to a deeper understanding of subtle variations in the halo effects of men’s and women’s attractiveness in more individualistic versus more collectivistic cultures.

According to the attractiveness halo effect, global person perceptions are biased by physical attractiveness. Few studies have shown similar influences by unattractiveness, with unattractive people being ascribed negative attributes. This preregistered study compared the strength of (positive) attractiveness halo effects with negative halo effects employing target samples from two phenotypically distinct populations. Facial photos of 154 German and 149 Brazilian women were judged separately for their attractiveness, social (in-)competence, intellectual (in )competence, and emotional (in-)stability by 168 female German raters. Results showed moderate-to-strong positive associations of perceived attractiveness with all three positively framed attributes, and moderate-to-strong negative correlations with all three negatively framed attributes, which did not differ considerably in magnitude, nor between German and Brazilian targets (one exception for intellectual incompetence). In exploratory analyses, judgements of social competence, intellectual competence, and emotional stability were in most cases significantly more negative for low- than for medium-attractiveness targets, than they were positive for high- than for medium-attractiveness targets. These findings provide a systematic comparison of positive and negative halo effects, revealing that negative biases for unattractive individuals can be at least as pronounced as positive biases for attractive individuals. These effects also mostly generalize across German and Brazilian faces, extending evidence on halo effects beyond single‑population samples.

This research examines the evolutionary and social functions of gaming by proposing that rule-bounded competitive play may operate as a strategy for forming and sustaining long-term alliances. To investigate this hypothesis, we conducted two complementary studies. Study 1 tested whether engaging in a game, compared with a non-game interaction, influences how same-sex strangers perceive each other’s value and relational closeness across repeated encounters. Although both constructs changed over time, gaming did not produce stronger or faster shifts than the comparison activity. Study 2 used an agent-based evolutionary model to explore the conditions under which gaming could spread in a population as a tactic for ally selection. The simulations indicated that gaming is favored when players possess above-average skill and when environmental risk coevolves with population skill; otherwise, gaming tends to drift or disappear. Together, these studies suggest that the social effects of gaming are context-dependent and may not emerge uniformly across game types or interaction settings. The modeling results highlight that risk, skill, and reliability of performance cues are key parameters for understanding the potential evolutionary role of gaming in alliance formation. Future work should integrate long-term interactions, participants’ skill levels, and different game ecologies to clarify when gaming strengthens social bonds and when it does not.

The choice of an academic major is a critical vocational decision, influenced by personality and other individual differences. While personality traits and sex are known predictors, the role of sexual orientation remains less explored, particularly in diverse cultural contexts. This study examined how HEXACO personality traits predict academic major choice among Brazilian undergraduate students (N = 706), predominantly recruited from public universities. Using penalized multinomial logistic regression, we modeled the likelihood of enrollment in three domains: Social Sciences and Humanities (SSH), Life and Health Sciences (LHS), and Science, Technology, Engineering, and Mathematics (STEM). Higher Openness to Experience was associated with a greater likelihood of choosing SSH over LHS and with increased likelihood of SSH overall. Lower Extraversion predicted a higher likelihood of STEM enrollment. No independent effects of sex or sexual orientation were observed once personality traits were modeled simultaneously. These findings suggest that academic specialization may be structured by cognitive-exploratory traits (Openness) and social engagement tendencies (Extraversion) rather than by demographic characteristics per se. Academic major choice appears to reflect multidimensional person-field fit processes rather than single-factor determinants within this sample context.

There is robust evidence to the effect that homosexual individuals have systematically less offspring. The sexually antagonistic genes hypothesis claims that this fitness-related disadvantage of homosexual individuals is compensated by their other-sex relatives exhibiting greater fertility than the relatives of straight individuals. It would allow explain how genetic variants associated with homosexuality persist in the human population. Nevertheless, previous studies yielded conflicting results and, moreover, they focused almost solely on the fertility of gay men's relatives. We present the results of a large preregistered study based on data on fertility of both gay men's and lesbian women's relatives. We have analyzed the fertility and biological kin fertility of 693 gay men, 843 straight men, 265 lesbian women, and 331 straight women from Czechia and Slovakia. As expected, gay men and lesbian women sired significantly less offspring than straight individuals. However, we also found no evidence supporting the sexually antagonistic genes hypothesis, i.e., no difference between the fertility of other-sex relatives of homosexual and heterosexual individuals. Interestingly, though, paternal grandparents of gay men had more offspring than the paternal grandparents of straight men did. The mothers of lesbian women had a higher fertility than the mothers of straight women, but that could be attributed to intervening effects, such as the excess of older brothers in homosexual individuals. Our results suggest that mechanisms other than those predicted by the sexually antagonistic genes hypothesis are involved in the evolution of human homosexual orientation.

A prospective partner’s sexual history provides important information that can be used to minimise mating-related risks. Such information includes the number of past sexual partners, which has an inverse relationship with positive suitor evaluation. However, sexual encounters with new partners vary in frequency over time, providing an additional dimension of context not previously considered. Across three studies (N = 5,331) with 15 samples, we demonstrate that the impact of past partner number on a suitor’s desirability as a long-term partner varies as a function of distribution over time. Using graphical representations of a suitor’s sexual history, we found that past partner number effects were smaller when the frequency of new sexual encounters decreased over time. This moderation effect was stronger, and often curvilinear, when past partner numbers were higher. We replicated these findings in 11 countries from five world regions. Sex differences were minimal and inconsistent pointing to a lack of a sexual double standards. Sociosexuality (openness to casual sex) was a consistent moderator and tended to mute the sexual history effects. These findings suggest that people not only attend to a potential long-term mate’s quantity of sexual partners, but also the context surrounding these encounters such as pattern and timing. Together, the findings raise the possibility of an evolved mechanism for managing mating risks present in both sexes and across populations and adds nuance to a contentious topic of public interest.

Mental simulation theories of language comprehension propose that people automatically create mental representations of objects mentioned in sentences. Mental representation is often measured with the sentence-picture verification task, wherein participants first read a sentence that implies the object property (i.e., shape and orientation). Participants then respond to an image of an object by indicating whether it was an object from the sentence or not. Previous studies have shown matching advantages for shape, but findings concerning object orientation have not been robust across languages. This registered report investigated the match advantage of object orientation across 18 languages in nearly 4,000 participants. The preregistered analysis revealed no compelling evidence for a match advantage for orientation across languages. Additionally, the match advantage was not predicted by mental rotation scores. In light of these findings, we discuss the implications for current theory and methodology surrounding mental simulation.

Decades of research support the generalization that human males tend to be more aggressive than females. However, most of that research has examined aggression between unrelated individuals. Data drawn from 24 societies around the globe (n = 4,013) indicate that this generalization does not hold in the context of sibling relationships. In retrospective self-reports, females report being at least as aggressive as males toward their siblings, often more so. This holds for direct as well as indirect aggression, and for aggression between adult siblings as well as aggression that occurred during childhood. Consistent with prior research on sex differences, males reported engaging in more direct aggression toward nonkin than did females in the majority of societies. The results suggest that the dynamics of aggression within the family are different from those outside of it, and ultimately that understanding the role of sex in aggressive tendencies depends on context and target.