Examining the Fraternal Birth Order Effect and Sexual Orientation: Insights from an East European Population.

The development of human sexual orientation remains a complex and multifaceted subject. It is often studied but its origins continue to elude us. In this preregistered study, our primary objective was to demonstrate the fraternal birth order effect (FBOE), which assumes a higher prevalence of older brothers in gay men than in their straight counterparts and which has also been recently recorded in lesbian women. Our second aim was to explore any potential impact of the FBOE on anal-erotic role orientation (AERO), both in gay and straight men. Our study sample included 693 gay men, 843 straight men, 265 lesbian women, and 331 straight women from Czechia and Slovakia. Employing a conventionally parameterized logistic regression model, we substantiated the FBOE among both gay men (OR = 1.35 for maternal older brothers) and lesbian women (OR = 1.71). These outcomes were confirmed by a more nuanced parameterization recently proposed by Blanchard (2022). Nonmaternal older brothers did not exhibit a significant influence on their younger brothers' sexual orientation. Contrary to some earlier reports, however, our data did not establish the FBOE as exclusive to gay men with the receptive AERO. Furthermore, our observations indicated a lower offspring count for mothers of gay men compared to mothers of straight men. Emphasizing the positive FBOE outcomes, we acknowledge the need for caution regarding the various options that can be used to estimate the familial influences on sexual orientation.

What Do Different People Look for in a Partner? Effects of Sex, Sexual Orientation, and Mating Strategies on Partner Preferences.

Partner preferences are an important differential in relationship formation and evolutionary fitness, and vary according to individual, ecological, and social factors. In this study, we evaluated the variation in preference for intelligence, kindness, physical attractiveness, health, and socioeconomic level among individuals of different sexes and sexual orientations in a Brazilian sample. We analyzed the preference scores of 778 heterosexual, bisexual, and homosexual men and women in three budgeted mate design tasks (low vs. medium vs. high budget) and their association with sociosexuality, attachment styles, homogamy, and willingness to engage in short- and long-term relationships. Results indicated a global trait preference order, with intelligence ranking first, followed by kindness, physical attractiveness, health, and lastly by socioeconomic status. Typical sex differences were observed mostly within the heterosexual group, and specific combinations of sex and sexual orientation were linked to variation in preference for physical attractiveness, kindness, and socioeconomic status. We also found unique associations of the other variables with partner preferences and with willingness to engage in short- or long-term relationships. By exploring the partner preferences of non-heterosexual individuals from a Latin American country, an underrepresented group in evolutionary psychology research, our results help understand the universal and specific factors that guide partner preferences and human sexual behavior.

Effects of Voice Pitch on Social Perceptions Vary With Relational Mobility and Homicide Rate.

Fundamental frequency ( fo) is the most perceptually salient vocal acoustic parameter, yet little is known about how its perceptual influence varies across societies. We examined how fo affects key social perceptions and how socioecological variables modulate these effects in 2,647 adult listeners sampled from 44 locations across 22 nations. Low male fo increased men's perceptions of formidability and prestige, especially in societies with higher homicide rates and greater relational mobility in which male intrasexual competition may be more intense and rapid identification of high-status competitors may be exigent. High female fo increased women's perceptions of flirtatiousness where relational mobility was lower and threats to mating relationships may be greater. These results indicate that the influence of fo on social perceptions depends on socioecological variables, including those related to competition for status and mates.

Validation of the Short Version (TLS-15) of the Triangular Love Scale (TLS-45) across 37 Languages.

Love is a phenomenon that occurs across the world and affects many aspects of human life, including the choice of, and process of bonding with, a romantic partner. Thus, developing a reliable and valid measure of love experiences is crucial. One of the most popular tools to quantify love is Sternberg's 45-item Triangular Love Scale (TLS-45), which measures three love components: intimacy, passion, and commitment. However, our literature review reveals that most studies (64%) use a broad variety of shortened versions of the TLS-45. Here, aiming to achieve scientific consensus and improve the reliability, comparability, and generalizability of results across studies, we developed a short version of the scale-the TLS-15-comprised of 15 items with 5-point, rather than 9-point, response scales. In Study 1 (N = 7,332), we re-analyzed secondary data from a large-scale multinational study that validated the original TLS-45 to establish whether the scale could be truncated. In Study 2 (N = 307), we provided evidence for the three-factor structure of the TLS-15 and its reliability. Study 3 (N = 413) confirmed convergent validity and test-retest stability of the TLS-15. Study 4 (N = 60,311) presented a large-scale validation across 37 linguistic versions of the TLS-15 on a cross-cultural sample spanning every continent of the globe. The overall results provide support for the reliability, validity, and cross-cultural invariance of the TLS-15, which can be used as a measure of love components-either separately or jointly as a three-factor measure.

Homosexual Courtship in Young Wild Capuchin Monkeys: A Case Study.

In primates, many species exhibit same-sex sexual behaviors (SSB), defined as "genital contact or genital manipulation between same-sex individuals." Several sociosexual functions have been proposed, including proceptivity enhancement, receptivity reduction, dominance assertion, practice for heterosexual copulation, tension regulation, reconciliation, and alliance formation. Capuchin monkeys are known for their rich and flexible sexual behavioral repertoire and elaborated courtships. At present, the few reports of SSB in capuchin monkeys (genera Sapajus and Cebus) focused on mounting. Here, we describe the case observed in a population of wild yellow-breasted capuchin monkeys (Sapajus xanthosternos) in which two young males, aged 5-6 years and 19 months, performed a 15-min uninterrupted sequence of courtship behaviors and mounting. Comparing with a previously established ethogram of 20 behaviors typical for heterosexual behavior of tufted capuchins, we show that these males performed 16 of them. Thus, SSBs are already present in the repertoire of young individuals and the practice may serve to create or strengthen bonds. Although same-sex mounting and genital inspection are common in capuchins' play and other social interactions, the almost entire array of courtship behaviors has never been observed in youngsters. Additionally, this example supports the notion that primate (homo)sexual behavior is not limited to genitalia and copulation, since the observed courtship included diverse behaviors different from genital contact. Thus, we propose a broader definition of sexual behavior.

Individual Differences in How Desirable People Think They Are as a Mate.

Mate value is an important concept in mate choice research although its operationalization and understanding are limited. Here, we reviewed and evaluated previously established conceptual and methodological approaches measuring mate value and presented original research using individual differences in how people view themselves as a face-valid proxy for mate value in long- and short-term contexts. In data from 41 nations (N = 3895, Mage = 24.71, 63% women, 47% single), we tested sex, age, and relationship status effects on self-perceived mate desirability, along with individual differences in the Dark Triad traits, life history strategies, peer-based comparison of desirability, and self-reported mating success. Both sexes indicated more short-term than long-term mate desirability; however, men reported more long-term mate desirability than women, whereas women reported more short-term mate desirability than men. Further, individuals who were in a committed relationship felt more desirable than those who were not. Concerning the cross-sectional stability of mate desirability across the lifespan, in men, short- and long-term desirability rose to the age of 40 and 50, respectively, and decreased afterward. In women, short-term desirability rose to the age of 38 and decreased afterward, whereas long-term desirability remained stable over time. Our results suggest that measuring long- and short-term self-perceived mate desirability reveals predictable correlates.

Mating Performance and Singlehood Across 14 Nations.

Adult individuals frequently face difficulties in attracting and keeping mates, which is an important driver of singlehood. In the current research, we investigated the mating performance (i.e., how well people do in attracting and retaining intimate partners) and singlehood status in 14 different countries, namely Austria, Brazil, China, Greece, Hungary, Italy, Japan, Peru, Poland, Russia, Spain, Turkey, the UK, and Ukraine (N = 7,181). We found that poor mating performance was in high occurrence, with about one in four participants scoring low in this dimension, and more than 57% facing difficulties in starting and/or keeping a relationship. Men and women did not differ in their mating performance scores, but there was a small yet significant effect of age, with older participants indicating higher mating performance. Moreover, nearly 13% of the participants indicated that they were involuntarily single, which accounted for about one-third of the singles in the sample. In addition, more than 15% of the participants indicated that they were voluntarily single, and 10% were between-relationships single. We also found that poor mating performance was associated with an increased likelihood of voluntary, involuntary, and between-relationships singlehood. All types of singlehood were in higher occurrence in younger participants. Although there was some cross-cultural variation, the results were generally consistent across samples.

Evolution of Artistic and Athletic Propensities: Testing of Intersexual Selection and Intrasexual Competition.

Since Darwin proposed that human musicality evolved through sexual selection, empirical evidence has supported intersexual selection as one of the adaptive functions of artistic propensities. However, intrasexual competition has been overlooked. We tested their relative importance by investigating the relationship between the self-perceived talent/expertise in 16 artistic and 2 sports modalities and proxies of intersexual selection (i.e., mate value, mating and parenting efforts, sociosexuality, and number of sexual partners) and intrasexual competition (i.e., aggressiveness, intrasexual competitiveness) in heterosexuals. Participants were 82 Brazilian men, 166 Brazilian women, 146 Czech men, and 458 Czech women (Mage = 26.48, SD = 7.12). Factor analysis revealed five factors: Literary-arts (creative writing, humor, acting/theater/film, poetry, storytelling), Visual-arts (painting/drawing, sculpting, handcrafting, culinary arts, architecture design), Musical-arts (playing/instruments, singing, dance, whistling), Circus-arts (juggling, acrobatics), and Sports (individual, collective). Multivariate General Linear Model (GLM) showed more associations of the arts to intersexual selection in women and to intrasexual selection in men, and overall more relationships in women than in men. In women, literary and musical-arts were related to elevated inter- and intrasexual selections proxies, visual and circus-arts were related to elevated intersexual selection proxies, and sports were related to intrasexual selection proxies. In men, literary-arts and sports were related to elevated inter- and intrasexual selection proxies, musical-arts were related to intrasexual proxies, and circus-arts were related to intersexual proxies; visual-arts did not have predictors. Although present in both sexes, each sexual selection component has different relative importance in each sex. Artisticality functions to attract and maintain long/short-term partners, and to compete with mating rivals.

Jealousy Is Influenced by Sex of the Individual, Their Partner, and Their Rival.

Jealousy is an affective state activated by a perceived threat to a valued relationship by a third party. On average, males report higher distress about their partner's sexual extra-pair involvement, while females show higher emotional jealousy. These sex differences are specific to heterosexuals and to contexts with potential reproductive costs. We tested the effect of sex and sexual orientation of the individual, and sex of the partner and potential rival on sexual versus emotional jealousy. Sexual orientation was operationalized as a willingness to form long-term relationships with men, women, or both. Heterosexual, homosexual, and bisexual males (N = 416) and females (N = 1328) from Brazil, Chile, and Portugal responded to the Sexual vs. Emotional Jealousy Scale and then ranked their distress to four hypothetical scenarios: sexual or emotional involvement of their partner with a male or a female rival. This is the first study to simultaneously test for an effect of self, partner, and rival sex on jealousy: bisexual individuals responded twice, about a hypothetical female and about a male partner. Individuals were most preoccupied with their partner's emotional relationship with a rival of the same sex as the respondent. Heterosexual males reported higher sexual jealousy than the other groups, but did not differ from bisexual men responding about female partners. Bisexual females were more upset by sexual extra-pair involvement of their female (versus male) partners with a male rival. Thus, jealousy was influenced by sex and sexual orientation of the individuals, sex of the partners, and also by sex of the rivals: same-sex rivals were perceived as most threatening. This suggests that besides being a strategy to maintain a primary relationship, jealousy is particularly sensitive to same-sex competitors, being an intra-sexual competition strategy.

Comparing Different Typologies of Physical Activities With a Focus on Motivation.

There are numerous classifications of physical activities (PAs). However, they lack precise grouping criteria and tend to vary according to each author. Among other factors, the individual's level of motivation is considered an important aspect of PA maintenance. In this study, we aimed to (1) compare several PAs according to intrinsic (Interest, Enjoyment, and Competence) and extrinsic (Appearance, Fitness/Health, and Social) motives and (2) analyze PAs with and without previous grouping to explore which PAs are more similar based on the different motivational subscales. We recruited 1,421 physically active Brazilian participants (mean age = 26.83, SD = 10.49). The participants stated which PA they practiced most frequently, and they answered the revised motivation for PA measure. The data were analyzed with multivariate general linear models and Kruskal-Wallis. We found that some PAs consistently differed from others regarding motivational subscales. For example, participants practicing Walking showed less Interest/Enjoyment and Competence motives than participants engaged in several other PAs. Pilates was highlighted by a particularly low level of Social motivation in comparison to other PAs. Furthermore, using the previously suggested categorization of PAs, we also showed consistent distinctions considering each motivational subscale. Specifically, one group of PA (categorized as more Complex, Team, Vigorous, Hybrid, and Combative) scored higher on intrinsic motivation, while the other group of activities (categorized as more Organized, Individual, Moderate, Strength, and Rhythmic) scored higher on Appearance and Fitness/Health motives. Our results thus provide initial evidence for possible new methods of grouping PA types that can improve maintenance behavior using motivation as a grouping factor.

The Evolution of Playfulness, Play and Play-Like Phenomena in Relation to Sexual Selection.

By conceptualizing Sexual Selection, Darwin showed a way to analyze intra-specific individual differences within an evolutionary perspective. Interestingly, Sexual Selection is often used to investigate the origins of sports, arts, humor, religion and other phenomena that, in several languages, are simply called "play." Despite their manifested differences, these phenomena rely on shared psychological processes, including playfulness. Further, in such behaviors there is usually considerable individual variability, including sex differences, and positive relationship with mating success. However, Sexual Selection is rarely applied in the study of play, with exception to what is concerned as infant training behavior for adult sex roles. We offer an integrated grounding of playful phenomena aligning evolutionary propositions based on sexual selection, which might stimulate further exploration of playfulness within evolutionary perspective.

The contrasting effects of body image and self-esteem in the makeup usage.

Women wearing makeup are perceived by others as more attractive, competent, dominant, and more socially prestigious. Individuals differ in how much and how frequently they use makeup. Some studies show that women with lower self-esteem use more makeup, probably to hide imperfections. However, women with higher self-esteem can also use makeup to attract attention. This study verified whether social and general self-esteem and body image are associated with makeup usage in Brazilian women. We collected data from 1,483 women (Mage = 31.08; SD = 11.15) about body image (appearance orientation and appearance evaluation), social self-esteem, general self-esteem, and makeup usage (frequency of makeup usage, time spent applying makeup per day, and money spent on makeup per month). Appearance orientation positively predicted frequency of makeup usage, time spent applying makeup, and money spent on makeup, whereas appearance evaluation inversely predicted money spent on makeup per month. Social self-esteem and general self-esteem also positively predicted money spent on makeup, but in different directions. The results suggest that the significance given to appearance and social interactions are importantly associated with makeup usage in women.

Interações sexuais entre indivíduos do mesmo sexo: um olhar evolucionista / Same-sex sexual interactions: an evolutionary perspective / Interactions sexuelles entre personnes du même sexe: une perspective évolutionniste / Interacciones sexuales entre individuos del mismo sexo: una visión evolucionista

Resumo Sob uma perspectiva evolutiva, as interações sexuais entre indivíduos do mesmo sexo foram por muito tempo consideradas um grande paradoxo. Isso por terem persistido no decorrer das gerações apesar de supostamente não oferecerem benefícios reprodutivos diretos, reduzindo, aparentemente, a aptidão individual. Apesar disso, são comuns em muitas espécies animais. Neste artigo, revisaremos algumas das hipóteses funcionais que tentam resolver esse quebra-cabeça evolutivo. Algumas dessas hipóteses consideram essas interações adaptativas, o que significa que trariam benefícios para os indivíduos. Outras as consideram neutras, derivadas de características realmente vantajosas. Por fim, existem as que consideram essas interações como não-adaptativas e potencialmente prejudiciais aos indivíduos. Ao final, abordaremos uma hipótese revolucionária que, de forma inédita, questiona se as interações sexuais envolvendo exclusivamente indivíduos de sexos diferentes seriam realmente o estado basal do comportamento sexual.

Abstract From an evolutionary point of view, same-sex sexual interactions have long been considered a major paradox. This is because they have persisted throughout generations despite, presumably, not offering direct reproductive benefits and, apparently, reducing individual fitness. Nonetheless, same-sex sexual interactions are common in many animal species. This paper reviews some functional hypotheses that seek to solve this evolutionary puzzle: some consider it adaptative, meaning that these behaviors would bring benefits to individuals; others see it as a neutral by-product of other advantageous characteristics. A third branch understand same-sex sexual interactions to be non-adaptative and potentially deleterious to individuals. Finally, this paper discusses a revolutionary hypothesis that, unprecedently, questions whether sexual interactions involving exclusively individuals of the opposite sex are in fact the basal state of sexual behavior.

Résumé Du point de vue de l'évolution, les interactions sexuelles entre personnes du même sexe ont longtemps été considérées comme un grand paradoxe majeur. En effet, elles ont persisté au fil des générations bien qu'elles n'offrent vraisemblablement pas d'avantages reproductifs directs et qu'elles réduisent apparemment la valeur adaptative individuelle. Néanmoins, sont courantes chez de nombreuses espèces animales. Cet article passe en revue certaines hypothèses fonctionnelles qui cherchent à résoudre cette énigme évolutive : certaines considèrent les interactions comme adaptatives, ce qui signifie que ces comportements apporteraient des avantages aux individus ; d'autres voient les comme un sous-produit neutre d'autres caractéristiques avantageuses. Une troisième branche les comprend comme étant non-adaptatives et potentiellement délétères pour les individus. Enfin, on discute d'une hypothèse révolutionnaire qui, sans précédent, remet en question le fait que les interactions sexuelles impliquant exclusivement des individus du sexe opposé serait l'état ancestral du comportement sexuel.

Resumen Desde una perspectiva evolutiva, las interacciones sexuales entre individuos del mismo sexo han sido consideradas por mucho tiempo como una enorme paradoja. Esto es debido a que han persistido generación tras generación a pesar de, supuestamente, no ofrecer beneficios reproductivos directos, reduciendo, aparentemente, la aptitud individual. Sin embargo, son comunes en muchas especies de animales. En este artículo repasaremos algunas de las hipótesis funcionales que intentan resolver este rompecabezas evolutivo. Algunas de estas hipótesis consideran que estas interacciones son adaptativas, lo que trae benefícios a los individuos. Otras hipótesis las consideran neutras, derivadas de características realmente ventajosas. Mientras que otras consideran estas interacciones como no adaptativas y potencialmente perjudiciales para los individuos. Por último, expondremos una hipótesis revolucionaria que, de manera inédita, cuestiona si las interacciones sexuales que involucran exclusivamente a individuos de diferentes sexos son realmente el estado basal del comportamiento sexual.

Voice modulation: from origin and mechanism to social impact.

Research on within-individual modulation of vocal cues is surprisingly scarce outside of human speech. Yet, voice modulation serves diverse functions in human and nonhuman nonverbal communication, from dynamically signalling motivation and emotion, to exaggerating physical traits such as body size and masculinity, to enabling song and musicality. The diversity of anatomical, neural, cognitive and behavioural adaptations necessary for the production and perception of voice modulation make it a critical target for research on the origins and functions of acoustic communication. This diversity also implicates voice modulation in numerous disciplines and technological applications. In this two-part theme issue comprising 21 articles from leading and emerging international researchers, we highlight the multidisciplinary nature of the voice sciences. Every article addresses at least two, if not several, critical topics: (i) development and mechanisms driving vocal control and modulation; (ii) cultural and other environmental factors affecting voice modulation; (iii) evolutionary origins and adaptive functions of vocal control including cross-species comparisons; (iv) social functions and real-world consequences of voice modulation; and (v) state-of-the-art in multidisciplinary methodologies and technologies in voice modulation research. With this collection of works, we aim to facilitate cross-talk across disciplines to further stimulate the burgeoning field of voice modulation. This article is part of the theme issue 'Voice modulation: from origin and mechanism to social impact (Part I)'.

Makeup and Its Application Simulation Affect Women's Self-Perceptions.

Appearance modification is ancient, universal and influences other and self-perceptions. It has been rarely addressed how expectation of appearance modification would affect women's self-perception. We analyzed self-assessments of women without makeup and after having makeup professionally applied at four increasing levels (light, moderate, heavy 1, and heavy 2 makeup). In the simulation phase, women were treated with colorless cosmetics. Fifty Brazilian women (Mage = 24.26 years; SD = 5.53) rated themselves on attractiveness, health, self-esteem, femininity, satisfaction with appearance, age, dominance, confidence, and competence in all experimental conditions. Women in the simulation phase considered themselves more feminine, healthier, and with higher self-esteem than without makeup. In the real makeup phases, these ratings were higher than in the simulation phase. Appearance satisfaction and attractiveness did not differ between simulation and the real makeup phases, both being higher than without makeup. Confidence increased only in real makeup phases, but there was no effect on competence. Thus, real appearance modification and/or an expectation thereof can differently affect specific domains of self-evaluation.

COVID-19 Pandemic on Fire: Evolved Propensities for Nocturnal Activities as a Liability Against Epidemiological Control.

Humans have been using fire for hundreds of millennia, creating an ancestral expansion toward the nocturnal niche. The new adaptive challenges faced at night were recurrent enough to amplify existing psychological variation in our species. Night-time is dangerous and mysterious, so it selects for individuals with higher tendencies for paranoia, risk-taking, and sociability (because of security in numbers). During night-time, individuals are generally tired and show decreased self-control and increased impulsive behaviors. The lower visibility during night-time favors the partial concealment of identity and opens more opportunities for disinhibition of self-interested behaviors. Indeed, individuals with an evening-oriented chronotype are more paranoid, risk-taking, extraverted, impulsive, promiscuous, and have higher antisocial personality traits. However, under some circumstances, such as respiratory pandemics, the psychobehavioral traits favored by the nocturnal niche might be counter-productive, increasing contagion rates of a disease that can evade the behavioral immune system because its disease cues are often nonexistent or mild. The eveningness epidemiological liability hypothesis presented here suggests that during the COVID-19 pandemic, the evening-oriented psychobehavioral profile can have collectively harmful consequences: there is a clash of core tendencies between the nocturnal chronotype and the recent viral transmission-mitigating safety guidelines and rules. The pandemic safety protocols disrupt much normal social activity, particularly at night when making new social contacts is desired. The SARS-CoV-2 virus is contagious even in presymptomatic and asymptomatic individuals, which enables it to mostly evade our evolved contagious disease avoidance mechanisms. A growing body of research has indirectly shown that individual traits interfering with social distancing and anti-contagion measures are related to those of the nocturnal chronotype. Indeed, some of the social contexts that have been identified as superspreading events occur at night, such as in restaurants, bars, and nightclubs. Furthermore, nocturnal environmental conditions favor the survival of the SARS-CoV-2 virus much longer than daytime conditions. We compare the eveningness epidemiological liability hypothesis with other factors related to non-compliance with pandemic safety protocols, namely sex, age, and life history. Although there is not yet a direct link between the nocturnal chronotype and non-compliance with pandemic safety protocols, security measures and future empirical research should take this crucial evolutionary mismatch and adaptive metaproblem into account, and focus on how to avoid nocturnal individuals becoming superspreaders, offering secure alternatives for nocturnal social activities.