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Gangestad et al. (this issue) recently published alternative analyses of our open data to investigate whether women show ovulatory shifts in preferences for men’s bodies. They  argue that a significant three-way interaction between log-transformed hormones, a  muscularity component, and women’s relationship status provides evidence for the ovulatory shift hypothesis. Their conclusion is opposite to the one we previously reported (Jünger et al., 2018). Here, we provide evidence that Gangestad et al.’s differing conclusions are contaminated by overfitting, clarify reasons for deviating from our preregistration in some aspects, discuss the implications of data-dependent re-analysis, and report a multiverse analysis which provides evidence that their reported results are not robust. Further, we use the current debate to contrast the risk of prematurely concluding a null effect against the risk of shielding hypotheses from falsification. Finally, we discuss the benefits and challenges of open scientific practices, as contested by Gangestad et al., and conclude with implications for future studies.

Recent studies suggest that both facial and bodily dominance promote high status positions and predict status-seeking behaviors such as aggression and social dominance. An evolutionarily relevant context in which associations between these dominance signals and status outcomes may be prevalent are face-to-face status contests. The present study examined whether facial and bodily dominance predicted success in dyadic competitions (one physical discipline, arm wrestling, and three nonphysical disciplines) in men (N = 125) in a controlled laboratory setting. Men’s bodies and faces were independently rated for physical dominance, and associations of these ratings with contest outcomes as well as mediating and moderating variables (such as physical strength, body height, trait dominance, baseline and reactive testosterone) were examined. Both facial and bodily dominance positively predicted success in the physical discipline, mediated by physical strength, but not in the three nonphysical disciplines. Our findings demonstrate that facial and bodily physical dominance may be honest signals for men’s formidability and hence status potential, at least in a physically competitive context.

Animal social bonds are defined as stable, equitable and strong affiliative and cooperative relationships similar to human friendships. Just as human friendships, social bonds are thought to function as alliances that generate adaptive benefits via support in critical situations. In humans, similarity in many sociodemographic, behavioural and intrapersonal characteristics leads to trust and is predictive of friendships. Specifically, personality homophily, that is the tendency of individuals to form social bonds with others who have a similar personality, may increase predictability and facilitate trust and reciprocity among partners with compatible behavioural tendencies. While evidence for social bonding in nonhumans is accumulating, far less is known about its predictors. Here, personality homophily effects on the formation and maintenance of social bonds are shown in twenty-four wild male Assamese macaques (Macaca assamensis), at Phu Khieo Wildlife Sanctuary, Thailand. Dyadic bond strength increased with increased similarity in the trait Connectedness (i.e. frequent and diverse neighbours in 5m proximity and pronounced social tolerance, as high rates of friendly approaches to and by others). To differentiate whether homophily indeed predicted bond formation or whether bonded males’ personalities became more similar over time, we tested the stability of the connectedness traits in a subset of immigrating males that had to form new bonds. Connectedness in these males remained stable suggesting that males do not adapt their personality to their partner. Our results support the idea of a shared evolutionary origin of homophily as a partner choice strategy in human and non-human animals. The main selective advantage of personality similarity in animal social bonds may result from a more reliable cooperation among individuals with similar cooperative behavioural tendencies.

In nonhuman animals, individuals of the same sex and age differ in their behavior patterns consistently across time, comparable with human personality differences. To draw conclusions about the adaptive value of behavior traits, it is essential to study them in the wild where animals are subject to the ecological pressures that promoted the evolution of behavior strategies. This study was conducted in the Phu Khieo Wildlife Sanctuary, Thailand, on 4 groups of habituated wild Assamese macaques by observers who had familiarized themselves with the subjects over the course of an ongoing long-term study. We used a multimethod approach enabling the most comprehensive understanding of variation in stable interindividual differences in a species-typical ecological setting. We combined trait ratings (TRs), assessed with observer-report questionnaires (54-item Hominoid Personality Questionnaire) of 107 individuals of diverse age-sex classes, with behavior codings (BCs) of 24 adult males. We found male and female personality constructs to be congruent and examined reliability and construct validity. Combining trait rating and behavioral coding, we found two solutions with five factors to best describe the personality structure of the males: one structure comprised the dimensions Gregariousness BC , Aggressiveness BC , Sociability BC and Vigilance BC , complemented by a Confidence TR domain and the other structure Opportunism TR , Confidence TR , Friendliness TR , Activity TR complemented with Vigiance BC . We discuss our findings with regard to the importance of construct validity and reproducibility in the context of method development and standardization in nonhuman animal personality research.

Research on links between peoples’ personality traits and their voices has primarily focused on other peoples’ personality judgments about a target person based on a target person’s vocal characteristics, particularly voice pitch. However, it remains unclear whether individual differences in voices are linked to actual individual differences in personality traits, and thus whether vocal characteristics are indeed valid cues to personality. Here, we investigate how the personality traits of the Five Factor Model of Personality, sociosexuality, and dominance are related to measured fundamental frequency (voice pitch) and formant frequencies (formant position). For this purpose, we conducted a secondary data analysis of a large sample (2,217 participants) from eleven different, independent datasets with a Bayesian approach. Results suggest substantial negative relationships between voice pitch and self-reported sociosexuality, dominance and extraversion in men and women. Thus, personality might at least partly be expressed in people’s voice pitch. Evidence for an association between formant frequencies and self-reported personality traits is not compelling but remains uncertain. We discuss potential underlying biological mechanisms of our effects and suggest a number of implications for future research.

With the advent of online and app-based studies, researchers in psychology are making increasing use of repeated subjective reports. The new methods open up opportunities to study behavior in the field and to map causal processes, but they also pose new challenges. Recent work has added initial elevation bias to the list of common pitfalls; here, higher negative states (i.e., thoughts and feelings) are reported on the first day of assessment than on later days. This article showcases a new approach to addressing this and other measurement reactivity biases. Specifically, we employed a planned missingness design in a daily diary study of more than 1,200 individuals who were assessed over a period of up to 70 days to estimate and adjust for measurement reactivity biases. We found that day of first item presentation, item order, and item number were associated with only negligible bias: items were not answered differently depending on when and where they were shown. Initial elevation bias may thus be more limited than has previously been reported or it may act only at the level of the survey, not at the item level. We encourage researchers to make design choices that will allow them to routinely assess measurement reactivity biases in their studies. Specifically, we advocate the routine randomization of item display and order, as well as of the timing and frequency of measurement. Randomized planned missingness makes it possible to empirically gauge how fatigue, familiarity, and learning interact to bias responses.

Objectives: The assessment of men’s physical strength is an important part of human social perception, for which observers rely on different kinds of cues. However, besides previous studies being limited in considerable ways, as yet there is no comprehensive investigation of a range of somatometric measures in relation to both objectively measured and observer-perceived physical strength using valid stimuli. Methods: We examined observer-perceptions of physical strength from 3D body scans of N = 165 men, the usage and validity of somatometric measures as cues to strength, differences between strength ratings from stimuli presented on computer monitors versus in real-life size using a projector, and between male and female observers. Results: A medium-sized correlation between measured and perceived strength was found, partly mediated by target men’s chest-to-hip ratio, body density, ankle girth, height, upper arm and forearm girth. No significant differences between men’s and women’s strength perceptions or the method of stimuli presentation (computer monitor vs. projector) emerged. Conclusions: Our findings suggest that men’s physical strength can be assessed with moderate accuracy from 3D body models and that some somatometric measures represent valid cues, which were used by observers, positively predicting both measured and perceived physical strength.

Few studies have examined birth order effects on personality in countries that are not Western, educated, industrialized, rich, and democratic (WEIRD). However, theories have generally suggested that interculturally universal family dynamics are the mechanism behind birth order effects, and prominent theories such as resource dilution would predict even stronger linear effects in poorer countries. Here, we examine a subset of up to 11 188 participants in the Indonesian Family Life Survey to investigate whether later‐borns differ from earlier‐borns in intelligence, educational attainment, Big Five, and risk aversion. Analyses were performed using within‐family designs in mixed‐effects models. In model comparisons, we tested for linear and non‐linear birth order effects as well as for possible interactions of birth order and sibship size. Our estimated effect sizes are consistent with the emerging account of birth order as having relatively little impact on intelligence, Big Five, and risk aversion. We found a non‐linear pattern for educational attainment that was not robust to imputation of missing data and not aligned with trends in WEIRD countries. Overall, the small birth order effects reported in other studies appear to be culturally specific.

Mate preferences and mating-related behaviors are hypothesized to change over the menstrual cycle in ways that function to increase reproductive fitness. Results of recent large-scale studies suggest that many of these hormone-linked behavioral changes are less robust than was previously thought. One specific hypothesis that has not yet been subject to a large-scale test is the proposal that women’s preference for associating with male kin is down-regulated during the ovulatory (high-fertility) phase of the menstrual cycle. Consequently, we used a longitudinal design to investigate the relationship between changes in women’s steroid hormone levels and their perceptions of faces experimentally manipulated to possess kinship cues (Study 1). Analyses suggested that women viewed men’s faces displaying kinship cues more positively (i.e., more attractive and trustworthy) when estradiol-to-progesterone ratio was high. Since estradiol-to-progesterone ratio is positively associated with conception risk during the menstrual cycle, these results directly contradict the hypothesis that women’s preference for associating with male kin is down-regulated during the ovulatory (high-fertility) phase of the menstrual cycle. Study 2 employed a daily diary approach and found no evidence that women reported spending less time in the company of male kin or thought about male kin less often during the fertile phase of the menstrual cycle. Thus, neither study found evidence that inbreeding avoidance is up-regulated during the ovulatory phase of the menstrual cycle.

Open-source software improves the reproducibility of scient ific research. Because existing open-source tools often do not offer dedicated support for longit udinal data collection on phones and  computers, we built formr, a study framework  that enables researchers to conduct both simple s urveys and more intricate Studies. With automated email and text message reminders that can be sent according to any schedule, longitudinal and experience-sampling studies become easy to implement. By integrating a web-based application programming interf ace for the statistical pro gramming language R via OpenCPU, formr allows researchers to use a familiar programming language to enable complex features. These can range from adaptive testing, to graphical and interactive feedback, to integration with non-survey data sources such as self-trackers or online s ocial network data. Here we showcase three studies created in formr: a study of couples with dyadic feedback; a longitudinal study over months, which included social networks and peer and partner ratings; and a diary study with daily invitations sent out by text message and email and extensive feedback on intraindividual patterns.

The current project measures personality across cultures, for the first time using a forced-choice (or idiographic) assessment instrument - the California Adult Q-set (CAQ). Correlations among the average personality profiles across 13 countries (total N = 2,370) ranged from r = .69 to r = .98. The most similar averaged personality profiles were between USA/Canada; the least similar were South Korea/Russia/Poland and China/Russia. The Czech Republic had the most homogeneous personality descriptions and South Korea had the least. In further analyses, country differences in CAQ-derived Big Five scores were compared to results obtained from previous research using nomothetic Likert scales (i.e., the NEO; the BFI). The Big Five templates produced generally similar findings to previous research com-paring the Big Five across countries using Likert-type methods.

Women's mating psychology may have evolved to track reproductive conditions, including conception risk, across and between ovulatory cycles. Alternatively, within-woman correlations between mating psychology and ovarian hormones may be byproducts of between-women relationships. Here, we examined associations between steroid hormones and two facets of sexual psychology with putatively different adaptive functions, sociosexual orientation and general sexual desire, in a sample of naturally cycling women (NC; n = 348, 87 of whom completed 2 sessions) and hormonally contracepting women (HC; n = 266, 65 of whom completed 2 sessions). Across two sessions, increases in estradiol predicted elevated sociosexual desire in NC women, and this relationship was stronger in women whose progesterone simultaneously decreased across sessions. Changes in hormones were not associated with changes in general sexual desire. Between-subjects differences in testosterone robustly, positively predicted sociosexuality and general sexual desire among NC women. Hormones were not consistently related to changes or differences in sexual psychology among HC women. The present results are consistent with testosterone contributing to individual differences, or modulating relatively long-term changes, in women's mating psychology. Further, our within-woman findings are consistent with the hypothesis that shifts in women's mating psychology may function to secure genetic benefits, and that these shifts are not byproducts of between-women associations.

As is the case for humans, it has long been thought that nonhuman primates can be described in terms of their personality. Scientific observations that support this view include the presence of individual differences in social behavior and that they are relatively stable throughout life. Consequently, individuals are constrained in their behavioral flexibility when dealing with various environmental challenges. Still, the variation among individuals during development suggests that the environment influences how primates behave. Research in fields including psychology, behavior genetics, and behavioral ecology have tried to identify the mechanisms responsible for this interplay of behavioral stability and change. In this review we integrate theories and findings from research on humans and nonhuman primates that highlight how and to what extent genetic and environmental contributions shape the development of social behavior. To do so we first provide an overview and define what is meant by mean level and rank-order change of behavior. We then review explanations of behavioral stability and change, focusing on the role of genetic effects, how environmental circumstances influence behavioral variation throughout development, and how genetic and environmental influences may interact to produce this variation. Finally, we point to future research directions that could help us to further understand the development of social behavior in primates from within a behavior genetics framework.

The theory of facultative calibration, which explains personality differences as  responses to variation in other phenotypic traits of individuals, received mixed results throughout the last years. Whereas there is strong evidence that individual differences in human behavior are correlated with the self-perception of other traits, it still needs to be questioned whether they are also adjusted to objective differences in body condition (i.e. formidability). In two independent studies (N 1  = 119 men and 124 women, N 2  = 165 men) we tested hypotheses of facultative personality calibration in an integrative way, assessing various outcomes of previous studies in the same samples (including Anger Proneness, Extraversion, Neuroticism, Narcissism, Shyness, Vengefulness, and Sociosexual Orientation). Formidability was derived from assessments of physical strength and various anthropometric measures from full-body 3D scans and paired with measures of self-perceived and other-rated physical attractiveness (based on rotating morphometric 3D body models and facial photographs). We could replicate positive correlations with self-perceived attractiveness across outcomes, though these were not corroborated by more objective assessments of attractiveness: an effect of other-rated attractiveness was clearly not supported in our results for either sex, regardless of the personality outcome. Anthropometric measures and physical strength were also largely unrelated to personality, with the exception of Extraversion, Utility of Personal Aggression, and Sociosexual Orientation. While the two samples differed in their results for domain-level Extraversion, at least the Extraversion facets Activity and Assertiveness were related to strength and masculinity in men. For Sociosexual Orientation the results of our two samples varied more substantially, a positive association was only present in Study 2. Future studies need to clarify whether formidability, potentially an indicator of genetic quality for males, enhances their orientation and success in short-term mating. Furthermore we propose longitudinal twin-difference studies as means to evaluate the theory of personality recalibration in a more controlled manner.

Objectives The dual-hormone hypothesis suggests that associations of testosterone (T) with certain behavioral tendencies are stronger when cortisol (C) levels are low simultaneously. A range of studies provided supporting evidence for TxC interaction effects, for example on dominance and risk-taking behaviors. However, concerning perceptions of facial characteristics the evidence is mixed, with a recent study reporting a positive association between perceived facial dominance and T among men with higher C. Methods We sought to further examine links of observer-rated facial attractiveness, dominance and health (based on photographs of N = 165 men) with baseline T, competition-induced T reactivity, and their interaction with baseline C. Results There was some evidence that baseline T and the interaction of T reactivity with  baseline C positively predicted facial dominance, however these were not robust when including control variables. Conclusions Since no effects were found for perceived attractiveness and health, our results suggest that associations of perceived facial characteristics with baseline T, T reactivity and their interactions with baseline C are rather weak.

Objectives Facial masculinity, as for example measured by the facial width-to-height ratio (fWHR) or the global facial masculinity index, has been associated with a vast  range of behavioural traits, including dominance and aggression. Further, facial masculinity is thought to be influenced by testosterone (T) levels as an underlying mechanism. However, a recent meta-analysis on fWHR and T levels provided non-significant associations in men, which we wanted to examine further in men and additionally in women. Methods We examined whether fWHR and global facial masculinity are positively associated with salivary baseline T and T reactivity in 140 men (age 18-34 years), as well as with salivary baseline T and hair T concentrations in 151 women (age 18-35 years). Results No associations of salivary baseline T, T reactivity or hair T levels with fWHR or global facial masculinity were observed. Additional analyses revealed sex differences in sexual dimorphism in fWHR and global facial masculinity: men had generally higher global facial masculinity compared to women, but unexpectedly a lower fWHR. Conclusions Overall, our results provide further evidence that neither fWHR nor global facial masculinity are related to T levels and question earlier findings on male-biased sexual dimorphism in fWHR.

Event history calendars (EHCs) are popular tools for retrospective data collection. Originally conceptualized as face-to-face interviews, EHCs contain various questions about the respondents’ autobiography in order to use their experiences as cues to facilitate remembering. For relationship researchers, EHCs are particularly valuable when trying to reconstruct the relational past of individuals. However, while many studies are conducted online nowadays, no online adaptation of the EHC is available yet. In this tutorial, we provide detailed instructions on how to implement an online EHC for the reconstruction of romantic relationship histories within the open source framework formr. We exemplify on ways to customize the online EHC and provide a template for researchers to adapt the tool for their own purposes.

Are estrous mate preference shifts robust? This question is the subject of controversy within human evolutionary sciences. For nearly two decades, mate preference shifts across the ovulatory cycle were considered an important feature of human sexual selection, directing women’s attention towards mates with indicators of “good genes” in their fertile phase, when conception is possible. However, several recent studies on masculine faces, bodies or behaviors have failed to find evidence supporting this account, known as the good genes ovulatory shift hypothesis. Furthermore, evidence that preferences for masculine characteristics in men’s voices are related to women’s cycle phase and hormonal status is still equivocal. Here, we report two independent within-subject studies from different labs with large sample sizes (N = 202 tested twice in Study 1; N = 157 tested four times in Study 2) investigating cycle shifts in women’s preferences for masculine voices. In both studies, hormonal status was assessed directly using salivary assays of steroid hormones. We did not find evidence for effects of cycle phase, conception risk or steroid hormone levels on women’s preferences for masculine voices. Rather, Study 2 suggests cycle shifts in women’s attraction to men’s voices regardless of masculine characteristics, though Study 1 provided only partly evidence for such attraction shifts. Women’s relationship status and self-reported stress did not moderate these findings, and the hormonal pattern that influences these shifts remains somewhat unclear. We consider how future work can clarify the mechanisms underlying psychological changes across the ovulatory cycle.