Testosterone rapidly increases men's emotion-based dehumanization of a conservatively dressed woman.

Past research has found that sexualized women are often dehumanized (i.e., attributed reduced human qualities). However, the mechanisms contributing to such dehumanization remain poorly understood. In this pre-registered experiment involving a within-subject, placebo-controlled, cross-over design, we tested whether testosterone contributes to men's (N = 120, age range: 18-38 years) dehumanization of women. After administration of intranasal testosterone or placebo gel, men watched a video of a woman wearing either modest (i.e., conservative) or revealing (i.e., sexualized) clothing (between-subjects factor) and then completed three subtle dehumanization tasks, measuring emotion-based, personality-based, and perceptual dehumanization. We hypothesized that testosterone would increase dehumanization, especially for men who watched the "sexualized-clothing" video. Instead, we found that, while men engaged in emotion-based dehumanization toward the sexualized woman both when they had testosterone and placebo, testosterone increased emotion-based dehumanization toward the conservatively dressed woman. Other forms of dehumanization were not affected by testosterone. We also explored whether personality (e.g., dominance) and biological (e.g., CAG repeat polymorphism) traits that have been found to moderate the effects of testosterone on some social behaviors also moderated the effects examined here, but we did not find any significant moderations. Overall, this experiment revealed a novel physiological mechanism affecting emotion-based dehumanization.

Relatively rapid effects of testosterone on men's ratings of female attractiveness depend on relationship status and the attractiveness of stimulus faces.

Attractiveness judgements influence desires to initiate and maintain romantic relationships. Testosterone also predicts relationship initiation and maintenance; such effects may be driven by the hormone's modulation of attractiveness judgements, but no studies have investigated causal (and situation-dependent) effects of the hormone on these judgements. Using a placebo-controlled cross-over design, our preregistered analyses revealed order- and relationship- dependent effects: single heterosexual men judged the women as more appealing when testosterone was administered first (and placebo second), but marginally less appealing when placebo was administered first (and testosterone second). In a more complex model incorporating the women's attractiveness (as rated by an independent set of observers), however, we show that testosterone increases the appeal of women -but this effect depends upon the men's relationship status and the women's attractiveness. In partnered men (n = 53) who tend to derogate attractive alternatives (by rating them as less appealing), testosterone countered this effect, boosting the appeal of these attractive alternatives. In single men (n = 53), conversely, testosterone increased the appeal of low-attractive women. These differential effects highlight the possibility of a newly discovered mechanism whereby testosterone promotes male sexual reproduction through different routes depending on relationship status, promoting partner up- rather than down-grading when partnered and reducing choosiness when single. Further, such effects were relatively rapid [within 85 (±5) minutes], suggesting a potential non-genomic mechanism of action.

Preliminary evidence that brief exposure to vaccination-related internet memes may influence intentions to vaccinate against COVID-19.

Despite global efforts to rapidly distribute COVID-19 vaccines, early estimates suggested that 29-35% of the population were hesitant/unwilling to receive them. Countering such vaccine hesitancy is thus an important priority. Across two sets of online studies (total n = 1584) conducted in the UK before (August-October 2020) and immediately after the first effective vaccine was publicly announced (November 10-19, 2020), brief exposure (<1 min) to vaccination memes boosted the potentially life-saving intention to vaccinate against COVID-19. These intention-boosting effects, however, weakened once a COVID-19 vaccine became a reality (i.e., after the announcement of a safe/effective vaccine), suggesting meme-based persuasion may be context-dependent. These findings thus represent preliminary evidence that naturally circulating memes may-under certain circumstances-influence public intentions to vaccinate, although more research regarding this context-specificity, as well as the potential psychological mechanisms through which memes act, is needed.

Exploratory Analysis of the Relationship between Social Identification and Testosterone Reactivity to Vicarious Combat.

Testosterone (T) fluctuates in response to competitive social interactions, with the direction of change typically depending on factors such as contest outcome. Watching a competition may be sufficient to activate T among fans and others who are invested in the outcome. This study explores the change in T associated with vicarious experiences of competition among combat sport athletes viewing a teammate win or lose and assesses how individual differences in social identification with one's team relates to these patterns of T reactivity. Twenty-six male combat athletes completed a social identity questionnaire on a neutral day. Later, salivary samples (assayed for T) were obtained before and after athletes viewed a video of a teammate engaged in a formal contest. T reactivity to viewing a teammate compete varied among participants in both the magnitude and direction of change, independent of contest outcome. Individual differences in cognitive centrality, a core feature of social identification, showed a strong positive relationship with T reactivity, particularly if their teammate won. Initial findings suggest that dominance-linked androgen responses associated with watching a teammate win a competition might depend on the belief that team membership is central to one's own identity. These exploratory results in a small sample of combat athletes should be interpreted with caution. Uncovering the role of social group dynamics in influencing T responses to competition is particularly important in light of the evolutionary history of coalitional combat in humans.

Not giving up: Testosterone promotes persistence against a stronger opponent.

Recent research suggests that when we lack a sense of control, we are prone to motivational failures and early quitting in competitions. Testosterone, on the other hand, is thought to boost competitiveness. Here we investigate the interaction between these factors, testing the testosterone's potential to enhance persistence in a competition against a stronger opponent, depending on experimentally manipulated perceived control. Healthy participants were administered a single dose of testosterone or placebo. They first underwent a task designed to either induce low or high perceived control and then entered a costly competition against a progressively stronger opponent that they could quit at any time. In the placebo group, men with low perceived control quitted twice as early as those with high perceived control. Testosterone countered this effect, making individuals with low control persist in the competition for as long as those with high perceived control, and did so also despite raising participants' explicit awareness of the opponents' advantage. This psychoendocrinological effect was not modulated by basal cortisol levels, CAG repeat polymorphism of the androgen receptor gene, or trait dominance. Our results provide the first causal evidence that testosterone promotes competitive persistence in humans and demonstrate that this effect depends on the psychological state elicited prior to the competition, broadening our understanding of the complex relationships between testosterone and social behaviors.

Inducing illusory control ensures persistence when rewards fade and when others outperform us.

Persisting even when the rewards of continued effort are fading is essential for achieving long-term goals, skills, and good health, alike. Yet, we often quit when things get hard. Here, we tested whether augmenting the feeling of control through external measures increases persistence under such discouraging circumstances. In two laboratory experiments, we first induced illusory control by manipulating the base-rate of positive outcomes and then tested the effect of this elevation of participants' perceived control upon their persistence under diminishing returns and in a competition against a stronger opponent. Induced illusory control significantly enhanced people's persistence in both of these motivationally challenging situations. Our findings demonstrate that motivation is dependent upon perceived, rather than objective, control, and reveal that this can be leveraged to counteract quitting behavior when things get hard, for instance in rehabilitation, physical activity interventions, or other training settings.

Testosterone reduces the threat premium in competitive resource division.

Like other animals, humans are sensitive to facial cues of threat. Recent evidence suggests that we use this information to dynamically calibrate competitive decision-making over resources, ceding more to high-threat individuals (who appear more willing/able to retaliate) and keeping more from low-threat individuals. Little is known, however, about the biological factors that support such threat assessment and decision-making systems. In a pre-registered, double-blind, placebo-controlled, cross-over testosterone administration study ( n = 118 men), we show for the first time that testosterone reduces the effects of threat on decision-making: participants ceded more resources to high-threat (versus low-threat) individuals (replicating the 'threat premium'), but this effect was blunted by testosterone, which selectively reduced the amount of resources ceded to those highest in threat. Thus, our findings suggest that testosterone influences competitive decision-making by recalibrating the integration of threat into the decision-making process.

Using a Psychopharmacogenetic Approach To Identify the Pathways Through Which-and the People for Whom-Testosterone Promotes Aggression.

Little is known about the neurobiological pathways through which testosterone promotes aggression or about the people in whom this effect is observed. Using a psychopharmacogenetic approach, we found that testosterone increases aggression in men ( N = 308) with select personality profiles and that these effects are further enhanced among those with fewer cytosine-adenine-guanine (CAG) repeats in exon 1 of the androgen receptor (AR) gene, a polymorphism associated with increased AR efficiency. Testosterone's effects were rapid (~30 min after administration) and mediated, in part, by subjective reward associated with aggression. Testosterone thus appears to promote human aggression through an AR-related mechanism and to have stronger effects in men with the select personality profiles because it more strongly upregulates the subjective pleasure they derive from aggression. Given other evidence that testosterone regulates reward through dopaminergic pathways, and that the sensitivity of such pathways is enhanced among individuals with the personality profiles we identified, our findings may also implicate dopaminergic processes in testosterone's heterogeneous effects on aggression.

Sleep restriction alters reactive aggressive behavior and its relationship with sex hormones.

Few studies have experimentally manipulated sleep to study its effect on aggressive behavior. The current study examined how reactive aggression was affected by having sleep restricted to 4-hours on a single night, a level of disruption commonly experienced. Both rested and sleep-restricted participants completed the Point Subtraction Aggression Paradigm (PSAP), a laboratory task in which participants seek to earn points, are provoked by a fictitious opponent stealing their points, and may choose to steal points in response. Logistic mixed-effect models were used to investigate the effect of sleep restriction and the role of sex hormones on the odds of choosing to steal. For men, and women in the luteal phase of the menstrual cycle, sleep restriction did not result in significant changes reactive aggression, although the patterns of aggressive behavior appeared less reactive and retaliatory in nature. For women in the follicular phase of the menstrual cycle, sleep restriction was associated with higher levels of reactive aggression. For both men and women in the luteal phase, sleep restriction disrupted an association between hormone change over the task (testosterone and estradiol, respectively) and reactive aggression that was observed in their control participants. In addition, higher testosterone before the PSAP in men was associated with maintaining a high level of stealing over the task. These results indicate a complex dynamic in which sex hormones and sleep interact to predict aggressive behavior in response to provocation.

Effect of exogenous testosterone on cooperation depends on personality and time pressure.

The social heuristic hypothesis posits that human cooperation is an intuitive response that is expressed especially under conditions of time-constraint. Conversely, it proposes that for individuals given an opportunity for reflection, cooperation is more likely to be curtailed by an optimizing process calibrated to maximize individual benefit in a given situation. Notably, the steroid hormone testosterone has also been implicated in intuitive decision-making, including both prosocial and anti-social behaviors, with effects strongest in men with particular dispositional characteristics. This raises the possibility that increased testosterone may augment the effects predicted by the social heuristic hypothesis, particularly among men higher in specific dispositional characteristics (dominance, impulsivity, independent self-construal: high risk for testosterone-induced antisocial behavior). Here, in a testosterone administration study with a relatively large sample of men (N = 400), we test this possibility in a double-blind, placebo-controlled paradigm, with men randomly assigned to play a one-shot public goods game either under time-pressure (forced intuition) or with a time delay (forced reflection). Results revealed that within the placebo group, time-pressure (versus forced delay) increased cooperation among low risk men, but decreased cooperation among high risk men. Testosterone further moderated this pattern by abolishing the time-pressure effect in low risk men and-in high risk men-reversing the effect by selectively reducing offers (compared to placebo) under forced delay. This is the first evidence that testosterone and personality can interact with time-pressure and delay to predict human cooperation.

Detecting implicit cues of aggressiveness in male faces in revictimized female PTSD patients and healthy controls.

Victimized women are thought to have impairments in identifying risk and to have dysfunctional reactions to threatening situations, which increase the risk for revictimization. To investigate possible deficits in revictimized women, we used a method examining women's perceptions of an implicit facial cue of aggressiveness - the facial Width-to-Height Ratio (fWHR). We tested whether revictimized women show impairments in detecting aggressiveness in male faces by neglecting cues of fWHR and choosing a smaller preferred distance to men. Fifty-two revictimized PTSD patients and 52 healthy controls provided ratings of aggressiveness and attractiveness for 65 photographed men and chose their preferred distance towards 11 pictured men. Multiple regression analyses indicated that revictimized women do not show impairments in perceiving and reacting to cues of aggression accurately. Hierarchical linear models, however, indicated that revictimized women rated all men as less aggressive. Revictimized women with histories of intimate partner violence (IPV) rated men with larger fWHRs and higher values of actual aggression to be more attractive than did revictimized women without IPV histories. A reduced appraisal of threat signals as threatening and an attraction to wider-faced and more aggressive men might increase the risk for revictimization.

Human social neuroendocrinology: Review of the rapid effects of testosterone.

Contribution to Special Issue on Fast effects of steroids. It is well documented that testosterone concentrations change rapidly within reproductively relevant contexts (e.g., competition, mate-seeking). It has been argued that such rapid changes in testosterone may serve to adaptively fine-tune ongoing and/or future social behaviour according to one's social environment. In this paper, we review human correlational and experimental evidence suggesting that testosterone fluctuates rapidly in response to competition and mate-seeking cues, and that such acute changes may serve to modulate ongoing and/or future social behaviours (e.g., risk-taking, competitiveness, mate-seeking, and aggression). Some methodological details, which limit interpretation of some of this human work, are also discussed. We conclude with a new integrative model of testosterone secretion and behaviour, the Fitness Model of Testosterone Dynamics. Although we focus primarily on human aggression in this review, we also highlight research on risk-taking, competitiveness, and mate-seeking behaviour.

Force versus fury: Sex differences in the relationships among physical and psychological threat potential, the facial width-to-height ratio, and judgements of aggressiveness.

Individuals with larger facial width-to-height ratios (FWHRs) are judged as more threatening, and engage in more threat-related behavior, than do individuals with smaller FWHRs. Here we identified components of threat potential that are related to the FWHR. In Study 1, the FWHR was correlated positively with physical threat potential (bicep size) in women and with both physical and psychological (anger proneness) threat potential in men. Behavioral aggression was measured in a subset of these participants using the Point Subtraction Aggression Paradigm (costly aggression) and a Money Allocation Task (non-costly aggression). Psychological (but not physical) threat potential predicted non-costly aggression and physical (but not psychological) threat potential predicted costly aggression. In Study 2, a separate set of participants judged the anger proneness, strength, or aggressiveness of male participants photographed in Study 1. Participants' judgements of all three characteristics were associated with the FWHR, and there were sex differences in how aggressiveness was conceptualized (for women, aggressiveness was associated with anger proneness, for men, aggressiveness was associated with strength). These results are consistent with the hypothesis that the FWHR may be an adaptation to cue the threat potential of men.

The facial width-to-height ratio determines interpersonal distance preferences in the observer.

Facial width-to-height ratio (fWHR) is correlated with a number of aspects of aggressive behavior in men. Observers appear to be able to assess aggressiveness from male fWHR, but implications for interpersonal distance preferences have not yet been determined. This study utilized a novel computerized stop-distance task to examine interpersonal space preferences of female participants who envisioned being approached by a man; men's faces photographed posed in neutral facial expressions were shown in increasing size to mimic approach. We explored the effect of the men's fWHR, their behavioral aggression (measured previously in a computer game), and women's ratings of the men's aggressiveness, attractiveness, and masculinity on the preferred interpersonal distance of 52 German women. Hierarchical linear modelling confirmed the relationship between the fWHR and trait judgements (ratings of aggressiveness, attractiveness, and masculinity). There were effects of fWHR and actual aggression on the preferred interpersonal distance, even when controlling statistically for men's and the participants' age. Ratings of attractiveness, however, was the most influential variable predicting preferred interpersonal distance. Our results extend earlier findings on fWHR as a cue of aggressiveness in men by demonstrating implications for social interaction. In conclusion, women are able to accurately detect aggressiveness in emotionally neutral facial expressions, and adapt their social distance preferences accordingly.

Exogenous Testosterone Rapidly Increases Aggressive Behavior in Dominant and Impulsive Men.

BACKGROUND: Although traditional wisdom suggests that baseline levels of testosterone (T) promote aggressive behavior, decades of research have produced findings that have been largely weak and inconsistent. However, more recent experimental work suggests that exogenous administration of T rapidly potentiates amygdala and hypothalamus responses to angry facial expressions. Notably, these brain regions are rich in androgen receptors and play a key role in modulating aggressive behavior in animal models. METHODS: The present experiment extends this work by examining whether acutely increasing T potentiates aggressive behavior in men. In a double-blind, placebo-controlled, between-subject design, healthy adult men (n = 121) were administered either T or placebo, and subsequently engaged in a well-validated decision-making game that measures aggressive behavior in response to social provocation. In light of prior correlational research, we also assessed the extent to which T's effects on aggressive behavior would depend on variability in trait dominance and/or trait self-control. RESULTS: Exogenous T on its own did not modulate aggressive behavior. However, T's effects on aggression were strongly influenced by variation in trait dominance and trait self-control. Specifically, T caused an increase in aggressive behavior, but only among men scoring relatively high in trait dominance or low in trait self-control. CONCLUSIONS: These findings are the first to demonstrate that T can rapidly (within 60 minutes) potentiate aggressive behavior, but only among men with dominant or impulsive personality styles.

The Point Subtraction Aggression Paradigm as a laboratory tool for investigating the neuroendocrinology of aggression and competition.

A contribution to a special issue on Hormones and Human Competition.The ease of measuring steroids in saliva has led to an increase in investigating their role in competition and aggression in laboratory settings and using behavioral measures of aggression. We review here the Point-Subtraction-Aggression-Paradigm (PSAP) as a measure of costly aggression and we compare and contrast the PSAP to other aggression measures. We describe our use of the PSAP, highlighting how it can be modified to investigate a broad array of experimental questions. We review studies that have investigated neuroendocrine function and the PSAP, and we conclude that across studies the relationship between fluctuations in testosterone and PSAP aggression scores are directionally positive, and are likely specific to men. Investigations of other neuroendocrine measures and the PSAP are fewer, limiting conclusions that can be drawn for other hormones. We provide two versions of the PSAP that can be used with E-PRIME® software for researchers interested in this measure for their laboratories.

Effects of competition outcome on testosterone concentrations in humans: An updated meta-analysis.

A contribution to a special issue on Hormones and Human Competition. Since Archer's (2006) influential meta-analysis, there has been a major increase in the number of studies investigating the effect of competition outcome on testosterone reactivity patterns in humans. Despite this increased research output, there remains debate as to whether competition outcome modulates testosterone concentrations. The present paper examines this question using a meta-analytic approach including papers published over the last 35years. Moreover, it provides the first meta-analytic estimate of the effect of competition outcome on testosterone concentrations in women. Results from a meta-analysis involving 60 effect sizes and >2500 participants indicated that winners of a competition demonstrated a larger increase in testosterone concentrations relative to losers (D=0.20)-an effect that was highly heterogeneous. This 'winner-loser' effect was most robust in studies conducted outside the lab (e.g., in sport venues) (D=0.43); for studies conducted in the lab, the effect of competition outcome on testosterone reactivity patterns was relatively weak (D=0.08), and only found in studies of men (D=0.15; in women: D=-0.04). Further, the 'winner-loser' effect was stronger among studies in which pre-competition testosterone was sampled earlier than (D=0.38, after trim and fill correction) rather than within (D=0.09) 10min of the start of the competition. Therefore, these results also provide important insight regarding study design and methodology, and will be a valuable resource for researchers conducting subsequent studies on the 'winner loser' effect.

Evidence from Meta-Analyses of the Facial Width-to-Height Ratio as an Evolved Cue of Threat.

The facial width-to-height ratio (FWHR) is the width of the face divided by the height of the upper face. There is mixed evidence for the hypothesis that the FWHR is a cue of threat and dominance in the human face. We conducted a systematic review and meta-analyses of all peer-reviewed studies (and 2 unpublished studies) to estimate the magnitude of the sex difference in the FWHR, and the magnitude of the relationship between the FWHR and threatening and dominant behaviours and perceptions. Studies were eligible for inclusion if the authors reported an analysis involving the FWHR. Our analyses revealed that the FWHR was larger in men than in women (d = .11, n = 10,853), cued judgements of masculinity in men (r = .35, n of faces = 487; n of observers = 339), and was related to body mass index (r = .31, n = 2,506). Further, the FWHR predicted both threat behaviour in men (r = .16, n = 4,603) and dominance behaviour in both sexes (r = .12, n = 948) across a variety of indices. Individuals with larger FWHRs were judged by observers as more threatening (r = .46, n of faces = 1,691; n of observers = 2,076) and more dominant (r = .20, n of faces = 603; n of observers = 236) than those with smaller FWHRs. Individuals with larger FWHRs were also judged as less attractive (r = -.26, n of faces = 721; n of observers = 335), especially when women made the judgements. These findings provide some support for the hypothesis that the FWHR is part of an evolved cueing system of intra-sexual threat and dominance in men. A limitation of the meta-analyses on perceptions of threat and dominance were the low number of stimuli involving female and older adult faces.

Costly retaliation is promoted by threats to resources in women and threats to status in men.

What motivates people to act against their own self-interest? In men, what seems to be irrational decision-making in the short-term may be explained by other long-term benefits; thus retaliation may not be motivated by tangible costs, but instead intangible psychological variables (e.g., status threats). In contrast, there is evidence that women are more sensitive to tangible costs than are men. In Experiment 1, using the Point Subtraction Aggression Paradigm (PSAP), we tested the prediction that in men, the frequency of provocation, and not the monetary loss (tangible cost), would be associated with retaliation, whereas women would be sensitive to the tangible costs. In keeping with the prediction, women (n = 80) who incurred greater tangible costs (irrespective of frequency) retaliated with more costly punishment, whereas men (n = 90) who were provoked more frequently (irrespective of tangible costs) retaliated with more costly punishment. In Experiment 2, we directly investigated whether women were more sensitive to threats to resources and men were more sensitive to threats to status, as suggested by the results of Experiment 1. Women's (n = 53) retaliation was greater when they reported it to be a means to protect their resources, and men's (n = 35) retaliation was greater when they reported it to be a means to protect their status. Thus, these results identify psychological variables that guide retaliation that is costly to the actor. Consistent with evolutionary perspectives, concerns about status appear to drive costly retaliatory behavior more so in men than in women.

Facial Structure Predicts Sexual Orientation in Both Men and Women.

Biological models have typically framed sexual orientation in terms of effects of variation in fetal androgen signaling on sexual differentiation, although other biological models exist. Despite marked sex differences in facial structure, the relationship between sexual orientation and facial structure is understudied. A total of 52 lesbian women, 134 heterosexual women, 77 gay men, and 127 heterosexual men were recruited at a Canadian campus and various Canadian Pride and sexuality events. We found that facial structure differed depending on sexual orientation; substantial variation in sexual orientation was predicted using facial metrics computed by a facial modelling program from photographs of White faces. At the univariate level, lesbian and heterosexual women differed in 17 facial features (out of 63) and four were unique multivariate predictors in logistic regression. Gay and heterosexual men differed in 11 facial features at the univariate level, of which three were unique multivariate predictors. Some, but not all, of the facial metrics differed between the sexes. Lesbian women had noses that were more turned up (also more turned up in heterosexual men), mouths that were more puckered, smaller foreheads, and marginally more masculine face shapes (also in heterosexual men) than heterosexual women. Gay men had more convex cheeks, shorter noses (also in heterosexual women), and foreheads that were more tilted back relative to heterosexual men. Principal components analysis and discriminant functions analysis generally corroborated these results. The mechanisms underlying variation in craniofacial structure--both related and unrelated to sexual differentiation--may thus be important in understanding the development of sexual orientation.