Testosterone, gender identity and gender-stereotyped personality attributes

Sex/gender differences in personality associated with gender stereotyped behavior are widely studied in psychology yet remain a subject of ongoing debate. Exposure to testosterone during developmental periods is considered to be a primary mediator of many sex/gender differences in behavior. Extensions of this research has led to both lay beliefs and initial research about individual differences in basal testosterone in adulthood relating to "masculine" personality. In this study, we explored the relationships between testosterone, gender identity, and gender stereotyped personality attributes in a sample of over 400 university students (65 % female assigned at birth). Participants provided ratings of their self-perceived masculinity and femininity, resulting in a continuous measure of gender identity, and a set of agentic and communal personality attributes. A saliva sample was also provided for assay of basal testosterone. Results showed no compelling evidence that basal testosterone correlates with gender-stereotyped personality attributes or explains the relationship between sex/gender identity and these attributes, across, within, or covarying out sex assigned at birth. Contributing to a more gender diverse approach to assessing sex/gender relationships with personality and testosterone, our continuous measure of self-perceived masculinity and femininity predicted additional variance in personality beyond binary sex and showed some preliminary but weak relationships with testosterone. Results from this study cast doubt on the activational testosterone-masculinity hypothesis for explaining sex differences in gender stereotyped traits and within-sex/gender variation in attributes associated with agency and communality.

No Compelling Evidence that Self-Reported Personality Traits Explain Basal Testosterone and Cortisol’s Associations with Status-Relevant Behavior

Objective

A goal of behavioral neuroendocrinology is to understand how basal hormone levels relate to behavior. Studies of human participants sometimes measure self-reported personality traits, in addition to or instead of direct behavioral observation. Although personality traits often predict their respective behaviors, whether personality explains hormone-behavior relationships remains unclear.

Methods

We obtained data from eight previous studies (total N = 985) that examined baseline testosterone and cortisol as predictors of status-relevant behavior (competitiveness, dominance, risk-taking, aggression, affiliation, and social status). We tested whether the previously reported hormone-behavior relationships are mediated by self-reported personality traits (e.g., trait dominance, prestige, extraversion). As a secondary research question, we also tested whether trait dominance moderated the testosterone-behavior relationships.

Results

As expected, self-reported personality traits often predicted status-relevant behaviors, but there was little evidence that traits also correlated with basal testosterone or the testosterone × cortisol interaction. Across all eight studies, personality traits did not significantly mediate hormone-behavior relationships. Indeed, the effect sizes of the hormone-behavior relationships were robust to the inclusion of personality traits as covariates. Further, we did not find strong or consistent evidence that trait dominance moderates the testosterone-behavior association.

Conclusion

Results suggest that basal testosterone and cortisol predict status-related behavior independent of self-reported personality. We discuss how these results may have broader implications for the physiological mechanisms by which testosterone and cortisol influence behavior, a process that could be unconscious and automatic. We also discuss alternative explanations, limitations, and future directions.

The causal effect of testosterone on men's competitive behavior is moderated by basal cortisol and cues to an opponent's status: Evidence for a context-dependent dual-hormone hypothesis

Testosterone has been theorized to direct status-seeking behaviors, including competitive behavior. However, most human studies to date have adopted correlational designs, and findings across studies are inconsistent. This experiment (n = 115) pharmacologically manipulated men's testosterone levels prior to a mixed-gender math competition and examined basal cortisol (a hormone implicated in stress and social avoidance) and context cues related to an opponent's perceived status (an opponent's gender or a win/loss in a prior competition) as factors that may moderate testosterone's impact on competitive behavior. We test and find support for the hypothesis that testosterone given to low-cortisol men evokes status-seeking behavior, whereas testosterone given to high-cortisol men evokes status-loss avoidance. In the initial rounds of competition, testosterone's influence on competitive decisions depended on basal cortisol and opponent gender. After providing opponent-specific win-lose feedback, testosterone's influence on decisions to reenter competitions depended on basal cortisol and this objective cue to status, not gender. Compared to placebo, men given exogenous testosterone who were low in basal cortisol showed an increased tendency to compete against male and high-status opponents relative to female and low-status opponents (status-seeking). Men given exogenous testosterone who were high in basal cortisol showed the opposite pattern-an increased tendency to compete against female and low-status opponents relative to male and high-status opponents (status-loss avoidance). These results provide support for a context-dependent dual-hormone hypothesis: Testosterone flexibly directs men's competitive behavior contingent on basal cortisol levels and cues that signal an opponent's status. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Testosterone fluctuations in response to a democratic election predict partisan attitudes toward the elected leader

Intergroup competitions such as democratic elections can intensify intergroup polarization and conflict. Partisan attitudes toward the elected leader can also shift from before to after an election, but the biology underlying these attitudinal shifts remains largely unknown. An important factor could be the hormone testosterone, which is theorized to fluctuate during competition and to influence status seeking. In a naturalistic study of 113 registered voters, we measured changes in testosterone levels and attitudes toward the winner of the 2012 US Presidential Election. We found that supporters of the losing candidate (Mitt Romney) showed acute increases in testosterone levels compared to supporters of the winner (Barack Obama) on the evening of Election Day. Supporters of the losing candidate also demonstrated flatter diurnal testosterone slopes on Election Day that persisted up to two days after the election. Furthermore, greater increases in acute testosterone levels and flatter diurnal slopes among supporters of the losing candidate were associated with less positive evaluations of the winning candidate. These testosterone-moderated attitudinal shifts observed in the days after the election showed a directionally similar pattern with a weaker effect size six months later. Finally, we confirmed that the main results were robust to alternative data analytic choices using multiverse specification curve analysis. The findings from this paper suggest that hormonal responses to large-scale intergroup competitions may shape how we perceive our elected leaders, shedding light on the biology of intergroup relations.

Testosterone reactivity to competition and competitive endurance in men and women

Transient shifts in testosterone occur during competition and are thought to positively influence dominance behavior aimed at enhancing social status. However, individual differences in testosterone reactivity to status contests have not been well-studied in relation to real-time expressions of competitive behavior among men and women. This research tests the association between changes in endogenous testosterone levels during competition and performance in terms of competitive endurance. Participant sex, social presence, and relative status outcomes (e.g., winning vs. losing) are tested as moderators of this relationship. In two studies, men and women (total N = 398) competed in the competitive will task (timed weight-holding) either individually or in the presence of an opponent (Study 1) or as a team with and without the presence of a competitor team (Study 2). Results showed a positive relationship between testosterone reactivity and performance for men, particularly those who won or ranked highest among their group - with increasing testosterone predicting better performance and decreasing testosterone predicting worse performance. For women, the effect only emerged among individuals who competed in dyads and lost. In Study 2, an exploratory mediation analysis revealed that individual differences in trait dominance predicted both testosterone reactivity to competition and task performance, with testosterone reactivity (moderated by sex and status outcome) partially explaining the direct relationship between dominance-related traits and behavior. Our goal was to examine testosterone reactivity in relation to real-time competitive effort and highlight the potential role of this relationship in explaining how individual differences in trait dominance produce competitive behavior.

Beyond the challenge hypothesis: The emergence of the dual-hormone hypothesis and recommendations for future research

The challenge hypothesis makes specific predictions about the association between testosterone and status-seeking behaviors, but the findings linking testosterone to these behaviors are often inconsistent. The dual-hormone hypothesis was developed to help explain these inconsistencies. Specifically, according to this hypothesis, testosterone's association with status-seeking behavior depends on levels of cortisol. Here, we (1) describe the dual-hormone hypothesis in relation to the challenge hypothesis; (2) review recent studies that tested the dual-hormone hypothesis as well as meta-scientific evidence of heterogeneous dual-hormone findings across studies; (3) discuss potential explanations for this heterogeneity, including methodological considerations, contextual factors, and individual differences; and (4) provide recommendations for new work aimed at testing and extending the dual-hormone hypothesis.

Unstable correspondence between salivary testosterone measured with enzyme immunoassays and tandem mass spectrometry

Although some studies reveal that saliva handling and storage practices may influence salivary testosterone concentrations measured with immunoassays, the effect of these method factors on the validity of testosterone immunoassays remains unknown. The validity of immunoassays can be assessed by comparing hormone concentrations measured with immunoassays to a standard reference method: liquid chromatography tandem mass spectrometry (MS). We previously reported the correspondence between salivary testosterone measured with enzyme immunoassays (EIAs) and with MS when there was less variance in (or more control over) method factors related to saliva handling and storage across measurement methods (Welker et al., 2016). In the present study, we expanded the original dataset and compared the correspondence between Salimetrics EIAs and MS when there was greater variance in (or less control over) method factors across EIAs and MS (high method variance), to when there was less variance in these factors (low method variance). If variance in these method factors impacts the validity of testosterone measurement, then the EIA-MS correspondence should be stronger when method variance is low compared to when it is high. Our results contradicted this hypothesis: Salimetrics EIA-MS correspondence was stronger when variance in method factors was high compared to when it was low. The composite average correlation across both method variance comparisons provides an updated estimate of Salimetrics EIA-MS correspondence, but the instability in this correspondence may pose challenges to the reproducibility of psychoneuroendocrinology research. We discuss possible explanations for the surprising pattern of results and provide recommendations for future research.

Stress, cortisol, and social hierarchy

We review the literature on the relationships between cortisol, stress, and various forms of social status, concluding that cortisol (and stress) is typically elevated when one chronically lacks, or may soon lose, status. Moreover, cortisol is lower when status is higher, as long as that status is stable, enhances one's sense of control, and does not also substantially increase one's responsibilities. Because cortisol is both an output (stress indicator) and input (cause of behavioral inhibition), this low cortisol may be both a cause and consequence of stable status. Altogether, the cortisol-status relationship depends not just on one's status but on what that status means for the individual (e.g. How frequent and severe are stressors? Does one feel a sense of control? Does one need to be vigilant and deferential?).

Basal testosterone's relationship with dictator game decision-making depends on cortisol reactivity to acute stress: A dual-hormone perspective on dominant behavior during resource allocation

The dual-hormone hypothesis proposes that testosterone's relationship with status-seeking behavior is moderated by cortisol. However, research testing this hypothesis has focused on basal cortisol; the potential moderating effect of the acute cortisol response to stress has been largely overlooked. The present research investigated the moderating role of cortisol responses to an acute stressor on basal testosterone's link with dominant, status-relevant decision-making. Also, given the multifaceted nature of the response to acute stress, cardiovascular and affective responses to the stressor were examined as alternative moderators of the testosterone-behavior relationship. Participants (N = 112; 56% female) were exposed to a social-evaluative stressor, and their stress responses were measured. Participants subsequently engaged in a one-shot dictator game, wherein they were asked to split money ($10) with a confederate counterpart. The amount of money participants decided to keep for themselves was treated as a metric of dominant status-seeking behavior. For individuals who demonstrated lower cortisol responses to the stressor, basal testosterone was positively associated with more dominant behavior (i.e., keeping more money for oneself), but for those who showed higher cortisol responses, the testosterone-behavior relationship was suppressed. Moreover, other aspects of the stress response (i.e., cardiovascular and affective responses) did not moderate the relationship between basal testosterone and dictator game behavior. These results provide unique support for the dual-hormone hypothesis using markers of stress-induced cortisol change. The findings also suggest that the antagonistic effects of stress on testosterone's role in motivating status-relevant behavior may be specific to cortisol's role in the acute stress response.

Hormone-Diversity Fit: Collective Testosterone Moderates the Effect of Diversity on Group Performance

Prior research has found inconsistent effects of diversity on group performance. The present research identifies hormonal factors as a critical moderator of the diversity-performance connection. Integrating the diversity, status, and hormone literatures, we predicted that groups collectively low in testosterone, which orients individuals less toward status competitions and more toward cooperation, would excel with greater group diversity. In contrast, groups collectively high in testosterone, which is associated with a heightened status drive, would be derailed by diversity. Analysis of 74 randomly assigned groups engaged in a group decision-making exercise provided support for these hypotheses. The findings suggest that diversity is beneficial for performance, but only if group-level testosterone is low; diversity has a negative effect on performance if group-level testosterone is high. Too much collective testosterone maximizes the pains and minimizes the gains from diversity.

Basal cortisol's relation to testosterone changes may not be driven by social challenges

Multiple studies show a negative correlation between basal cortisol and testosterone changes in the presence of competition and social-evaluative stressors. These negative associations are proposed to be derived from psychological responses to competition and social-evaluative stress. However, we argue that the association between basal cortisol and testosterone change may instead be a statistical consequence of positively associated variables. In this paper, we present a mathematical rationale for this alternative explanation and examples from two studies that are consistent with this alternative explanation. Both studies show that the associations between basal cortisol and testosterone change have covariance patterns consistent with this alternative possibility. We conclude that the often-found positive association between basal cortisol and basal testosterone opens the door for alternative explanations of the basal cortisol-testosterone change association rooted in the patterns of associations between hormones measured over time. We also suggest future research directions and methods for testing alternative explanations.

Does Psychosocial Stress Impact Cognitive Reappraisal? Behavioral and Neural Evidence

Cognitive reappraisal (CR) is regarded as an effective emotion regulation strategy. Acute stress, however, is believed to impair the functioning of prefrontal-based neural systems, which could result in lessened effectiveness of CR under stress. This study tested the behavioral and neurobiological impact of acute stress on CR. While undergoing fMRI, adult participants ( n = 54) passively viewed or used CR to regulate their response to negative and neutral pictures and provided ratings of their negative affect in response to each picture. Half of the participants experienced an fMRI-adapted acute psychosocial stress manipulation similar to the Trier Social Stress Test, and a control group received parallel manipulations without the stressful components. Relative to the control group, the stress group exhibited heightened stress as indexed by self-report, heart rate, and salivary cortisol throughout the scan. Contrary to our hypothesis, we found that reappraisal success was equivalent in the control and stress groups, as was electrodermal response to the pictures. Heart rate deceleration, a physiological response typically evoked by aversive pictures, was blunted in response to negative pictures and heightened in response to neutral pictures in the stress group. In the brain, we found weak evidence of stress-induced increases of reappraisal-related activity in parts of the PFC and left amygdala, but these relationships were statistically fragile. Together, these findings suggest that both the self-reported and neural effects of CR may be robust to at least moderate levels of stress, informing theoretical models of stress effects on cognition and emotion.

Hormonal underpinnings of status conflict: Testosterone and cortisol are related to decisions and satisfaction in the hawk-dove game

A contribution to a special issue on Hormones and Human Competition.Testosterone is theorized to influence status-seeking behaviors such as social dominance and competitive behavior, but supporting evidence is mixed. The present study tested the roles of testosterone and cortisol in the hawk-dove game, a dyadic economic decision-making paradigm in which earnings depend on one's own and the other player's choices. If one person selects the hawk strategy and the other person selects the dove strategy, the player who selected hawk attains a greater financial pay-off (status differentiation). The worst financial outcome occurs when both players choose the hawk strategy (status confrontation). Ninety-eight undergraduate students (42 men) provided saliva samples and played ten rounds of the hawk-dove game with another same-sex participant. In support of the hypothesis that testosterone is related to status concern, individuals higher in basal testosterone made more hawk decisions - decisions that harmed the other player. Acute decreases in cortisol were also associated with more hawk decisions. There was some empirical support for the dual-hormone hypothesis as well: basal testosterone was positively related to satisfaction in the game among low basal-cortisol individuals but not among high basal-cortisol individuals. There were no significant sex differences in these hormonal effects. The present findings align with theories of hormones and status-seeking behavior at the individual level, but they also open up new avenues for research on hormone profiles at the collective level. Our results suggest that the presence of two or more high-testosterone members increases the likelihood of status confrontations over a limited resource that can undermine collective outcomes.

Preliminary evidence that acute stress moderates basal testosterone's association with retaliatory behavior

A contribution to a special issue on Hormones and Human Competition. Testosterone is theorized to increase retaliation after social provocation. However, empirical evidence in support of these theories is mixed. The present research investigated whether acute stress causally suppresses testosterone's association with retaliation. We also explored sex differences in behavioral responses to acute stress. Thirty-nine participants (51.28% male) were randomly assigned to a high- or low-stress condition. Then participants engaged in 20 one-shot rounds of the ultimatum game, which was used to assess retaliatory behavioral responses to unfair treatment. Participants provided two saliva samples to measure testosterone and cortisol concentrations - one sample before the stress manipulation, and the second after the ultimatum game (20minutes post-stressor). Results revealed a positive association between basal testosterone and retaliation in the low-stress condition, but not in the high-stress condition. Further, cortisol concentrations increased in the high- compared to the low-stress condition, and these cortisol changes moderated the association between basal testosterone and retaliation. The associations between basal testosterone and retaliation under varying levels of stress were similar in men and women. However, there was a sex difference in behavioral responses to the stress manipulation that was independent of testosterone. In women, the high-stress condition reduced retaliation compared to the low-stress condition, whereas in men the opposite pattern emerged. Collectively, this study (i) provides preliminary evidence that experimentally manipulated stress blocks basal testosterone's association with retaliation, and (ii) reveals a sex difference in retaliation under varying levels of stress. Discussion focuses on mechanisms, limitations, and the need for follow-up studies with larger sample sizes.

A comparison of salivary testosterone measurement using immunoassays and tandem mass spectrometry

Enzyme immunoassays (EIAs) are widely used to measure salivary testosterone. However, little is known about how accurately different EIAs assess testosterone, partially because estimates across various EIAs differ considerably. We compared testosterone concentrations across EIAs of three commonly used manufacturers (DRG International, Salimetrics, and IBL International) to liquid chromatography tandem mass spectrometry (LC-MS/MS). Relative to EIAs from Salimetrics and IBL International, EIAs supplied by DRG International provided the closest approximation to LC-MS/MS testosterone concentrations, followed closely by EIAs from Salimetrics, and then IBL. Additionally, EIAs tended to inflate estimates of lower testosterone concentrations in women. Examining our results and comparing them to existing data revealed that testosterone EIAs had decreased linear correspondence with LC-MS/MS in comparison to cortisol EIAs. Overall, this paper provides researchers with information to better measure testosterone in their research and more accurately compare testosterone measurements across different methods.

Social network centrality and hormones: The interaction of testosterone and cortisol

In this study we tested whether testosterone and cortisol interacted in predicting social network centrality within a male rugby team. Using social network analysis (SNA), three measures of centrality were investigated: popularity (i.e., the number of incoming ties a participant receives), gregariousness (i.e., the number of ties leaving from a participant and reaching out to others), and betweenness (i.e., the number of times a person lies between two other individuals). In line with the idea that testosterone and cortisol jointly regulate the emergence of social status, we found that individuals with high basal testosterone and low basal cortisol were more popular and more likely to act as connectors among other individuals (i.e., betweenness). The same hormonal profile was not predictive of gregariousness. However, in line with the small literature on the topic, we found that cortisol was inversely correlated with gregariousness. Despite the cross-sectional and correlational nature of our research design, these findings represent the first empirical evidence that testosterone and cortisol interact to predict complex measures of social hierarchy position derived from social network analyses.

Testosterone and cortisol jointly modulate risk-taking

Recent theories propose that testosterone should be positively related to risk-taking, but empirical support is mixed. Building on the dual-hormone hypothesis, the present research tested whether testosterone's role in risk-taking depends on cortisol. Study 1 (N=115) tested this hypothesis in a mixed-sex sample with self and informant reports of risk-taking. Study 2 (N=165) tested this hypothesis in a male-only sample with the Balloon Analog Risk Task, a behavioral measure of risk-taking. Across both studies, there was a positive association between basal testosterone and risk-taking among individuals low in basal cortisol but not individuals high in basal cortisol. This pattern emerged in both males and females and across multiple measures of risk-taking (self reports, informant reports, behavior). These studies provide novel empirical support for the claim that testosterone and cortisol jointly regulate risk-taking. Discussion focuses on putative mechanisms as well as implications for real-world risk-taking behaviors.

A Positive Affective Neuroendocrinology Approach to Reward and Behavioral Dysregulation

Emerging lines of research suggest that both testosterone and maladaptive reward processing can modulate behavioral dysregulation. Yet, to date, no integrative account has been provided that systematically explains neuroendocrine function, dysregulation of reward, and behavioral dysregulation in a unified perspective. This is particularly important given specific neuroendocrine systems are potential mechanisms underlying and giving rise to reward-relevant behaviors. In this review, we propose a forward-thinking approach to study the mechanisms of reward and behavioral dysregulation from a positive affective neuroendocrinology (PANE) perspective. This approach holds that testosterone increases reward processing and motivation, which increase the likelihood of behavioral dysregulation. Additionally, the PANE framework holds that reward processing mediates the effects of testosterone on behavioral dysregulation. We also explore sources of potential sex differences and the roles of age, cortisol, and individual differences within the PANE framework. Finally, we discuss future prospects for research questions and methodology in the emerging field of affective neuroendocrinology.

Testosterone Inhibits Trust but Promotes Reciprocity

The steroid hormone testosterone has been associated with behavior intended to obtain or maintain high social status. Although such behavior is typically characterized as aggressive and competitive, it is clear that high social status is achieved and maintained not only through antisocial behavior but also through prosocial behavior. In the present experiment, we investigated the impact of testosterone administration on trust and reciprocity using a double-blind randomized control design. We found that a single dose of 0.5 mg of testosterone decreased trust but increased generosity when repaying trust. These findings suggest that testosterone may mediate different types of status-seeking behavior. It may increase competitive, potentially aggressive, and antisocial behavior when social challenges and threats (i.e., abuse of trust and betrayal) need to be considered; however, it may promote prosocial behavior in the absence of these threats, when high status and good reputation may be best served by prosocial behavior.

Endogenous testosterone and cortisol jointly influence reactive aggression in women

The dual-hormone hypothesis posits that the effect of testosterone on social behavior is moderated by cortisol. The present study tested this hypothesis with a competitive reactive aggression paradigm in 53 healthy undergraduate women. Salivary cortisol and testosterone were assessed at baseline. Participants were personally insulted and subsequently given the opportunity to retaliate by administering blasts of white noise to the provocateur. Participants were randomly assigned to win or lose the aggressive competition. Basal testosterone positively predicted reactive aggression and state dominance, but only among participants with high concentrations of basal cortisol. The corresponding, reverse pattern was found for state submissiveness. Winners also had higher concentrations of testosterone than losers following the aggressive competition. We discuss the role of heightened reactivity to social provocation as a possible explanation for these effects.

Importance of considering testosterone-cortisol interactions in predicting human aggression and dominance

A novel "field" study recently published in Aggressive Behavior found that individual differences in baseline testosterone concentrations were positively correlated with endorsement of political aggression and that baseline cortisol concentrations were negatively correlated with self-reported aggression among Palestinian boys living in Gaza. Here, we discuss recent evidence indicating that testosterone and cortisol interact to predict competitive, aggressive, and dominant behaviors and urge researchers collecting both hormones to perform and report analyses that formally test for such interaction effects.

Testosterone and Self-Reported Dominance Interact to Influence Human Mating Behavior

In this study, 76 men came into the lab in pairs and engaged in a 7-minute videotaped mate competition for the attention of an attractive female confederate. Pre-competition testosterone (T) levels were positively associated with men’s dominance behaviors and with how much the confederate indicated that she “clicked” with each participant. Dyadic analyses showed that self-reported dominance moderated the effects of T on one’s own dominance behaviors and on opponents' dominance behaviors. Specifically, among men high in self-reported dominance, there was a strong positive association between T and their own dominance behaviors and a strong negative association between T and opponents' dominance behaviors. However, among men low in self-reported dominance, there was no association between T and dominance behaviors. These findings provide novel evidence linking T with evolutionarily adaptive behaviors in humans and suggest that T interacts with people’s explicit dominance motives to regulate behaviors that enhance mating success.

Testosterone and cortisol jointly regulate dominance: evidence for a dual-hormone hypothesis

Traditional theories propose that testosterone should increase dominance and other status-seeking behaviors, but empirical support has been inconsistent. The present research tested the hypothesis that testosterone's effect on dominance depends on cortisol, a glucocorticoid hormone implicated in psychological stress and social avoidance. In the domains of leadership (Study 1, mixed-sex sample) and competition (Study 2, male-only sample), testosterone was positively related to dominance, but only in individuals with low cortisol. In individuals with high cortisol, the relation between testosterone and dominance was blocked (Study 1) or reversed (Study 2). Study 2 further showed that these hormonal effects on dominance were especially likely to occur after social threat (social defeat). The present studies provide the first empirical support for the claim that the neuroendocrine reproductive (HPG) and stress (HPA) axes interact to regulate dominance. Because dominance is related to gaining and maintaining high status positions in social hierarchies, the findings suggest that only when cortisol is low should higher testosterone encourage higher status. When cortisol is high, higher testosterone may actually decrease dominance and in turn motivate lower status.

Neural mechanisms of the testosterone-aggression relation: the role of orbitofrontal cortex

Testosterone plays a role in aggressive behavior, but the mechanisms remain unclear. The present study tested the hypothesis that testosterone influences aggression through the OFC, a region implicated in self-regulation and impulse control. In a decision-making paradigm in which people chose between aggression and monetary reward (the ultimatum game), testosterone was associated with increased aggression following social provocation (rejecting unfair offers). The effect of testosterone on aggression was explained by reduced activity in the medial OFC. The findings suggest that testosterone increases the propensity toward aggression because of reduced activation of the neural circuitry of impulse control and self-regulation.

When are low testosterone levels advantageous? The moderating role of individual versus intergroup competition

Although theory suggests that testosterone should facilitate competitive performance, empirical evidence has been mixed. The present study tested the hypothesis that testosterone's effect on competitive performance depends on whether competition is among individuals (individual competition) or among teams (intergroup competition). Sixty participants (50% women) provided saliva samples and were randomly assigned to complete an analytical reasoning test in individual or intergroup competition. Testosterone was positively related to performance in individual competition, but testosterone was negatively related to performance in intergroup competition. There were no sex differences in performance or in the magnitude of testosterone-performance relationships. These results are consistent with the hypothesis that high testosterone individuals are motivated to gain status (good performance in individual competition), whereas low testosterone individuals are motivated to cooperate with others (good performance in intergroup competition). Theoretical and practical implications are discussed.

The social endocrinology of dominance: basal testosterone predicts cortisol changes and behavior following victory and defeat

Past research suggests that individuals high in basal testosterone are motivated to gain high status. The present research extends previous work by examining endocrinological and behavioral consequences of high and low status as a function of basal testosterone. The outcome of a competition--victory versus defeat--was used as a marker of status. In Study 1, high testosterone men who lost in a dog agility competition rose in cortisol, whereas high testosterone men who won dropped in cortisol. Low testosterone men's cortisol changes did not depend on whether they had won or lost. Study 2 replicated this pattern of cortisol changes in women who participated in an experimental laboratory competition, and Study 2 extended the cortisol findings to behavior. Specifically, high testosterone winners chose to repeat the competitive task, whereas high testosterone losers chose to avoid it. In contrast, low testosterone winners and losers did not differ in their task preferences. These results provide novel evidence in humans that basal testosterone predicts cortisol reactivity and behavior following changes in social status. Implications for the social endocrinology of dominance are discussed.

Bridging human and animal research: a comparative approach to studies of personality and health

This article evaluates a comparative approach to personality and health research. We (1) review evidence showing that personality exists and can be measured in animals, (2) illustrate the benefits of animal studies for human personality research, (3) illustrate the benefits of human studies for animal personality research, and (4) provide guidelines for making cross-species comparisons. We conclude that a comparative approach can provide unique insights into personality psychology, especially into research on personality, immunity, and health.

Testosterone change after losing predicts the decision to compete again

Testosterone (T) levels can fluctuate after wins and losses, but surprisingly, there are no empirical studies in humans that have tested whether these post-competition T changes predict the social behaviors that follow. The present study examined whether changes in T after losing in a competition predicted who wanted to compete again in a second competition. Sixty-four males provided saliva samples immediately before and 15 min after a rigged one-on-one competition. After the second saliva sample, participants chose whether or not to compete again against the same competitor. Winners did not increase in T relative to losers, but pre-competition cortisol, change in cortisol, and pre-competition T were associated with T changes, especially in losers. Importantly, changes in T predicted decisions to compete again in losers. Losers who increased in T were more likely to choose to compete again than losers who decreased in T. T changes were unrelated to decisions to compete again in winners. These findings provide novel data in humans that T changes after a status loss predict subsequent social behavior. Our discussion focuses on the theoretical implications of these findings for the link between short-term T changes and status-related behaviors.

The mismatch effect: when testosterone and status are at odds

Why do some people strive for high status, whereas others actively avoid it? In the present studies, the authors examined the psychological and physiological consequences of a mismatch between baseline testosterone and a person's current level of status. The authors tested this mismatch effect by placing high and low testosterone individuals into high or low status positions using a rigged competition. In Study 1, low testosterone participants reported greater emotional arousal, focused more on their status, and showed worse cognitive functioning in a high status position. High testosterone participants showed this pattern in a low status position. In Study 2, the emotional arousal findings were replicated with heart rate, and the cognitive findings were replicated using a math test. In Study 3, the authors demonstrate that testosterone is a better predictor of behavior than self-report measures of the need for dominance. Discussion focuses on the value of measuring hormones in personality and social psychology.

Contaminated wounds: infection rates with subcutaneous sutures

STUDY OBJECTIVE

To determine whether buried absorbable subcutaneous sutures (BASS) increase the infection rate in irrigated contaminated wounds.

METHODS

This was a randomized, prospective trial in a rat model, with the histologist blinded to treatment group. A single 2-cm dorsal incision was made on each of 30 anesthetized 250-g Sprague-Dawley rats and inoculated with approximately 10(8) organisms of Staphylococcus aureus. After irrigation, 15 wounds were closed with running 4-0 nylon transdermal sutures, and 15 were closed with three interrupted 4-0 coated polyglactin 910 (Vicryl) subcuticular sutures (BASS) and running 4-0 nylon transdermal sutures. On day 7, wounds were scored on a scale of 0 to 3 in six categories: inflammatory infiltrates, fibroplasia and capillary proliferation, necrosis, exudates, giant cells, and edema. The possible range for the cumulative wound score was 0 (no inflammation) to 18 (severe inflammation and infection).

RESULTS

The median total wound score in wounds closed with BASS was 14 (range, 7 to 16); it was 8 (range, 5 to 15) for wounds closed without BASS (P = .0004). The subscores for inflammation, necrosis, exudate, and edema were also significantly higher in wounds closed with BASS.

CONCLUSION

BASS increase the infection rate and the degree of inflammation in contaminated wounds, despite through irrigation.

Enhanced intravenous urography in renal trauma with low-dose dopamine

Intravenous pyelography is the standard first-line investigation for suspected renal trauma. A faint, and/or delayed visualization, or nonvisualization of the damaged renal unit is not uncommon. Low-dose dopamine (3 micrograms/kg/min) increases renal blood flow without deleterious side effects. An experimental rat model was developed to evaluate the effects of low-dose dopamine on intravenous pyelograms in animals with unilateral renal trauma. A consistent and significant improvement in the visualization of the injured kidney was noted in the dopamine-treated animals compared with controls that received equivalent volumes of normal saline.

Intermittent hydronephrosis: a diagnostic challenge

Intermittent hydronephrosis is a difficult condition to diagnose because of the mild degree of dilatation encountered in imaging studies. The condition nevertheless is disabling and attempts to reach a precise diagnosis include diuretic excretory urography, ultrasonography and renal scans. The delayed double-peak pattern seen on 99mtechnetium-diethylenetriaminepentaacetic acid diuretic renography shows how the ureteropelvic junction can become self-obstructing with forced diuresis. All patients who exhibited this sign eventually had frank obstruction and most exhibited an extrinsic component to the obstruction. The recognition of the double-peak pattern may become a useful adjunct in the early diagnosis of intermittent hydronephrosis.