The neural mechanisms by which testosterone acts on interpersonal trust

Testosterone and the Amygdala's Functional Connectivity in Women and Men

The amygdala contains androgen receptors and is involved in various affective and social functions. An interaction between testosterone and the amygdala's functioning is likely. We investigated the amygdala's resting-state functional connectivity (rsFC) network in association with testosterone in 94 healthy young adult women and men (final data available for analysis from 42 women and 39 men). Across the whole sample, testosterone was positively associated with the rsFC between the right amygdala and the right middle occipital gyrus, and it further predicted lower agreeableness scores. Significant sex differences appeared for testosterone and the functional connectivity between the right amygdala and the right superior frontal gyrus (SFG), showing higher testosterone levels with lower connectivity in women. Sex further predicted the openness and agreeableness scores. Our results show that testosterone modulates the rsFC between brain areas involved in affective processing and executive functions. The data indicate that the cognitive control of the amygdala via the frontal cortex is dependent on the testosterone levels in a sex-specific manner. Testosterone seems to express sex-specific patterns (1) in networks processing affect and cognition, and (2) in the frontal down-regulation of the amygdala. The sex-specific coupling between the amygdala and the frontal cortex in interaction with the hormone levels may drive sex-specific differences in a variety of behavioral phenomena that are further associated with psychiatric illnesses that show sex-specific prevalence rates.

A systematic review of psychosocial functioning changes after gender-affirming hormone therapy among transgender people

This systematic review assessed the state and quality of evidence for effects of gender-affirming hormone therapy on psychosocial functioning. Forty-six relevant journal articles (six qualitative, 21 cross-sectional, 19 prospective cohort) were identified. Gender-affirming hormone therapy was consistently found to reduce depressive symptoms and psychological distress. Evidence for quality of life was inconsistent, with some trends suggesting improvements. There was some evidence of affective changes differing for those on masculinizing versus feminizing hormone therapy. Results for self-mastery effects were ambiguous, with some studies suggesting greater anger expression, particularly among those on masculinizing hormone therapy, but no increase in anger intensity. There were some trends toward positive change in interpersonal functioning. Overall, risk of bias was highly variable between studies. Small samples and lack of adjustment for key confounders limited causal inferences. More high-quality evidence for psychosocial effects of gender-affirming hormone therapy is vital for ensuring health equity for transgender people.

Functional connectivity patterns of trait empathy are associated with age

Empathy is the capacity to feel and understand others' mental states. In some individuals, there is an imbalance between the affective and cognitive components of empathy, which can lead to deficits. This study investigated the functional connectivity of the anterior insula (AI) and dorsomedial prefrontal cortex (dmPFC), which play key roles in empathy, in covariation with the affective and cognitive subscales of the Interpersonal Reactivity Index (IRI), as a function of age and sex, as an exploratory analysis. Seed-based functional connectivity analyses were performed on 33 healthy participants that were subdivided according to their age (16 adults and 17 adolescents) and sex (16 women and 17 men). Adolescents reported lower cognitive empathy than adults and men less affective empathy than women. The connectivity of the dmPFC and AI, in covariation with the cognitive and affective subscales of empathy, respectively, differed between adolescents and adults, but was similar in men and women. Adolescents had patterns of negative covariations between the regions of interest and many brain regions associated with the default-mode and salience networks. These findings support that lower self-report levels of empathy in certain individuals could be reflected in the functional connectivity patterns of the dmPFC and AI.

A Systematic Review of the Role of Oxytocin, Cortisol, and Testosterone in Facial Emotional Processing

A topic of interest is the way decoding and interpreting facial emotional expressions can lead to mutual understanding. Facial emotional expression is a basic source of information that guarantees the functioning of other higher cognitive processes (e.g., empathy, cooperativity, prosociality, or decision-making, among others). In this regard, hormones such as oxytocin, cortisol, and/or testosterone have been found to be important in modifying facial emotion processing. In fact, brain structures that participate in facial emotion processing have been shown to be rich in receptors for these hormones. Nonetheless, much of this research has been based on correlational designs. In recent years, a growing number of researchers have tried to carry out controlled laboratory manipulation of these hormones by administering synthetic forms of these hormones. The main objective of this study was to carry out a systematic review of studies that assess whether manipulation of these three hormones effectively promotes significant alterations in facial emotional processing. To carry out this review, PRISMA quality criteria for reviews were followed, using the following digital databases: PsycINFO, PubMed, Dialnet, Psicodoc, Web of Knowledge, and the Cochrane Library, and focusing on manuscripts with a robust research design (e.g., randomized, single- or double-blind, and/or placebo-controlled) to increase the value of this systematic review. An initial identification of 6340 abstracts and retrieval of 910 full texts led to the final inclusion of 101 papers that met all the inclusion criteria. Only about 18% of the manuscripts included reported a direct effect of hormone manipulation. In fact, emotional accuracy seemed to be enhanced after oxytocin increases, but it diminished when cortisol and/or testosterone increased. Nonetheless, when emotional valence and participants' gender were included, hormonal manipulation reached significance (in around 53% of the articles). In fact, these studies offered a heterogeneous pattern in the way these hormones altered speed processing, attention, and memory. This study reinforces the idea that these hormones are important, but not the main modulators of facial emotion processing. As our comprehension of hormonal effects on emotional processing improves, the potential to design good treatments to improve this ability will be greater.

Oxytocin moderates the association between testosterone-cortisol ratio and trustworthiness: A randomized placebo-controlled study

Oxytocin has been proposed to enhance feelings of trust, however, these findings have been difficult to replicate. Environmental or hormonal factors might influence this association. We studied whether oxytocin moderates the association between the testosterone-cortisol ratio, which is associated with risk taking behavior and aggression, and trustworthiness, while controlling for the general level of trust. A randomized double-blind placebo-controlled study with 53 healthy males was performed in which 32IU oxytocin (n = 27) or placebo (n = 26) was administered intranasally. Participants subsequently played the Trust Game in which they were allocated to the role of trustee. In the third phase of the Trust Game, we found a positive association between the testosterone-cortisol-ratio and the proportion of the amount that is returned to the investor (P=<0.01). However, administration of oxytocin reduced reciprocity in those with a high testosterone-cortisol ratio after reciprocity restoration (a significant interaction effect between administration of oxytocin and the testosterone-cortisol ratio in the third phase of the Trust Game, P = 0.015). The third phase of the Trust Game represents the restoration of reciprocity and trustworthiness, after this is violated in the second phase. Therefore, our data suggest that oxytocin might hinder the restoration of trustworthiness and diminish risk-taking behavior when trust is violated, especially in those who are hormonally prone to risk-taking behavior by a high testosterone-cortisol ratio.

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Oxytocin (32IU) was administered intranasally to healthy young males in a double-blind placebo-controlled study.

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Testosterone-cortisol ratio was positively associated with trustworthiness during the Trust Game.

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Oxytocin significantly attenuated the association between testosterone-cortisol ratio and trustworthiness.

Effects of testosterone administration on fMRI responses to executive function, aggressive behavior, and emotion processing tasks during severe exercise- and diet-induced energy deficit

BACKGROUND

Clinical administration of testosterone is widely used due to a variety of claimed physical and cognitive benefits. Testosterone administration is associated with enhanced brain and cognitive function, as well as mood, in energy-balanced males, although such relationships are controversial. However, the effects of testosterone administration on the brains of energy-deficient males, whose testosterone concentrations are likely to be well below normal, have not been investigated.

METHODS

This study collected functional magnetic resonance imaging (fMRI) data from 50 non-obese young men before (PRE) and shortly after (POST) 28 days of severe exercise-and-diet-induced energy deficit during which testosterone (200 mg testosterone enanthate per week in sesame oil, TEST) or placebo (sesame seed oil only, PLA) were administered. Scans were also collected after a post-energy-deficit weight regain period (REC). Participants completed five fMRI tasks that assessed aspects of: 1) executive function (Attention Network Task or ANT; Multi-Source Interference Task or MSIT; AXE Continuous Processing Task or AXCPT); 2) aggressive behavior (Provoked Aggression Task or AGG); and 3) latent emotion processing (Emotional Face Processing or EMO).

RESULTS

Changes over time in task-related fMRI activation in a priori defined task-critical brain regions during performance of 2 out of 5 tasks were significantly different between TEST and PLA, with TEST showing greater levels of activation during ANT in the right anterior cingulate gyrus at POST and during MSIT in several brain regions at REC. Changes over time in objective task performance were not statistically significant; testosterone-treated volunteers had greater self-reported anger during AGG at POST.

CONCLUSIONS

Testosterone administration can alter some aspects of brain function during severe energy deficit and increase levels of anger.

Navigating Motivation: A Semantic and Subjective Atlas of 7 Motives

Research from psychology, neurobiology and behavioral economics indicates that a binary view of motivation, based on approach and avoidance, may be too reductive. Instead, a literature review suggests that at least seven distinct motives are likely to affect human decisions: "consumption/resource seeking," "care," "affiliation," "achievement," "status-power," "threat approach" (or anger), and "threat avoidance" (or fear). To explore the conceptual distinctness and relatedness of these motives, we conducted a semantic categorization task. Here, participants were to assign provided words to one of the motives. By applying principal component analysis to the categorization assignments we represent the semantic inter-relations of these motives on a two-dimensional space, a "semantic atlas." This atlas suggests that, while care and affiliation are conceptually close, affiliation is closer to threat avoidance (or fear); opposite to these motives we find achievement, consumption and power, with the latter lying closer to threat approach (or anger). In a second study, we asked participants to rate how well the motive-specific words obtained in the first study described their currently experienced feelings. We find that semantically close motives are also more likely to be experienced together, that is, we replicate most of the semantic relations in the "subjective atlas." We discuss our findings in comparison to other multi-dimensional models of motivation, which show clear similarities. In addition to these motivational atlases, we provide a database of motive-specific words, together with the valence and arousal scores. These can be used for future research on the influence of motives on decision making.

Effect of Modulating DLPFC Activity on Antisocial and Prosocial Behavior: Evidence From a tDCS Study

Antisocial behavior and prosocial behavior in the condition of inequality have long been observed in daily life. Understanding the neurological mechanisms and brain regions associated with antisocial and prosocial behavior and the development of new interventions are important for reducing violence and inequality. Fortunately, neurocognitive research and brain imaging research have found a correlation between antisocial or prosocial behavior and the prefrontal cortex. Recent brain stimulation research adopting transcranial direct current stimulation or transcranial magnetic stimulation has shown a causal relationship between brain regions and behaviors, but the findings are mixed. In the present study, we aimed to study whether stimulation of the DLPFC can change participants’ antisocial and prosocial behavior in the condition of inequality. We integrated antisocial and prosocial behavior in a unified paradigm. Based on this paradigm, we discussed costly and cost-free antisocial and prosocial behavior. In addition, we also measured participants’ disadvantageous and advantageous inequality aversion. The current study revealed an asymmetric effect of bilateral stimulation over the DLPFC on costly antisocial behavior, while such an effect of antisocial behavior without cost and prosocial behavior with and without cost were not observed. Moreover, costly antisocial behavior exhibited by men increased after receiving right anodal/left cathodal stimulation and decreased after receiving right cathodal anodal/left anodal stimulation compared with the behavior observed under sham stimulation. However, subjects’ inequality aversion was not influenced by tDCS.

Methylation of oxytocin related genes and early life trauma together shape the N170 response to human faces

Childhood trauma fundamentally shapes social cognition and basic processing of social cues, which frequently cascade into adverse behavioral outcomes. Recent studies indicate that epigenetic changes in oxytocin functioning might contribute to these long-term effects, although a deeper understanding of the underlying mechanisms is still lacking. The electroencephalographic N170 response to faces might capture a neural response at the core of these interactive effects of oxytocin gene methylation and childhood adversity, given that this response is considered to reflect fundamental face processing, to be susceptible to oxytocin administration and also to be a biomarker of various psychiatric disorders. We assessed the N170 response to neutral faces in relation to participant's (81, women) recalled childhood trauma, methylation of their oxytocin structural (OXTg) and oxytocin receptor (OXTRg) genes, and endogenous levels of cortisol and testosterone. Additionally, we investigated the interactive effect of OXTg methylation and CTQ across three face sets of varying maturity. Methylation of OXTg relates to a weakened N170 response towards adults, children and infants. Moreover, methylation of both OXTRg and OXTg shaped the directionality of adversity effects, predicting a weakened N170 response in those with high methylation and hyper-vigilance with participants with low methylation. Our results are the first to relate OXT(R)g methylation to the N170 response. They shed light on biological processes linking childhood adversity and epigenetic marks to altered behavior and potentially psychopathologies.

Testosterone administration in human social neuroendocrinology: Past, present, and future

Over the past 20 years, social neuroendocrinology researchers have developed pharmacological challenge paradigms to assess the extent to which testosterone plays a causal role in human psychological and behavioural processes. The current paper provides a brief summary of this research and offers recommendations for future research examining the neuroendocrine mechanisms underlying human behaviour.

Testosterone and Fathers’ Parenting Unraveled: Links with the Quantity and Quality of Father-Child Interactions

Objective

Individual differences in quality of father involvement in caregiving might in part be explained by fathers’ testosterone (T) levels. We examined the links between fathers’ (n = 32) salivary T levels, amount of time spent with their child (12–30 months of age), type of father-child interaction, and fathers’ sensitivity.

Methods

During two home visits, video observations of father-child interactions were conducted to measure fathers’ sensitivity during a challenging and harmonious interaction. Fathers’ saliva was collected several times throughout the day on a working day and on the home visit days, including right before and after each father-child interaction.

Results

Fathers’ T secretion throughout the day was lower on home visit days (i.e., days with a higher amount of time spent with their child) than on a working day. For both challenging and harmonious father-child interactions, mean T levels did not differ before and after father-child interactions. However, individual changes in fathers’ T levels during the father-child interactions did predict fathers’ sensitivity. Specifically, the more T increased during the challenging interaction, or decreased during the harmonious interaction, the more sensitive the father was during that interaction as well as during a subsequent interaction.

Conclusions

Parenting quality is most optimal when fathers’ T system reacts in the expected direction given the context of the father-child interaction, i.e., a T decrease during a harmonious interaction and a T increase during a challenging interaction. Our study underscores the importance of examining the interplay between biology, behavior, and caregiving context in fathers’ parenting.

Trust, Sexual Trust, and Sexual Health: An Interrogative Review

Trust is experienced almost constantly in all forms of social and interpersonal relationships, including sexual relationships, and may contribute both directly and indirectly to sexual health. The purpose of this review is to link three aspects of trust to sexual health: (1) the role of trust in sexual relationships; (2) the role of trust in sexually transmitted infection (STI) prevention, particularly condom use; and (3) the relevance of trust in sexual relationships outside of the traditional model of monogamy. The review ends with consideration of perspectives that could guide new research toward understanding the enigmas of trust in partnered sexual relations in the context of sexual and public health.

Psychoanalysis and Affective Neuroscience. The Motivational/Emotional System of Aggression in Human Relations

This article highlights the evolutionary biological epistemology in Freud psychoanalytic theory. The concepts of aggressive and sexual drives are cornerstones of the psychoanalytic epistemological system, concerning the motivational/emotional roots of mental functioning. These biological roots of mental functioning, especially with regard to aggressive drive, have gradually faded away from psychoanalytic epistemology, as we show in this article. Currently, however, Neurosciences, and in particular Affective Neuroscience (Panksepp, 1998), can help us to have a better understanding of the biological roots of human mental functioning. The motivational/emotional systems studied by Affective Neuroscience can give a new epistemological foundation to the aggressive drive concept in psychoanalytic theory. Over the course of human evolution, motivational/emotional systems have played a role in social relationships and also in mental functioning. In this regard, among the various types of aggression (ANGER in Panksepp taxonomy 1998) that we consider in our article, inter-male aggression, also named Dominance motivational/emotional system, is that which regulates social interactions between sexually matured adults. This type of aggression acts in complementary connection with FEAR motivational/emotional system that regulate submissive behavior and social defeat, and the latter one is of the more important stressors. The interaction between aggression and FEAR motivational/emotional systems gives rise to agonistic behavior or dominance/submission motivational/emotional system, as we propose in our article. There is now a large literature that identifies in the dynamic of Competitive behavior, which is one of the main factors of mental illness. When social interactions activate the competitive behavior, the subject can perceive himself as "destined to victory" or "destined to defeat," activating either behaviors or emotions connected to the Involuntary Defeat Strategy or Involuntary Dominant Strategy (Sloman, 2002), which we can find in many types of mental disorders, for example, mood disorders or anxiety disorders.

Doubled-Edged Swords in the Biology of Conflict

Considerable advances have been made in understanding the biological roots of conflict, and such understanding requires a multidisciplinary approach, recognizing the relevance of neurobiological, endocrine, genetic, developmental, and evolutionary perspectives. With these insights comes the first hints of biological interventions that may mitigate violence. However, such interventions are typically double-edged swords, with the potential to foster conflict rather than lessen it. This review constitutes a cautionary note of being careful of what one wishes for.

Effects of testosterone administration on threat and escape anticipation in the orbitofrontal cortex

Recent evidence suggests that the steroid hormone testosterone can decrease the functional coupling between orbitofrontal cortex (OFC) and amygdala. Theoretically this decoupling has been linked to a testosterone-driven increase of goal-directed behaviour in case of threat, but this has never been studied directly. Therefore, we placed twenty-two women in dynamically changing situations of escapable and inescapable threat after a within-subject placebo controlled testosterone administration. Using functional magnetic resonance imaging (fMRI) we provide evidence that testosterone activates the left lateral OFC (LOFC) in preparation of active goal-directed escape and decouples this OFC area from a subcortical threat system including the central-medial amygdala, hypothalamus and periaqueductal gray. This LOFC decoupling was specific to threatening situations, a point that was further emphasized by an absence of such decoupling in a second experiment focused on resting-state connectivity. These results not only confirm that testosterone administration decouples the LOFC from the subcortical threat system, but also show that this is specifically the case in response to acute threat, and ultimately leads to an increase in LOFC activity when the participant prepares a goal-directed action to escape. Together these results for the first time provide a detailed understanding of functional brain alterations induced by testosterone under threat conditions, and corroborate and extend the view that testosterone prepares the brain for goal-directed action in case of threat.

The neural correlates of trustworthiness evaluations of faces and brands: Implications for behavioral and consumer neuroscience

When we buy a product of a brand, we trust the brand to provide good quality and reliability. Therefore, trust plays a major role in consumer behavior. It is unclear, however, how trust in brands is processed in the brain and whether it is processed differently from interpersonal trust. In this study, we used fMRI to investigate the neural correlates of interpersonal and brand trust by comparing the brain activation patterns during explicit trustworthiness judgments of faces and brands. Our results showed that while there were several brain areas known to be linked to trustworthiness evaluations, such as the amygdalae, more active in trustworthiness judgments when compared to a control task (familiarity judgment) for faces, no such difference was found for brands. Complementary ROI analysis revealed that the activation of both amygdalae was strongest for faces in the trustworthiness judgments. The direct comparison of the brain activation patterns during the trustworthiness evaluations between faces and brands in this analysis showed that trustworthiness judgments of faces activated the orbitofrontal cortex, another region that was previously linked to interpersonal trust, more strongly than trustworthiness judgments of brands. Further, trustworthiness ratings of faces, but not brands, correlated with activation in the orbitofrontal cortex. Our results indicate that the amygdalae, as well as the orbitofrontal cortex, play a prominent role in interpersonal trust (faces), but not in trust for brands. It is possible that this difference is due to brands being processed as cultural objects rather than as having human-like personality characteristics.

Evolutionary perspective on sex differences in the expression of neurological diseases

Sex-specific brain and cognitive deficits emerge with malnutrition, some infectious and neurodegenerative diseases, and often with prenatal or postnatal toxin exposure. These deficits are described in disparate literatures and are generally not linked to one another. Sexual selection may provide a unifying framework that integrates our understanding of these deficits and provides direction for future studies of sex-specific vulnerabilities. Sexually selected traits are those that have evolved to facilitate competition for reproductive resources or that influence mate choices, and are often larger and more complex than other traits. Critically, malnutrition, disease, chronic social stress, and exposure to man-made toxins compromise the development and expression of sexually selected traits more strongly than that of other traits. The fundamental mechanism underlying vulnerability might be the efficiency of mitochondrial energy capture and control of oxidative stress that in turn links these traits to current advances in neuroenergetics, stress endocrinology, and toxicology. The key idea is that the elaboration of these cognitive abilities, with more underlying gray matter or more extensive inter-modular white matter connections, makes them particularly sensitive to disruptions in mitochondrial functioning and oxidative stress. A framework of human sexually selected cognitive abilities and underlying brain systems is proposed and used to organize what is currently known about sex-specific vulnerabilities.

The Neural Basis of and a Common Neural Circuitry in Different Types of Pro-social Behavior

Pro-social behaviors are voluntary behaviors that benefit other people or society as a whole, such as charitable donations, cooperation, trust, altruistic punishment, and fairness. These behaviors have been widely described through non self-interest decision-making in behavioral experimental studies and are thought to be increased by social preference motives. Importantly, recent studies using a combination of neuroimaging and brain stimulation, designed to reveal the neural mechanisms of pro-social behaviors, have found that a wide range of brain areas, specifically the prefrontal cortex, anterior insula, anterior cingulate cortex, and amygdala, are correlated or causally related with pro-social behaviors. In this review, we summarize the research on the neural basis of various kinds of pro-social behaviors and describe a common shared neural circuitry of these pro-social behaviors. We introduce several general ways in which experimental economics and neuroscience can be combined to develop important contributions to understanding social decision-making and pro-social behaviors. Future research should attempt to explore the neural circuitry between the frontal lobes and deeper brain areas.

Testosterone, Cortisol and Financial Risk-Taking

Both testosterone and cortisol have major actions on financial decision-making closely related to their primary biological functions, reproductive success and response to stress, respectively. Financial risk-taking represents a particular example of strategic decisions made in the context of choice under conditions of uncertainty. Such decisions have multiple components, and this article considers how much we know of how either hormone affects risk-appetite, reward value, information processing and estimation of the costs and benefits of potential success or failure, both personal and social. It also considers how far we can map these actions on neural mechanisms underlying risk appetite and decision-making, with particular reference to areas of the brain concerned in either cognitive or emotional functions.

High voice pitch mitigates the aversiveness of antisocial cues in men's speech

Speech contains both explicit social information in semantic content and implicit cues to social behaviour and mate quality in voice pitch. Voice pitch has been demonstrated to have pervasive effects on social perceptions, but few studies have examined these perceptions in the context of meaningful speech. Here, we examined whether male voice pitch interacted with socially relevant cues in speech to influence listeners' perceptions of trustworthiness and attractiveness. We artificially manipulated men's voices to be higher and lower in pitch when speaking words that were either prosocial or antisocial in nature. In Study 1, we found that listeners perceived lower-pitched voices as more trustworthy and attractive in the context of prosocial words than in the context of antisocial words. In Study 2, we found evidence that suggests this effect was driven by stronger preferences for higher-pitched voices in the context of antisocial cues, as voice pitch preferences were not significantly different in the context of prosocial cues. These findings suggest that higher male voice pitch may ameliorate the negative effects of antisocial speech content and that listeners may be particularly avoidant of those who express multiple cues to antisociality across modalities.

Older adults' neural activation in the reward circuit is sensitive to face trustworthiness

We examined older adult (OA) and younger adult (YA) neural sensitivity to face trustworthiness in reward circuit regions, previously found to respond to trustworthiness in YA. Interactions of face trustworthiness with age revealed effects exclusive to OA in the amygdala and caudate, and an effect that was not moderated by age in the dorsal anterior cingulate cortex (dACC). OA, but not YA, showed a nonlinear amygdala response to face trustworthiness, with significantly stronger activation response to high than to medium trustworthy faces, and no difference between low and medium or high. This may explain why an earlier study investigating OA amygdala activation to trustworthiness failed to find a significant effect, since only the linear low versus high trustworthiness difference was assessed. OA, but not YA, also showed significantly stronger activation to high than to low trustworthy faces in the right caudate, indicating a positive linear effect, consistent with previous YA research, as well as significantly stronger activation to high than to medium but not low trustworthy faces in the left caudate, indicating a nonlinear effect. Activation in dACC across both age groups showed a positive linear effect consistent with previous YA research. Finally, OA rated the faces as more trustworthy than did YA across all levels of trustworthiness. Future research should examine whether the null effects for YA were due to our inclusion of older faces. Research also should investigate possible implications of our findings for more ecologically valid OA responses to people who vary in facial trustworthiness.

Implicit and Explicit Motivational Tendencies to Faces Varying in Trustworthiness and Dominance in Men

Motivational tendencies to happy and angry faces are well-established, e.g., in the form of aggression. Approach-avoidance reactions are not only elicited by emotional expressions, but also linked to the evaluation of stable, social characteristics of faces. Grounded in the two fundamental dimensions of face-based evaluations proposed by Oosterhof and Todorov (2008), the current study tested whether emotionally neutral faces varying in trustworthiness and dominance potentiate approach-avoidance in 50 healthy male participants. Given that evaluations of social traits are influenced by testosterone, we further tested for associations of approach-avoidance tendencies with endogenous and prenatal indicators of testosterone. Computer-generated faces signaling high and low trustworthiness and dominance were used to elicit motivational reactions in three approach-avoidance tasks, i.e., one implicit and one explicit joystick-based paradigm, and an additional rating task. When participants rated their behavioral tendencies, highly trustworthy faces evoked approach, and highly dominant faces evoked avoidance. This pattern, however, did not translate to faster initiation times of corresponding approach-avoidance movements. Instead, the joystick tasks revealed general effects, such as faster reactions to faces signaling high trustworthiness or high dominance. These findings partially support the framework of Oosterhof and Todorov (2008) in guiding approach-avoidance decisions, but not behavioral tendencies. Contrary to our expectations, neither endogenous nor prenatal indicators of testosterone were associated with motivational tendencies. Future studies should investigate the contexts in which testosterone influences social motivation.

Social evaluative threat with verbal performance feedback alters neuroendocrine response to stress

Laboratory stress tasks such as the Trier Social Stress Test (TSST) have provided a key piece to the puzzle for how psychosocial stress impacts the hypothalamic-pituitary-adrenal axis, other stress-responsive biomarkers, and ultimately wellbeing. These tasks are thought to work through biopsychosocial processes, specifically social evaluative threat and the uncontrollability heighten situational demands. The present study integrated an experimental modification to the design of the TSST to probe whether additional social evaluative threat, via negative verbal feedback about speech performance, can further alter stress reactivity in 63 men and women. This TSST study confirmed previous findings related to stress reactivity and stress recovery but extended this literature in several ways. First, we showed that additional social evaluative threat components, mid-task following the speech portion of the TSST, were still capable of enhancing the psychosocial stressor. Second, we considered stress-reactive hormones beyond cortisol to include dehydroepiandrosterone (DHEA) and testosterone, and found these hormones were also stress-responsive, and their release was coupled with one another. Third, we explored whether gain- and loss-framing incentive instructions, meant to influence performance motivation by enhancing the personal relevance of task performance, impacted hormonal reactivity. Results showed that each hormone was stress reactive and further had different responses to the modified TSST compared to the original TSST. Beyond the utility of showing how the TSST can be modified with heightened social evaluative threat and incentive-framing instructions, this study informs about how these three stress-responsive hormones have differential responses to the demands of a challenge and a stressor.

Functional significance of men's testosterone reactivity to social stimuli

Rapid testosterone fluctuations in response to social stimuli are observed across a wide range of species, and the highly conserved nature of these fluctuations suggests an adaptive function. This paper reviews the current literature on testosterone reactivity, primarily in human males, and illustrates how life-history theory provides an adequate theoretical framework to interpret findings. The review is structured around supporting evidence suggesting that situations implicated in mating effort either directly (e.g., interactions with a mate) or indirectly (e.g., intrasexual competition) are generally associated with a brief elevation of testosterone, while situations implicated in parenting effort (e.g., nurturant interactions with offspring) are generally associated with a decline in testosterone. Further, we discuss how these fluctuations in testosterone have been linked to future behaviors, and how situational, motivational, and physiological variables moderate the interplay between social stimuli, testosterone reactivity, and behavior. Supporting the notion that testosterone can play a causal role in modulating behavior in response to social stimuli, we also summarize recent single administration studies examining the effects of testosterone on physiology, neurobiology, and behavior. A conceptual model provides links between supported findings, and hypothesized pathways requiring future testing.

Single-Dose Testosterone Administration Impairs Cognitive Reflection in Men

In nonhumans, the sex steroid testosterone regulates reproductive behaviors such as fighting between males and mating. In humans, correlational studies have linked testosterone with aggression and disorders associated with poor impulse control, but the neuropsychological processes at work are poorly understood. Building on a dual-process framework, we propose a mechanism underlying testosterone’s behavioral effects in humans: reduction in cognitive reflection. In the largest study of behavioral effects of testosterone administration to date, 243 men received either testosterone or placebo and took the Cognitive Reflection Test (CRT), which estimates the capacity to override incorrect intuitive judgments with deliberate correct responses. Testosterone administration reduced CRT scores. The effect remained after we controlled for age, mood, math skills, whether participants believed they had received the placebo or testosterone, and the effects of 14 additional hormones, and it held for each of the CRT questions in isolation. Our findings suggest a mechanism underlying testosterone’s diverse effects on humans’ judgments and decision making and provide novel, clear, and testable predictions.

On the Control of Social Approach-Avoidance Behavior: Neural and Endocrine Mechanisms

The ability to control our automatic action tendencies is crucial for adequate social interactions. Emotional events trigger automatic approach and avoidance tendencies. Although these actions may be generally adaptive, the capacity to override these emotional reactions may be key to flexible behavior during social interaction. The present chapter provides a review of the neuroendocrine mechanisms underlying this ability and their relation to social psychopathologies. Aberrant social behavior, such as observed in social anxiety or psychopathy, is marked by abnormalities in approach-avoidance tendencies and the ability to control them. Key neural regions involved in the regulation of approach-avoidance behavior are the amygdala, widely implicated in automatic emotional processing, and the anterior prefrontal cortex, which exerts control over the amygdala. Hormones, especially testosterone and cortisol, have been shown to affect approach-avoidance behavior and the associated neural mechanisms. The present chapter also discusses ways to directly influence social approach and avoidance behavior and will end with a research agenda to further advance this important research field. Control over approach-avoidance tendencies may serve as an exemplar of emotional action regulation and might have a great value in understanding the underlying mechanisms of the development of affective disorders.

The Role of the Amygdala in Facial Trustworthiness Processing: A Systematic Review and Meta-Analyses of fMRI Studies

Background

Faces play a key role in signaling social cues such as signals of trustworthiness. Although several studies identify the amygdala as a core brain region in social cognition, quantitative approaches evaluating its role are scarce.

Objectives

This review aimed to assess the role of the amygdala in the processing of facial trustworthiness, by analyzing its amplitude BOLD response polarity to untrustworthy versus trustworthy facial signals under fMRI tasks through a Meta-analysis of effect sizes (MA). Activation Likelihood Estimation (ALE) analyses were also conducted.

Data sources

Articles were retrieved from MEDLINE, ScienceDirect and Web-of-Science in January 2016. Following the PRISMA statement guidelines, a systematic review of original research articles in English language using the search string “(face OR facial) AND (trustworthiness OR trustworthy OR untrustworthy OR trustee) AND fMRI” was conducted.

Study selection and data extraction

The MA concerned amygdala responses to facial trustworthiness for the contrast Untrustworthy vs. trustworthy faces, and included whole-brain and ROI studies. To prevent potential bias, results were considered even when at the single study level they did not survive correction for multiple comparisons or provided non-significant results. ALE considered whole-brain studies, using the same methodology to prevent bias. A summary of the methodological options (design and analysis) described in the articles was finally used to get further insight into the characteristics of the studies and to perform a subgroup analysis. Data were extracted by two authors and checked independently.

Data synthesis

Twenty fMRI studies were considered for systematic review. An MA of effect sizes with 11 articles (12 studies) showed high heterogeneity between studies [Q(11) = 265.68, p < .0001; I² = 95.86%, 94.20% to 97.05%, with 95% confidence interval, CI]. Random effects analysis [RE(183) = 0.851, .422 to .969, 95% CI] supported the evidence that the (right) amygdala responds preferentially to untrustworthy faces. Moreover, two ALE analyses performed with 6 articles (7 studies) identified the amygdala, insula and medial dorsal nuclei of thalamus as structures with negative correlation with trustworthiness. Six articles/studies showed that posterior cingulate and medial frontal gyrus present positive correlations with increasing facial trustworthiness levels. Significant effects considering subgroup analysis based on methodological criteria were found for experiments using spatial smoothing, categorization of trustworthiness in 2 or 3 categories and paradigms which involve both explicit and implicit tasks.

Limitations

Significant heterogeneity between studies was found in MA, which might have arisen from inclusion of studies with smaller sample sizes and differences in methodological options. Studies using ROI analysis / small volume correction methods were more often devoted specifically to the amygdala region, with some results reporting uncorrected p-values based on mainly clinical a priori evidence of amygdala involvement in these processes. Nevertheless, we did not find significant evidence for publication bias.

Conclusions and implications of key findings

Our results support the role of amygdala in facial trustworthiness judgment, emphasizing its predominant role during processing of negative social signals in (untrustworthy) faces. This systematic review suggests that little consistency exists among studies’ methodology, and that larger sample sizes should be preferred.

The endocrinology of human caregiving and its intergenerational transmission

Variation in the quality of parental care has a tremendous impact on a child's social–emotional development. Research investigating the predictors of this variability in human caregiving behavior has mostly focused on learning mechanisms. Evidence is currently accumulating for the complementary underlying role of steroid hormones and neuropeptides. An overview is provided of the hormones and neuropeptides relevant for human caregiving behavior. Then the developmental factors are described that stimulate variability in sensitivity to these hormones and neuropeptides, which may result in variability in the behavioral repertoire of caregiving. The role of genetic variation in neuropeptide and steroid receptors, the role of testosterone and oxytocin during fetal development and parturition, and the impact of experienced caregiving in childhood on functioning of the neuroendocrine stress and oxytocin system are discussed. Besides providing a heuristic framework for further research on the ontogenetic development of human caregiving, a neuroendocrine model is also presented for the intergenerational transmission of caregiving practices. Insight into the underlying biological mechanisms that bring about maladaptive caregiving behavior, such as neglect and insensitive parenting, will hopefully result in more efficient approaches to reduce the high prevalence of such behavior and to minimize the impact on those affected.

Testosterone reduces functional connectivity during the 'Reading the Mind in the Eyes' Test

Women on average outperform men in cognitive-empathic abilities, such as the capacity to infer motives from the bodily cues of others, which is vital for effective social interaction. The steroid hormone testosterone is thought to play a role in this sexual dimorphism. Strikingly, a previous study shows that a single administration of testosterone in women impairs performance on the 'Reading the Mind in Eyes' Test (RMET), a task in which emotions have to be inferred from the eye-region of a face. This effect was mediated by the 2D:4D ratio, the ratio between the length of the index and ring finger, a proxy for fetal testosterone. Research in typical individuals, in individuals with autism spectrum conditions (ASC), and in individuals with brain lesions has established that performance on the RMET depends on the left inferior frontal gyrus (IFG). Using functional magnetic resonance imaging (fMRI), we found that a single administration of testosterone in 16 young women significantly altered connectivity of the left IFG with the anterior cingulate cortex (ACC) and the supplementary motor area (SMA) during RMET performance, independent of 2D:4D ratio. This IFG-ACC-SMA network underlies the integration and selection of sensory information, and for action preparation during cognitive empathic behavior. Our findings thus reveal a neural mechanism by which testosterone can impair emotion-recognition ability, and may link to the symptomatology of ASC, in which the same neural network is implicated.

A quantitative and qualitative review of the effects of testosterone on the function and structure of the human social-emotional brain

Social and affective research in humans is increasingly using functional and structural neuroimaging techniques to aid the understanding of how hormones, such as testosterone, modulate a wide range of psychological processes. We conducted a meta-analysis of functional magnetic resonance imaging (fMRI) studies of testosterone administration, and of fMRI studies that measured endogenous levels of the hormone, in relation to social and affective stimuli. Furthermore, we conducted a review of structural MRI i.e. voxel based morphometry (VBM) studies which considered brain volume in relation to testosterone levels in adults and in children. In the included testosterone administration fMRI studies, which consisted of female samples only, bilateral amygdala/parahippocampal regions as well as the right caudate were significantly activated by social-affective stimuli in the testosterone condition. In the studies considering endogenous levels of testosterone, stimuli-invoked activations relating to testosterone levels were noted in the bilateral amygdala/parahippocampal regions and the brainstem. When the endogenous testosterone studies were split by sex, the significant activation of the brain stem was seen in the female samples only. Significant stimuli-invoked deactivations relating to endogenous testosterone levels were also seen in the right and left amygdala/parahippocampal regions studies. The findings of the VBM studies were less consistent. In adults larger volumes in the limbic and temporal regions were associated with higher endogenous testosterone. In children, boys showed a positive correlation between testosterone and brain volume in many regions, including the amygdala, as well as global grey matter volume, while girls showed a neutral or negative association between testosterone levels and many brain volumes. In conclusion, amygdalar and parahippocampal regions appear to be key target regions for the acute actions of testosterone in response to social and affective stimuli, while neurodevelopmentally the volumes of a broader network of brain structures are associated with testosterone levels in a sexually dimorphic manner.

A testosterone-related structural brain phenotype predicts aggressive behavior from childhood to adulthood

Structural covariance, the examination of anatomic correlations between brain regions, has emerged recently as a valid and useful measure of developmental brain changes. Yet the exact biological processes leading to changes in covariance, and the relation between such covariance and behavior, remain largely unexplored. The steroid hormone testosterone represents a compelling mechanism through which this structural covariance may be developmentally regulated in humans. Although steroid hormone receptors can be found throughout the central nervous system, the amygdala represents a key target for testosterone-specific effects, given its high density of androgen receptors. In addition, testosterone has been found to impact cortical thickness (CTh) across the whole brain, suggesting that it may also regulate the structural relationship, or covariance, between the amygdala and CTh. Here, we examined testosterone-related covariance between amygdala volumes and whole-brain CTh, as well as its relationship to aggression levels, in a longitudinal sample of children, adolescents, and young adults 6-22 years old. We found: (1) testosterone-specific modulation of the covariance between the amygdala and medial prefrontal cortex (mPFC); (2) a significant relationship between amygdala-mPFC covariance and levels of aggression; and (3) mediation effects of amygdala-mPFC covariance on the relationship between testosterone and aggression. These effects were independent of sex, age, pubertal stage, estradiol levels and anxious-depressed symptoms. These findings are consistent with prior evidence that testosterone targets the neural circuits regulating affect and impulse regulation, and show, for the first time in humans, how androgen-dependent organizational effects may regulate a very specific, aggression-related structural brain phenotype from childhood to young adulthood.

Changes in spatial cognition and brain activity after a single dose of testosterone in healthy women

Studies have consistently shown that males perform better than females on several spatial tasks. Animal and human literature suggests that sex hormones have an important role in both establishing and maintaining this difference. The aim of the present study was to examine the effects of exogenous testosterone on spatial cognition and brain activity in healthy women. A cross-sectional, double-blind, randomized, placebo-controlled study was performed in 42 healthy young women who either received one dose of 0.5mg sublingual testosterone or placebo. They then learned a virtual environment and performed navigation tasks during functional magnetic resonance imaging (fMRI). Subsequently, their knowledge of the virtual environment, self-reported navigation strategy, and mental rotation abilities were measured. The testosterone group had improved representations of the directions within the environment and performed significantly better on the mental rotation task compared to the placebo group, but navigation success and navigation strategy were similar in the two groups. Nevertheless, the testosterone group had significantly increased activity within the medial temporal lobe during successful navigation compared to the placebo group, and a positive correlation between testosterone load and medial temporal lobe activity was found. Fetal testosterone levels, measured as second-to-fourth digit length ratio, interacted significantly with parahippocampal activity and tended towards giving higher mental rotation task scores. These results demonstrated that testosterone had a limited effect pertaining specifically to spatial cognition involving 3D-visualization in healthy women, while complex behaviors such as navigation, relying more on learned strategies, were not altered despite increased neuronal activity in relevant brain regions.

A Pilot Study on Tamoxifen Sexual Side Effects and Hand Preference in Male Breast Cancer

Recent clinical and imaging studies suggest that sex hormones modulate sexuality according to a psychophysiologic process of lateralization of the brain, with androgens playing a greater role in sexual functioning of left hemibrain/right handedness and estrogens possibly for right hemibrain/left handedness. Based on this perspective, the current study attempted to specify the relationship between hand preference, estrogens, and sexual function in subjects with male breast cancer, taking into account the sexual side effects of tamoxifen as the agent for inhibiting estrogen action. Twenty-eight Romanian men-17 right-handed and 11 left-handed-undergoing treatment with tamoxifen for male breast cancer participated in this study. These men were assessed both prior to and during tamoxifen treatment using the International Index of Erectile Function, a standardized instrument used for the evaluation of various aspects of sexual functioning, including erectile function (EF), orgasmic function (OF), sexual desire (SD), and overall functioning (OF). A main effect for handedness was found on EF, OF, SD, and OS scales, with right-handed men showing higher functioning than left-handed men. Regarding interaction effects, the left-handed group of men showed greater decreased sexual functioning during tamoxifen (on three subscales: OF, SD, OS) compared to right-handed men. Further research should be conducted in order to support and refine this potential lateralized process of sexual neuromodulation within the brain.

Testosterone biases the amygdala toward social threat approach

Testosterone enhances amygdala reactions to social threat, but it remains unclear whether this neuroendocrine mechanism is relevant for understanding its dominance-enhancing properties; namely, whether testosterone biases the human amygdala toward threat approach. This pharmacological functional magnetic-resonance imaging study shows that testosterone administration increases amygdala responses in healthy women during threat approach and decreases it during threat avoidance. These findings support and extend motivational salience models by offering a neuroendocrine mechanism of motivation-specific amygdala tuning.

The link between testosterone and amygdala-orbitofrontal cortex connectivity in adolescent alcohol use

Alcohol consumption is one of the most problematic and widespread forms of risk taking in adolescence. It has been hypothesized that sex hormones such as testosterone play an important role in risk taking by influencing the development of brain networks involved in emotion and motivation, particularly the amygdala and its functional connections. Connectivity between the amygdala and the orbitofrontal cortex (OFC) may be specifically related to alcohol use, given the association of this tract with top-down control over behavioral approach tendencies. In line with this, prior studies in adults indicate a link between alcohol use and functional connectivity between the amygdala and the orbitofrontal cortex (OFC), as well as between testosterone and amygdala-OFC connectivity. We consolidated these research lines by investigating the association between alcohol use, testosterone and resting state functional brain connectivity within one large-scale adolescent sample (n=173, aged 12-25 years). Mediation analyses demonstrated an indirect effect of testosterone levels on alcohol use through amygdala-OFC intrinsic functional connectivity, but only in boys. That is, increased testosterone in boys was associated with reduced amygdala-OFC connectivity, which in turn was associated with increased alcohol intake. This study is the first to demonstrate the interplay between adolescent alcohol use, sex hormones and brain mechanisms, thus taking an important step to increase our understanding of the mechanisms behind this form of adolescent risk-taking.

Testosterone responses to competition predict decreased trust ratings of emotionally neutral faces

A wealth of evidence has linked individual differences in testosterone (T) to social, cognitive, and behavioral processes related to human dominance. Moreover, recent evidence indicates that a single administration of T reduces interpersonal trust in healthy young women. Here, in a sample of men and women (n=96), we investigated the extent to which endogenous fluctuations in T during a competitive interaction would predict subsequent ratings of trust from emotionally neutral faces. Results indicated that a rise in T predicted a decrease in trust ratings in men, but not women. These findings provide further support for the idea that competition-induced fluctuations in T may serve to modulate ongoing and/or future social behavior.

Does competition really bring out the worst? Testosterone, social distance and inter-male competition shape parochial altruism in human males

Parochial altruism, defined as increased ingroup favoritism and heightened outgroup hostility, is a widespread feature of human societies that affects altruistic cooperation and punishment behavior, particularly in intergroup conflicts. Humans tend to protect fellow group members and fight against outsiders, even at substantial costs for themselves. Testosterone modulates responses to competition and social threat, but its exact role in the context of parochial altruism remains controversial. Here, we investigated how testosterone influences altruistic punishment tendencies in the presence of an intergroup competition. Fifty male soccer fans played an ultimatum game (UG), in which they faced anonymous proposers that could either be a fan of the same soccer team (ingroup) or were fans of other teams (outgroups) that differed in the degree of social distance and enmity to the ingroup. The UG was played in two contexts with varying degrees of intergroup rivalry. Our data show that unfair offers were rejected more frequently than fair proposals and the frequency of altruistic punishment increased with increasing social distance to the outgroups. Adding an intergroup competition led to a further escalation of outgroup hostility and reduced punishment of unfair ingroup members. High testosterone levels were associated with a relatively increased ingroup favoritism and also a change towards enhanced outgroup hostility in the intergroup competition. High testosterone concentrations further predicted increased proposer generosity in interactions with the ingroup. Altogether, a significant relation between testosterone and parochial altruism could be demonstrated, but only in the presence of an intergroup competition. In human males, testosterone may promote group coherence in the face of external threat, even against the urge to selfishly maximize personal reward. In that way, our observation refutes the view that testosterone generally promotes antisocial behaviors and aggressive responses, but underlines its rather specific role in the fine-tuning of male social cognition.

Pubertal testosterone influences threat-related amygdala-orbitofrontal cortex coupling

Growing evidence indicates that normative pubertal maturation is associated with increased threat reactivity, and this developmental shift has been implicated in the increased rates of adolescent affective disorders. However, the neural mechanisms involved in this pubertal increase in threat reactivity remain unknown. Research in adults indicates that testosterone transiently decreases amygdala-orbitofrontal cortex (OFC) coupling. Consequently, we hypothesized that increased pubertal testosterone disrupts amygdala-OFC coupling, which may contribute to developmental increases in threat reactivity in some adolescents. Hypotheses were tested in a longitudinal study by examining the impact of testosterone on functional connectivity. Findings were consistent with hypotheses and advance our understanding of normative pubertal changes in neural systems instantiating affect/motivation. Finally, potential novel insights into the neurodevelopmental pathways that may contribute to adolescent vulnerability to behavioral and emotional problems are discussed.

Developmental trajectories of cortical-subcortical interactions underlying the evaluation of trust in adolescence

Social decision making is guided by the ability to intuitively judge personal attributes, including analysis of facial features to infer the trustworthiness of others. Although the neural basis for trustworthiness evaluation is well characterized in adults, less is known about its development during adolescence. We used event-related functional magnetic resonance imaging to examine age-related changes in neural activation and functional connectivity during the evaluation of trust in faces in a sample of adolescent females. During scanning, participants viewed masked presentations of faces and rated their trustworthiness. Parametric modeling of trust ratings revealed enhanced activation in amygdala and insula to untrustworthy faces, effects which peaked during mid-adolescence. Analysis of amygdala functional connectivity demonstrated enhanced amygdala-insula coupling during the evaluation of untrustworthy faces. This boost in connectivity was attenuated during mid-adolescence, suggesting a functional transition within face-processing circuits. Together, these findings underscore adolescence as a period of reorganization in neural circuits underlying socioemotional behavior.

Development of Risk Taking: Contributions from Adolescent Testosterone and the Orbito-frontal Cortex

The role of puberty in the development of risk taking remains poorly understood. Here, in a normative sample of 268 participants between 8 and 25 years old, we applied a psycho-endocrine neuroimaging approach to investigate the contribution of testosterone levels and OFC morphology to individual differences in risk taking. Risk taking was measured with the balloon analogue risk-taking task. We found that, corrected for age, higher endogenous testosterone level was related to increased risk taking in boys (more explosions) and girls (more money earned). In addition, a smaller medial OFC volume in boys and larger OFC surface area in girls related to more risk taking. A mediation analysis indicated that OFC morphology partly mediates the association between testosterone level and risk taking, independent of age. Mediation was found in such a way that a smaller medial OFC in boys potentiates the association between testosterone and risk taking but suppresses the association in girls. This study provides insights into endocrinological and neural underpinnings of normative development of risk taking, by indicating that OFC morphology, at least partly, mediates the association between testosterone and risk-taking behavior.

Neural correlates of explicit social judgments on vocal stimuli

Functional neuroimaging research on the neural basis of social evaluation has traditionally focused on face perception paradigms. Thus, little is known about the neurobiology of social evaluation processes based on auditory cues, such as voices. To investigate the top-down effects of social trait judgments on voices, hemodynamic responses of 44 healthy participants were measured during social trait (trustworthiness [TR] and attractiveness [AT]), emotional (happiness, HA), and cognitive (age, AG) voice judgments. Relative to HA and AG judgments, TR and AT judgments both engaged the bilateral inferior parietal cortex (IPC; area PGa) and the dorsomedial prefrontal cortex (dmPFC) extending into the perigenual anterior cingulate cortex. This dmPFC activation overlapped with previously reported areas specifically involved in social judgments on 'faces.' Moreover, social trait judgments were expected to share neural correlates with emotional HA and cognitive AG judgments. Comparison of effects pertaining to social, social-emotional, and social-cognitive appraisal processes revealed a dissociation of the left IPC into 3 functional subregions assigned to distinct cytoarchitectonic subdivisions. In total, the dmPFC is proposed to assume a central role in social attribution processes across sensory qualities. In social judgments on voices, IPC activity shifts from rostral processing of more emotional judgment facets to caudal processing of more cognitive judgment facets.

The evolutionary psychology of women's aggression

Evolutionary researchers have identified age, operational sex ratio and high variance in male resources as factors that intensify female competition. These are discussed in relation to escalated intrasexual competition for men and their resources between young women in deprived neighbourhoods. For these women, fighting is not seen as antithetical to cultural conceptions of femininity, and female weakness is disparaged. Nonetheless, even where competitive pressures are high, young women's aggression is less injurious and frequent than young men's. From an evolutionary perspective, I argue that the intensity of female aggression is constrained by the greater centrality of mothers, rather than fathers, to offspring survival. This selection pressure is realized psychologically through a lower threshold for fear among women. Neuropsychological evidence is not yet conclusive but suggests that women show heightened amygdala reactivity to threatening stimuli, may be better able to exert prefrontal cortical control over emotional behaviour and may consciously register fear more strongly via anterior cingulate activity. The impact of testosterone and oxytocin on the neural circuitry of emotion is also considered.

Pyrrhic victories: the need for social status drives costly competitive behavior

Competitive behavior is commonly defined as the decision to maximize one's payoffs relative to others. We argue instead that competitive drive derives from a desire for social status. We make use of a multi-player auction task in which subjects knowingly incur financial losses for the sake of winning auctions. First, we show that overbidding is increased when the task includes members of a rival out-group, suggesting that social identity is an important mediator of competitiveness. In addition, we show that the extent that individuals are willing to incur losses is related to affective responses to social comparisons but not to monetary outcomes. Second, we show that basal levels of testosterone predict overbidding, and that this effect of testosterone is mediated by affective responses to social comparisons. Based on these findings, we argue that competitive behavior should be conceptualized in terms of social motivations as opposed to just relative monetary payoffs.