The relationship between testosterone and aggression: a meta-analysis

In non-human animals, the relationship between testosterone and aggression is well established. In humans, the relationship is more controversial. To clarify the relationship, Archer conducted three meta-analyses and found a weak, positive relationship between testosterone and aggression. Unfortunately, each of the analyses included only five to six studies. The aim of the present study was to re-examine the relationship between testosterone and aggression with a larger sample of studies. The present analyses are based on 45 independent studies (N=9760) with 54 independent effect sizes. Only studies that reported a p-value or effect size were included in the analyses and the sample may underestimate the proportion of non-significant findings in the population. Correlations ranged from −0.28 to 0.71. The mean weighted correlation (r=0.14) corroborates Archer's finding of a weak positive relationship.     

Hormones and aggression in childhood and adolescence

This review is a survey on recent psychobiosocial studies on association between hormones and aggression/violence in children and adolescents, with a special focus on puberty, given the rapid changes in both hormones and behavior occurring during that developmental period. Since it cannot be assumed that all readers have much background knowledge, it inevitably begins with some comments about the concept and multifaceted nature of aggression, as well as with a brief reminding about hormone candidates to be linked to aggression during human development. Then, we finish off with the status of its knowledge in today's science, tackling in a systematic way with the main data published, hormone by hormone. The origin of the gender-based differences in aggression must lie in neuroendocrinological events occurring during prenatal life or early in postnatal life. A complex and indirect effect of testosterone on aggression is proposed. A low HPA axis activity seems associated with chronic aggressive and antisocial behaviors. It is also suggested that early adrenal androgens contribute to the onset and maintenance of persistent violent and antisocial behavior, and that it begins early in life and persists into adulthood, at least in young boys. There are also some studies suggesting an association between aggression and some pituitary hormones in children, even if present data are still far from being consistent. The hormone-aggression link during development thus is not consistently reported. There can be an indirect relation in three ways: hormones can be involved in the development of aggression as a cause, as a consequence, or even as a mediator. Psychosocial factors may influence the causation and progression of violence in children through hormonal action.     

The frontal lobe and aggression

Frontal lesions often lead to psychosocial problems. It is not surprising that frontal lobe dysfunctions have been proposed to underlie antisocial behaviour in individuals without apparent lesions. However, physical aggression and violence have never been systematically related to acquired lesions. Whereas, traditional neuropsychological testing identifies problems in cognitive and emotional information processing, recent brain-imaging studies have revealed both the frontal structural and functional underpinnings of antisocial behaviour. Careful characterization of antisocial behaviour subtypes seems to indicate that cognitive-neuropsychological function is systematically poor in physical aggression and hyperactivity. Recent refinements point to biological and genetic moderators of that association.     

Predictors of aggression in Southeast Asian female prisoners

Although aggression is universal, few studies examine violence from an Asian perspective, and even fewer consider female offenders from Southeast Asia. The current study examined whether correlates of aggression in western male offenders are similarly effective for predicting aggression in female inmates (n = 114) from a local prison in Singapore. Aggression was measured using the Buss–Perry Aggression Questionnaire (comprising dimensions of physical and verbal aggression, anger and hostility) which we sought to predict from measures of impulsivity, general personality traits (neuroticism, agreeableness), psychopathy, and empathy. Impulsivity and agreeableness were significant predictors of self-reported physical and verbal aggression and anger, whereas neuroticism contributed to anger. Neuroticism and psychopathy were significant predictors of hostility. Empathy did not significantly predict any of the four aggression dimensions. Personality, impulsivity and psychopathy appear fair predictors of aggression for female offenders from Southeast Asia, just as they are for the western male offenders.     

Violence restrained: Effects of self-regulation and its depletion on aggression

Aggressive impulses arise from many factors, but they are usually held in check by social norms for self-control. Thus, the proximal cause of aggression is often failure of self-restraint. In five studies, depleted capacity for self-regulation (caused by prior, even irrelevant acts of self-regulation) increased aggressive responding, especially after an insulting provocation. When participants were insulted and their self-regulatory strength was depleted (i.e., after completing previous tasks that required self-regulation), participants were more likely to aggress. When the urge to aggress was relatively weaker (i.e., when participants were not insulted), self-regulatory depletion did not increase aggressive behavior. This effect was moderated by trait self-control: Participants low in trait self-control were particularly likely to express intentions of behaving aggressively in response to provocation, whereas participants high in trait self-control did not express intentions of responding aggressively. Laboratory, autobiographical memory, and hypothetical responses confirmed the pattern.     

Neighborhood violent crime and adolescent relationship aggression

Research has shown that neighborhoods play a role in the etiology of violence. However, few adolescent relationship aggression (ARA) studies have objective measures of violent neighborhoods. Drawing on a nationally representative sample of youth, this study examines the association between ARA and local levels of violent crime (measured using geocoded Uniform Crime Report data from each of the youths’ residential neighborhoods). Study analyses are based on survey data from 723 youth (ages 10–18) in current or recent dating relationships (351 males and 372 females) in the Survey on Teen Relationships and Intimate Violence (STRiV), a national representative household panel survey exploring interpersonal violence and related aggression among adolescents. About 19% of the sample reported ARA victimization in their most recent dating relationship (ARA perpetration was 17%). Neighborhood violent crime in the study (males living in 86.9 and females 99.8) was slightly lower than the national average of 100. With a broad national sample, 40% non-Whites, hypotheses guided by theories of neighborhood influence were tested. The study did not find an association between neighborhood violent crime and ARA victimization and perpetration, controlling for key demographic factors. The results, for a broad range of high- and low-crime neighborhoods, suggest that neighborhood violence does not seem to affect individual rates of ARA. The results suggest the ARA victimization and perpetration are perhaps ubiquitous and found both in low and high violent crime neighborhoods, suggesting that addressing local violent crime rates alone does not seem to be a path to also reducing ARA.     

Modularity in everyday life judgments of aggression and violent behavior

This review focuses on one aspect of moral judgment of aggression and violent behavior in the context of the psychodynamics of everyday life: Judgmental modularity. The central hypothesis asserts that, from the victim's perspective, the severity of judgments or the relative weight assigned to physical damage, when information on intent and damage is available, will be maximized, whereas inverse trends will typify the judgments of the same person from the assailant's perspective. This view resembles the spirit of the functional approach to moral judgment of violent behavior. In this light, related studies that were conducted within the framework of functional measurement are reviewed. Judgmental modularity was documented in the majority of the findings. However, in two studies, the same participants exhibited judgmental consistency in the first phase and judgmental modularity in a second phase, which manipulated other types of judgmental perspectives. Implications for the issue of judgmental modularity, for the issue of modularity in violent behavior and for a proposal to establish a functional definition of aggression are discussed.     

Laboratory and questionnaire measures of aggression among female parolees with violent or nonviolent histories

Female parolees were recruited into a laboratory study to determine the relationship between their previous aggression history, questionnaire measures of aggression, and behavioral measures of aggressive responding using a laboratory methodology: the Point Subtraction Aggression Paradigm (PSAP). Subjects were assigned to a violent or nonviolent group based on their criminal history. Subjects participated in sessions in which they were given three response options: (1) nonaggressive responding that earned money, (2) aggressive responding that ostensibly subtracted money from another fictitious person and was defined as aggressive since it resulted in the ostensible delivery of an aversive stimulus (subtraction of money) to another person, and (3) escape responding that protected the subject's earnings from periodic subtractions initiated by the fictitious other person. Results indicated that the violent female parolees emitted significantly more aggressive responses than subjects in the nonviolent group. This study provides additional external validity as well as evidence for convergent and discriminant validity for PSAP laboratory measurement of human aggressive responding and extends these findings to female parolees. Comparisons to previously published data with male parolees showed that gender differences were found among violent but not nonviolent parolees. Aggr. Behav. 26:291–307, 2000. © 2000 Wiley‐Liss, Inc.     

The effect of the amount of blood in a violent video game on aggression, hostility, and arousal

The current study utilized the General Aggression Model, with an emphasis on aggression-related priming, to explore the different effects on hostility, physiological arousal, and state aggression in those who played a violent video game (Mortal Kombat: Deadly Alliance) with differing levels of blood (maximum, medium, low, and off). Simple effects analyses showed that those in the maximum blood and medium blood conditions had a significant increase in hostility and physiological arousal, while those in the low blood and no blood conditions did not have such an increase in arousal and hostility. Further analyses indicated that those in the maximum and medium blood conditions used the character’s weapon significantly more often than those in the low and blood absent conditions. Implications and future research are discussed.     

This is your brain on violent video games: Neural desensitization to violence predicts increased aggression following violent video game exposure

Previous research has shown that media violence exposure can cause desensitization to violence, which in theory can increase aggression. However, no study to date has demonstrated this association. In the present experiment, participants played a violent or nonviolent video game, viewed violent and nonviolent photos while their brain activity was measured, and then gave an ostensible opponent unpleasant noise blasts. Participants low in previous exposure to video game violence who played a violent (relative to a nonviolent) game showed a reduction in the P3 component of the event-related brain potential (ERP) to violent images (indicating physiological desensitization), and this brain response mediated the effect of video game content on subsequent aggressive behavior. These data provide the first experimental evidence linking violence desensitization with increased aggression, and show that a neural marker of this process can at least partially account for the causal link between violent game exposure and aggression.     

An empirical examination of sex differences in scoring preschool children's aggression

Sex differences in adults’ observations and ratings of children’s aggression was studied in a sample of preschool children (N = 89, mean age = 44.00 months, SD = 8.48). When examining the direct observations made by trained observers, male observers, relative to female observers, more frequently recorded aggressive bouts, especially of boys. On rating scales assessing aggression, trained male raters also gave higher aggressive ratings than female raters. Lastly, we compared the ratings of trained female raters and female teachers on the same scale and found no differences. Results are discussed in terms male raters’ and observers’ prior experiences in activating their experiential schemata where males’ greater experience in aggression, relative to that of females, leads them to perceive greater levels of aggression.     

Facial affect recognition deficits: A potential contributor to aggression in psychotic illness

The current literature suggests a relationship between psychosis and the likelihood of engaging in aggressive behavior, though the factors involved are unclear. In this paper we use a social information processing framework to consider mediators of aggressive behavior in psychosis, especially facial affect recognition (FAR) deficits. The theoretical underpinnings of aggressive behavior are explored using the General Aggression Model (GAM) and FAR deficits are posited as a possible contributor to increased aggression in psychosis. Current research investigating the relationship between FAR, psychosis, and aggression is critically examined, and the role of potential confounding variables including positive symptoms, psychopathic personality traits, childhood trauma, and substance use briefly explored. In conclusion, we argue that socioemotional processing deficits, such as impaired FAR, are a fruitful area for research aimed at understanding, and hence reducing the risk of violence in psychosis.     

Suicidal and violent behavior: The role of anger,emotion dysregulation,and impulsivity

Suicidality and violence are serious public health problems. A rich literature supports the relationship between suicidality and violence, including common associations with trait anger. However, less is known about how trait anger may facilitate these behaviors. Two potential mechanisms in this relationship are emotion dysregulation and impulsivity, both of which are linked to increased anger, suicidality, and violence. We investigated anger as a common underlying factor for both suicidal and violent behavior, and emotion dysregulation and impulsivity (i.e., negative and positive urgency) as potential mediators in this relationship. Results demonstrate that trait anger was associated with both suicidal and violent behavior. Further, emotion dysregulation mediated the anger and suicidal behavior relationship whereas both negative and positive urgency mediated the anger and violent behavior relationship. Although trait anger may be a common underlying factor for both suicidal and violent behavior, the nature of these relationships seems to vary significantly.     

Anger,aggression, risky behavior,and crash-related outcomes in three groups of drivers

High anger drivers who acknowledged problems with driving anger and were interested in treatment were compared to high and low anger drivers who did not acknowledge problems with driving anger or want treatment. Although high anger drivers who acknowledged problems reported greater anger on two measures than high anger drivers who did not acknowledge problems, both high anger groups tended not to differ from one another and were more frequently and intensely angered when driving, reported more aggressive and less adaptive/constructive forms of expressing anger while driving, engaged in more aggressive and risky behavior on the road, and experienced more of some accident-related outcomes than low anger drivers. High anger groups did not differ from each other, but reported more trait anxiety and anger and more outward negative and less controlled general anger expression than the low anger group. The two groups of high anger drivers, however, require different types of interventions given their state of readiness for driving anger reduction. Results were also interpreted as supportive of the state-trait model of anger and construct validity of the Driving Anger Scale.     

Risk and dynamics of violence in Asperger's syndrome: A systematic review of the literature

The main purpose of this article is to delineate findings from a review of the literature on the empirical basis for the existence of a relationship between Asperger's syndrome (AS) and violence risk. A second aim is to examine whether certain characteristics of the disorder may have a higher violence-triggering potential. Results of this review show that there are very few empirical studies that confirm a stable link between AS and violence. Only 11 studies involving 22 patients and 29 violent incidents met the criteria for inclusion in the review after the search of the literature. However, a qualitative analysis of the studies yielded some indications of possible patterns of dynamics of violence that may prove to be typical of persons with AS. A tentative comparison of AS and psychopathy indicated that there may be qualitative differences in the characteristics of violent behavior between the disorders. Suggestions for further research are presented.     

Defensive self-esteem and aggression in childhood

Research examining the association between self-esteem (SE) and aggressive behavior in childhood has produced mixed findings. Some of the confusion may stem from the fact that researchers have relied on explicit measures of SE, thus conflating two distinct types of positive self-regard: secure SE (characterized by high levels of explicit and implicit SE), and defensive SE (characterized by high levels of explicit but low levels of implicit SE). The current study tested the hypothesis that children with high levels of defensive, but not secure, SE would engage in higher levels of aggressive behavior. Ninety-three children completed measures of both explicit and implicit SE. Teachers assessed children’s level of physical and relational aggression in the school setting. As predicted, there was a positive association between explicit SE and aggression when levels of implicit SE were low, but not when levels of implicit SE were high.