The nature of human aggression

The Val158Met Polymorphism in 8-Year-Old Boys and Girls Moderates the Influence of Parenting Styles on Proactive Aggression: Testing the Sensitivity to the Environment

The aim of the study was to explore the possible vulnerability (diathesis-stress), susceptibility (differential susceptibility), or vantage (vantage sensitivity) properties of COMT gen Val158Met polymorphism to adverse and favorable parenting styles from both parents in relation to children's reactive and proactive aggressive behavior. Within 279 eight-year-old children (125 girls and 154 boys) from Spain, reactive and proactive aggressive behavior was measured through the "Reactive and Proactive Questionnaire" (RPQ). Saliva samples were collected to genotype for the COMT Val158Met polymorphism via real-time PCR. Finally, parenting styles were assessed using the "Parenting Styles and Dimensions Questionnaire" (PSDQ). The results revealed that for boys, the Met allele was a vulnerability factor for proactive aggression in response to low-authoritative parenting from the father. For girls, it was the Val allele, the vulnerability variable to the high authoritarian style of the father, and the susceptibility factor to the authoritative style of the mother over proactive aggression. The results are discussed, considering possible sex differences. Our results indicate that the COMT Val158Met polymorphism is a biological variable that confers greater sensitivity to the environment.

Fame through surprise: How fame-seeking mass shooters diversify their attacks

Mass shootings are becoming more frequent in the United States, as we routinely learn from the media about attempts that have been prevented or tragedies that destroyed entire communities. To date, there has been limited understanding of the modus operandi of mass shooters, especially those who seek fame through their attacks. Here, we explore whether the attacks of these fame-seeking mass shooters were more surprising than those of others and clarify the link between fame and surprise in mass shootings. We assembled a dataset of 189 mass shootings from 1966 to 2021, integrating data from multiple sources. We categorized the incidents in terms of the targeted population and shooting location. We measured "surprisal" (often known as "Shannon information content") with respect to these features, and we scored fame from Wikipedia traffic data-a commonly used metric of fame. Surprisal was significantly higher for fame-seeking mass shooters than non-fame-seeking ones. We also registered a significant positive correlation between fame and surprisal controlling for the number of casualties and injured victims. Not only do we uncover a link between fame-seeking behavior and surprise in the attacks but also we demonstrate an association between the fame of a mass shooting and its surprise.

Convergence on reduced aggression through shared behavioral traits in multiple populations of Astyanax mexicanus

Background

Results

Conclusion

Supplementary information

Lateral Hypothalamus Calcium/Calmodulin-Dependent Protein Kinase II α Neurons Encode Novelty-Seeking Signals to Promote Predatory Eating

Predatory hunting is an innate appetite-driven and evolutionarily conserved behavior essential for animal survival, integrating sequential behaviors including searching, pursuit, attack, retrieval, and ultimately consumption. Nevertheless, neural circuits underlying hunting behavior with different features remain largely unexplored. Here, we deciphered a novel function of lateral hypothalamus (LH) calcium/calmodulin-dependent protein kinase II α (CaMKIIα+) neurons in hunting behavior and uncovered upstream/downstream circuit basis. LH CaMKIIα+ neurons bidirectionally modulate novelty-seeking behavior, predatory attack, and eating in hunting behavior. LH CaMKIIα+ neurons integrate hunting-related novelty-seeking information from the medial preoptic area (MPOA) and project to the ventral periaqueductal gray (vPAG) to promote predatory eating. Our results demonstrate that LH CaMKIIα+ neurons are the key hub that integrate MPOA-conveyed novelty-seeking signals and encode predatory eating in hunting behavior, which enriched the neuronal substrate of hunting behavior.

Differential Susceptibility or Diathesis-Stress: Testing the Moderating Role of Temperament and Cortisol Levels between Fathers' Parenting and Children's Aggressive Behavior

Aggression is a multidimensional behavior that could be caused by different biopsychosocial variables. The aim of this study was to explore whether temperament, cortisol and sex moderate the relation between fathers’ parenting style and aggressive behavior in school-aged children, and whether this corresponds to differential susceptibility or diathesis-stress. Participants were 158 children (88 boys and 70 girls) aged 8 years. Aggressive behavior was measured using the Direct and Indirect Aggression Scale and fathers informed about their child’s temperament and their own parenting style through the Children’s Behavior Questionnaire and the Parenting Styles and Dimensions Questionnaire (respectively). Children’s’ baseline saliva cortisol levels were analyzed through an enzyme immunoassay technique. The results revealed that high cortisol levels moderated the relation between fathers’ low levels of authoritative parenting and boys’ aggression. Moreover, high negative emotionality moderated the relation between permissive paternal parenting and girls’ aggressive behavior, with both these relations being consistent with the diathesis-stress theory.

Self-report versus clinician-ratings in the assessment of aggression in violent offenders

BACKGROUND

The construct of aggression is central to work with violent offenders, but it is a broad construct that can be assessed by many different methods and instruments. Its measurement may, however, have profound implications for treatment planning. We need more knowledge about how different methods for assessing aggression relate to each other.

AIMS

Our aims were to investigate, first, the convergence and concordance of two methods of assessing aggression: self-report and clinical assessment and, second, to determine the degree to which aggression can be discriminated from neighbouring constructs, such as hostility, anger and criminal behaviour.

METHODS

A nationally representative Swedish cohort of 269 18-25-year-old incarcerated violent offenders was recruited. Data were collected through structured self-reports of aggression, anger and hostility traits (Aggression Questionnaire-Revised Swedish Version) and clinical assessments of lifetime prevalence of aggressive and antisocial behaviours (Life History of Aggression). Criminal records were retrieved from the Swedish National Crime Register.

RESULTS

Self-ratings and clinician-ratings of aggression were highly convergent and concordant, especially regarding physical aggression. Violent offence records were weakly, if at all, correlated, while self-reported hostility was weakly, or not at all, correlated with self-reported or with clinician-rated aggression. There was an inverse relationship between aggression and criminal records of sexual offences.

CONCLUSIONS AND IMPLICATIONS

Even though a combination of self-reports and clinician-ratings may provide a better overview of an individual's aggressive behaviours, our results indicate that they yield such similar information that either alone would be sensitive enough. Our results do not, however, support using one of these methods as a proxy for the other since choice of measure and accepted concordance between them depend on the context within which the assessment is conducted. We reconfirmed that official records of violent offending are unlikely to be adequate measures of outcome after interventions to reduce aggressive behaviours.

Aggression Amongst Outpatients With Schizophrenia and Related Psychoses in a Tertiary Mental Health Institution

Aims: Aggression is defined as "any behavior intended to cause physical, emotional, or psychological harm to another." The aims of the current study were to (i) examine underlying factor structure of the Buss-Perry Aggression Questionnaire (BPAQ) and (ii) explore socio-demographic and clinical correlates (symptom severity, substance use and alcohol use) among patients with schizophrenia and related psychoses in a multi-ethnic Asian population. Methods: Data collected from 397 participants who were seeking outpatient treatment for schizophrenia and related psychoses at a tertiary psychiatric hospital were included in the analyses. BPAQ, a 29-item, four-factor instrument that measures physical aggression, verbal aggression, anger and hostility was used to assess aggression. Data on socio-demographic variables, age of onset of illness, drug use, alcohol use and symptom severity were also collected. Confirmatory factor analysis (CFA) was performed to establish the underlying factor structure of the BPAQ. Multiple regression analyses were utilized to examine socio-demographic and clinical correlates of the BPAQ factors. Results: The mean age of the participants was 36.2 years (SD = 10.9, range: 21-65). Factor structure obtained from the CFA indicated that a higher order four-factor solution had an acceptable fit to the observed data (WLSMV χ² = 1,025.35, df = 320, RMSEA = 0.07, CFI = 0.94, TLI = 0.93, SRMR = 0.05). Females had lower physical aggression and hostility scores as compared to males. Those with lower education had higher physical aggression scores as compared to those with higher education. Participants who received a diagnosis after the age of 30 years had higher physical aggression and anger scores as compared to those who received a diagnosis at or before 20 years of age. Symptom severity was positively associated with higher BPAQ scores. Conclusion: The study findings demonstrated high internal consistency and applicable measurement factor structure of BPAQ in this study sample, making it an appropriate questionnaire for assessing aggressive behavior in this population. We also identified socio-demographic and clinical factors that were associated with aggression in patients with schizophrenia and related psychoses.

The role of monoamine oxidase A in the neurobiology of aggressive, antisocial, and violent behavior: A tale of mice and men

Over the past two decades, research has revealed that genetic factors shape the propensity for aggressive, antisocial, and violent behavior. The best-documented gene implicated in aggression is MAOA (Monoamine oxidase A), which encodes the key enzyme for the degradation of serotonin and catecholamines. Congenital MAOA deficiency, as well as low-activity MAOA variants, has been associated with a higher risk for antisocial behavior (ASB) and violence, particularly in males with a history of child maltreatment. Indeed, the interplay between low MAOA genetic variants and early-life adversity is the best-documented gene × environment (G × E) interaction in the pathophysiology of aggression and ASB. Additional evidence indicates that low MAOA activity in the brain is strongly associated with a higher propensity for aggression; furthermore, MAOA inhibition may be one of the primary mechanisms whereby prenatal smoke exposure increases the risk of ASB. Complementary to these lines of evidence, mouse models of Maoa deficiency and G × E interactions exhibit striking similarities with clinical phenotypes, proving to be valuable tools to investigate the neurobiological mechanisms underlying antisocial and aggressive behavior. Here, we provide a comprehensive overview of the current state of the knowledge on the involvement of MAOA in aggression, as defined by preclinical and clinical evidence. In particular, we show how the convergence of human and animal research is proving helpful to our understanding of how MAOA influences antisocial and violent behavior and how it may assist in the development of preventative and therapeutic strategies for aggressive manifestations.

The Role of Traumatic Childhood Experiences in Predicting a Disposition to Risk-Taking and Aggression in Turkish University Students

The purpose of this research was to determine whether or not traumatic childhood experiences in childhood predict a disposition to risk-taking and aggression among university students. The participants consisted of 851 students: 477 (56.1%) females and 374 (43.9%) males attending various faculties at the Karadeniz Technical University in Turkey. The Childhood Trauma Questionnaire, Adolescent Risk-Taking Scale, Aggression Questionnaire, and Personal Information Form were used for data collection. The analysis results revealed a positive correlation between traumatic experiences (physical, sexual, emotional maltreatment, and emotional neglect) and risk-taking and aggression. Physical and sexual abuse and gender are significant predictors of risk-taking. Physical abuse and gender are some of the predictors of aggression. Another finding from the study is that physical and emotional abuse and emotional neglect vary by gender. This study concludes that exposure to traumatic experiences in childhood prepares the foundation for negative behaviors in adulthood.

Age differences in aggression in Bulgarian primary school age children

In order to study the age differences of the status of aggression from the beginning to the end of the primary school age, 244 typically developing Bulgarian children were examined with the adapted for Bulgarian population questionnaire for measurement of aggression and depression in primary school age children. The total sample was divided into 2 age groups: first graders’ group (6-8 years, Mean age = 6.99, SD = 0.189; N = 82; 42 girls) and fourth graders’ group (9-11 years; Mean age = 10.23, SD = 0.450; N = 162; 79 girls). It was suggested that age-related differences in aggression status were present in the age range considered. It was also assumed that there were some gender differences in the participants’ aggressive status. The results did not reveal any statistically significant differences between the two age groups in the mean aggression scores, suggesting no essential aggression change in this age period. As regards to the effect of the participant’s gender, some statistically significant differences between the age subgroups in the mean aggression scores were found, with the boys demonstrated higher aggression than girls, suggesting that the subjects’ sex was a factor with significant effect on the level of aggression in this age period.

Aggressive Behavior in School-aged Children: Clusters based on Anger, Empathy and Testosterone and Cortisol Measures

The aim of this piece of research was to study the existence of clusters based on anger, empathy and cortisol and testosterone measures associated with aggressive behavior in school-aged children. The sample group comprised 139 eight-year-old children (80 boys and 59 girls). Aggressive behavior was measured using the Direct and Indirect Aggression Scale. Both psychological and biological variables were used to determine psychobiological profiles. The psychological variables considered were trait anger, measured using the State-Trait Anger Expression Inventory for Children and Adolescents, and empathy, measured using the Empathy Quotient-Child Version. Testosterone and cortisol concentrations were measured through saliva samples and analyzed using an ELISA (Enzyme-linked immunosorbent assay). A Cluster Analysis revealed three clusters which were clearly different as regards their psychological and biological characteristics. The analysis of variance (ANOVA) revealed that the cluster characterized by having higher anger levels, lower empathy levels and higher testosterone and cortisol levels was more aggressive than the other two (p < .0001, η2 = .19). The results indicate that studying psychological and biological variables together may help establish differentiated aggression patterns among children.

Cannabidiol attenuates aggressive behavior induced by social isolation in mice: Involvement of 5-HT1A and CB1 receptors

Long-term single housing increases aggressive behavior in mice, a condition named isolation-induced aggression or territorial aggression, which can be attenuated by anxiolytic, antidepressant, and antipsychotic drugs. Preclinical and clinical findings indicate that cannabidiol (CBD), a non-psychotomimetic compound from Cannabis sativa, has anxiolytic, antidepressant, and antipsychotic properties. Few studies, however, have investigated the effects of CBD on aggressive behaviors. Here, we investigated whether CBD (5, 15, 30, and 60 mg/kg; i.p.) could attenuate social isolation-induced aggressive behavior in the resident-intruder test. Male Swiss mice (7-8 weeks) were single-housed for 10 days (resident mice) to induce aggressive behaviors, while conspecific mice of same sex and age (intruder mice) were group-housed. During the test, the intruder was placed into the resident's home-cage and aggressive behaviors initiated by the resident, including the latency for the first attack, number of attacks, and total duration of aggressive encounters, were recorded. The involvement of 5-HT1A and CB1 receptors (CB1R) in the effects of CBD was also investigated. All tested CBD doses induced anti-aggressive effects, indicated by a decrease in the number of attacks. CBD, at intermediary doses (15 and 30 mg/kg), also increased latency to attack the intruder and decreased the duration of aggressive encounters. No CBD dose interfered with locomotor behavior. CBD anti-aggressive effects were attenuated by the 5-HT1A receptor antagonist WAY100635 (0.3 mg/kg) and the CB1 antagonist AM251 (1 mg/kg), suggesting that CBD decreases social isolation-induced aggressive behaviors through a mechanism associated with the activation of 5-HT1A and CB1 receptors. Also, CBD decreased c-Fos protein expression, a neuronal activity marker, in the lateral periaqueductal gray (lPAG) in social-isolated mice exposed to the resident-intruder test, indicating a potential involvement of this brain region in the drug effects. Taken together, our findings suggest that CBD may be therapeutically useful to treat aggressive behaviors that are usually associated with psychiatric disorders.

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.

The principle of consistency and the cause and function of behaviour

At all levels of information processing in the brain, neural and cognitive structures tend towards a state of consistency. When two or more simultaneously active cognitive structures are logically inconsistent, arousal is increased, which activates processes with the expected consequence of increasing consistency and decreasing arousal. Increased arousal is experienced as aversive, while the expected or actual decrease in arousal as a result of increased consistency is experienced as rewarding. Modes of resolution of inconsistency can be divided into purely cognitive solutions, such as changing an attitude or an associated motor plan, and behavioural solutions, such as exploration, aggression, fear, and feeding. Models and theories consistent with the principle of consistency are numerous, have a long and continuing history, and come from many different scientific fields, such as social psychology, perception, neurocognition, learning, motor control, system control, ethology, and stress. The present paper presents a brief overview of relevant information from these fields of research, while focusing mainly on the implications of the principle of consistency for the understanding of the cause and function of behaviour. Based on this overview, it is proposed that all behaviour involving cognitive processing is caused by the activation of inconsistent cognitions and functions to increase perceived consistency.

Comparing Postnatal Development of Gonadal Hormones and Associated Social Behaviors in Rats, Mice, and Humans

Postnatal development includes dramatic changes in gonadal hormones and the many social behaviors they help regulate, both in rodents and humans. Parental care-seeking is the most salient social interaction in neonates and infants, play and prosocial behaviors are commonly studied in juveniles, and the development of aggression and sexual behavior begins in peripubertal stages but continues through late adolescence into adulthood. Although parental behaviors are shown after reproductive success in adulthood, alloparenting behaviors are actually high in juveniles as well. These behaviors are sensitive to both early-life organizational effects of gonadal hormones and later-life activational regulation. However, changes in circulating gonadal hormones and the display of the previous behaviors over development differ between rats, mice, and humans. These endpoints are of interest to endocrinologist, toxicologists, and neuroscientists because of their relevance to mental health disorders and their vulnerability to effects of endocrine-disrupting chemical exposure. As such, the goal of this mini-review is to succinctly describe and relate the postnatal development of gonadal hormones and social behaviors to each other, over time, and across animal models. Ideally, this will help identify appropriate animal models and age ranges for continued study of both normative development and in contexts of environmental disruption.

Battle of Wits

Political conservatism and threat salience have been consistently associated with intergroup bias. However, prior research has not examined potential effects of conservatism and/or threat on the attribution of relative in-group/out-group intelligence. In a cross-cultural study conducted in Spain and the United Kingdom, priming violent conflict with ISIS led participants to view an in-group ally as relatively more intelligent than an out-group adversary, in an effect mediated by feelings of anger (but not fear or general arousal). Conservatism similarly predicted biased perception of the ally’s relative intellect, a tendency that was driven by militaristic (not social/fiscal) political attitudes but was not explained by associated increases in state anger following conflict cues. This overall pattern indicates that conflict cues and militaristic political orientation heighten assessments of relative intergroup intellect during warfare via distinct affective and attitudinal pathways.

Psicobiología de la agresión y la violencia

El presente trabajo expone la revisión y análisis de distintas investigaciones realizadas por múltiples autores quienes han aportado valiosos descubrimientos para la comprensión de las conductas agresivas y los comportamientos violentos de los seres humanos. La agresión y la violencia son conductas bastante complejas que, en dosis moderadas, pueden tener unafunción adaptativa en entornos ambientales exigentes que supongan retos para la supervivencia del individuo. De este modo, la agresión y la violencia podrían considerarse como parte de una misma dimensión continua (Vassos, 2014). Diversos factores psicobiológicos convergen e interactúan en el marco de las causas y consecuencias de la agresión y la violencia, como las bases genéticas (genes y herencia), la neuroquímica del cerebro (neurotransmisores y hormonas), las estructuras subcorticales (hipotálamo, amígdala, corteza cingulada anterior, fascículo uncinado), el desempeño de la corteza prefrontal y las funciones ejecutivas (corteza orbitofrontal, corteza ventromedial, corteza dorsolateral). No podemos olvidar la interacción de los factores anteriormente mencionados con la interacción e influencia de los factores ambientales, psicosociales y culturales en la manifestación de actos violentos por parte de los seres humanos

The role of central and medial amygdala in normal and abnormal aggression: A review of classical approaches

The involvement of the amygdala in aggression is supported by overwhelming evidence. Frequently, however, the amygdala is studied as a whole, despite its complex internal organization. To reveal the role of various subdivisions, here we review the involvement of the central and medial amygdala in male rivalry aggression, maternal aggression, predatory aggression, and models of abnormal aggression where violent behavior is associated with increased or decreased arousal. We conclude that: (1) rivalry aggression is controlled by the medial amygdala; (2) predatory aggression is controlled by the central amygdala; (3) hypoarousal-associated violent aggression recruits both nuclei, (4) a specific upregulation of the medial amygdala was observed in hyperarousal-driven aggression. These patterns of amygdala activation were used to build four alternative models of the aggression circuitry, each being specific to particular forms of aggression. The separate study of the roles of amygdala subdivisions may not only improve our understanding of aggressive behavior, but also the differential control of aggression and violent behaviors of various types, including those associated with various psychopathologies.

The role of intrinsic and extrinsic rewards in committing violence during combat: A cross-sectional study with former combatants in the DR Congo

It has been postulated that the violent behavior that characterizes armed conflict is reinforced by the possibility of receiving rewards. The present study examined the potential influence of two types of rewards in an ongoing setting of conflict: extrinsic and intrinsic rewards. Former combatants active in the Democratic Republic of the Congo (N = 198) were interviewed and questioned about the way they were recruited, the offenses they committed during combat, their level of perceived intrinsic rewards (i.e., appetitive perception of violence), and the number of received extrinsic rewards during their time in the armed group (e.g., money, extra food, alcohol, or drugs). A moderated multiple regression analysis showed that the number of received extrinsic rewards and the level of intrinsic rewards were significantly positively related to the number of different types of offenses committed. In contrast to our expectations and previous findings, the recruitment type (forced conscription vs. voluntary enlistment) did not moderate this relation. Our findings suggest that both types of rewards play a role in committing violence during combat. We suggest, therefore, that reintegration programs should not only consider the influence of extrinsic rewards, but also need to address the influence of intrinsic rewards to counter violent behavior among former combatants. Aggr. Behav. 43:241-250, 2017. © 2016 Wiley Periodicals, Inc.

Chronic social instability in adult female rats alters social behavior, maternal aggression and offspring development

We investigated the consequences of chronic social instability (CSI) during adulthood on social and maternal behavior in females and social behavior of their offspring in a rat model. CSI consisted of changing the social partners of adult females every 2-3 days for 28 days, 2 weeks prior to mating. Females exposed to CSI behaved less aggressively and more pro-socially towards unfamiliar female intruders. Maternal care was not affected by CSI in a standard testing environment, but maternal behavior of CSI females was less disrupted by a male intruder. CSI females were quicker to attack prey and did not differ from control females in their saccharin consumption indicating, respectively, no stress-induced sensory-motor or reward system impairments. Offspring of CSI females exhibited slower growth and expressed more anxiety in social encounters. This study demonstrates continued adult vulnerability to social challenges with an impact specific to social situations for mothers and offspring.

The phylogenetic roots of human lethal violence

The psychological, sociological and evolutionary roots of conspecific violence in humans are still debated, despite attracting the attention of intellectuals for over two millennia. Here we propose a conceptual approach towards understanding these roots based on the assumption that aggression in mammals, including humans, has a significant phylogenetic component. By compiling sources of mortality from a comprehensive sample of mammals, we assessed the percentage of deaths due to conspecifics and, using phylogenetic comparative tools, predicted this value for humans. The proportion of human deaths phylogenetically predicted to be caused by interpersonal violence stood at 2%. This value was similar to the one phylogenetically inferred for the evolutionary ancestor of primates and apes, indicating that a certain level of lethal violence arises owing to our position within the phylogeny of mammals. It was also similar to the percentage seen in prehistoric bands and tribes, indicating that we were as lethally violent then as common mammalian evolutionary history would predict. However, the level of lethal violence has changed through human history and can be associated with changes in the socio-political organization of human populations. Our study provides a detailed phylogenetic and historical context against which to compare levels of lethal violence observed throughout our history.

Social neuroendocrinology of human aggression: examining the role of competition-induced testosterone dynamics

A large body of evidence indicates that individual differences in baseline concentrations of testosterone (T) are only weakly correlated with human aggression. Importantly, T concentrations are not static, but rather fluctuate rapidly in the context of competitive interactions, suggesting that acute fluctuations in T may be more relevant for our understanding of the neuroendocrine mechanisms underlying variability in human aggression. In this paper, we provide an overview of the literature on T and human competition, with a primary focus on the role of competition-induced T dynamics in the modulation of human aggression. In addition, we discuss potential neural mechanisms underlying the effect of T dynamics on human aggression. Finally, we highlight several challenges for the field of social neuroendocrinology and discuss areas of research that may enhance our understanding of the complex bi-directional relationship between T and human social behavior.

Violated expectancies: Cause and function of exploration, fear, and aggression

To be able to reproduce, animals need to survive and interact with an ever changing environment. Therefore, they create a cognitive representation of that environment, from which they derive expectancies regarding current and future events. These expected events are compared continuously with information gathered through exploration, to guide behaviour and update the existing representation. When a moderate discrepancy between perceived and expected events is detected, exploration is employed to update the internal representation so as to alter the expectancy and make it match the perceived event. When the discrepancy is relatively large, exploration is inhibited, and animals will try to alter the perceived event utilizing aggression or fear. The largest discrepancies are associated with a tendency to flee. When an exploratory, fear, or aggressive behaviour pattern proofs to be the optimal solution for a particular discrepancy, the response will become conditioned to events that previously preceded the occurrence of that discrepancy. When primary needs are relatively low, animals will actively look for or create moderately violated expectancies in order to learn about objects, behaviour patterns, and the environment. In those situations, exploratory tendencies will summate with ongoing behaviour and, when all primary needs are satiated, may even be performed exclusively. This results in behavioural variability, play, and active information-seeking. This article is part of a Special Issue entitled: In Honor of Jerry Hogan.

Neuropsychiatry of aggression

Aggression is a serious medical problem that can place both the patient and the health care provider at risk. Aggression can result from medical, neurologic, and/or psychiatric disorders. A comprehensive patient evaluation is needed. Treatment options include pharmacotherapy as well as nonpharmacologic interventions, both of which need to be individualized to the patient.

Annual Research Review: Prenatal stress and the origins of psychopathology: an evolutionary perspective

If a mother is stressed or anxious while pregnant her child is more likely to show a range of symptoms such as those of attention deficit hyperactivity disorder, conduct disorder, aggression or anxiety. While there remains some debate about what proportion of these effects are due to the prenatal or the postnatal environment, and the role of genetics, there is good evidence that prenatal stress exposure can increase the risk for later psychopathology. Why should this be? In our evolutionary history it is possible that some increase in these characteristics in some individuals was adaptive in a stressful environment, and that this type of fetal programming prepared the child or group for the environment in which they were going to find themselves. Anxiety may have been associated with increased vigilance, distractible attention with more perception of danger, impulsivity with more exploration, conduct disorder with a willingness to break rules, and aggression with the ability to fight intruders or predators. This adaptation for a future dangerous environment may explain why stress and anxiety, rather than depression, seem to have these programming effects; why there is a dose-response relationship with prenatal stress from moderate to severe and it is not only toxic stress that has consequences; why not all children are affected and why individual children are affected in different ways; and why the outcomes affected can depend on the sex of the offspring. An evolutionary perspective may give a different understanding of children in our society with these symptoms, and suggest new directions for research. For example, there is some evidence that the type of cognitive deficits observed after prenatal stress have specific characteristics; these may be those which were adaptive in a past environment.