Environmental enrichment can have complex, contradictory effects on aggression and animal welfare. Although increasing enrichment may reduce aggression by limiting the visibility of competitors, it may also intensify territorial defence and harm the welfare of subordinates who are the target of territorial aggression. However, it remains unclear how variation in the complexity of an enrichment structure defended by a single dominant individual influences welfare outcomes for subordinates. In the cichlid fish Astatotilapia burtoni, dominant males defend structures as mating territories, whereas subordinate males do not. To establish social hierarchies, we housed two differently sized males (larger become dominant) and six females in one compartment containing one defendable structure. We manipulated structure complexity by placing 1, 2, or 3 halves of terracotta pots clumped together. Increasing cave number did not enhance territoriality: dominant males showed similar aggression rates, relative gonad sizes, and testosterone levels across treatments. Cave number did not significantly affect mortality, body condition, growth rate, or fin damage in subordinate males. Status-specific behaviours were also not affected by cave number. Although relative gonad size and testosterone levels were generally higher in dominants, these differences were not always significant in the 2- and/or 3-cave treatments, suggesting weaker physiological differentiation between social states. Overall, increasing environmental enrichment had little effect on welfare, but might result in reduced physiological distinctions between dominant and subordinate males. Therefore, careful consideration of enrichment strategies is essential for accurately interpreting status-specific outcomes in laboratory settings.

Aggressive behavior, shaped by genetics and environmental or contextual influences, is expressed differently across development and may lead to criminal justice involvement through arrests and incarceration for some individuals. This study examined the differential impacts of early childhood contextual risk and polygenic risk on a developmental cascade from middle childhood physical aggression and dysregulation to adolescent antisocial behavior, to criminal justice system involvement by age 19, and whether these risks were mitigated by random assignment to the Family Check-Up (FCU) prevention program. The sample included high-risk toddler (N = 731; Mage = 28.2 months, SD = 3.28; 49.5% female, 50% White, 28% Black, 13% Hispanic) and parent dyads involved in a randomized-controlled trial of the FCU and followed longitudinally across 11 waves from ages 2 to 19. Results supported a developmental cascade from middle childhood physical aggression (parent reported) to self-reported legal system involvement at age 19. Early cumulative contextual risk predicted arrests (b = 0.35, p = .001), while a risk tolerance polygenic score predicted self-reported adolescent antisocial behavior (b = 0.51, p = .005). Further, the FCU attenuated the genetic effects on antisocial behavior in adolescence. Findings highlight the value of early prevention for reducing the impact of genetic and contextual risk on rates of justice system involvement by young adulthood.

Resource-guarding behaviour is common in companion dogs and negatively impacts human safety, canine welfare, and the human-canine bond. Experiences with resources during critical sensitive periods of development have the potential to influence adult behaviour around resources. Dog breeder management of puppies’ access to resources (e.g. milk, food, and toys) is largely unknown. In this study, dog breeders in Canada and the US (n = 293) were recruited through convenience sampling to complete a cross-sectional survey on breeding and resource management practices and their puppies’ behaviour around resources. Descriptive statistics and logistic regression models were used to determine how resources were managed, the association between management practices and reported competitive behaviour around resources, and the use of aversive-based training methods. Breeder introduction and type of food and toys provided to puppies varied greatly. Most breeders reported intervening during suckling, feeding, and playing to ensure access to resources and habituating puppies to sensory stimuli. Factors associated with increased odds of reported competitive behaviour around food included breeder intervention during suckling and eating, country and breed. Increased odds of reported competitive behaviour around toys was associated with food competition, breeder intervention during play, puppy toy preferences, and whether littermates played together. Increased odds of the use of aversive-based training methods was associated with puppy competitive behaviour during suckling, eating, and playing. This research highlights the need for longitudinal studies on the development of competitive behaviour from birth to sexual maturity and optimal puppy resource management for the prevention of unwanted behaviours in adulthood.

Drawing on the “social misfit” hypothesis, this study tested whether peer victimization is more predictive of maladjustment when children have many same-race classmates who they view as low in aggression. Also accounted for were children’s race, the racial composition of the classroom, and children’s perceptions of other-race peers. Data were collected in the fall, winter, and spring of a school year from 1,424 4th and 5th grade children (Mage = 10.06; SDage = 0.67; Rangeage = 8.43–13.03; 683 girls; 741 boys; 39.61% Black; 60.39% White) in the Southeastern United States. Measures included children’s ratings of the aggressiveness of their participating Black and White classmates; teacher-reports of depressive symptoms, anxiety, and social withdrawal; and peer-reports of peer victimization, aggression, and prosocial behavior. Consistent with the social misfit hypothesis, when children viewed same-race classmates as low in aggression, peer victimization was more strongly associated with internalizing problems in the fall for Black children (R2: 0.05–0.16) and with heightened anxiety in the spring for White children with many same-race classmates (R2 = 0.09). Although some protective effects of viewing other-race classmates as aggressive emerged, associations with heightened anxiety (R2: 0.06–0.09) underscored the need to promote positive interracial relationships to optimize children’s mental health.

Research on the joint role of testosterone and cortisol in aggression has produced inconsistent results, with limited attention to adolescence, a stage characterized by considerable hormonal changes, and to the distinction between within-and between-person effects. This study examined whether peer victimization moderates testosterone–cortisol associations with bullying perpetration in adolescents. Assessed at three 3-month intervals, participants (471 adolescents, Mage = 14.97, SD = 0.70; 47.1% female) reported bullying perpetration and victimization and provided saliva samples for the analysis of hormones. Random-intercept cross-lagged panel models revealed a three-way interaction (testosterone × cortisol × victimization). Increases in testosterone predicted changes in bullying perpetration when cortisol decreased. These effects were moderated by victimization. When victimization was below average, testosterone increases predicted more bullying perpetration; when it was above average, testosterone increases predicted less perpetration. These findings highlight that peer victimization shapes how testosterone–cortisol interactions influence adolescent aggression, underscoring the interplay of biological and contextual factors in adolescent adaptation.

The study is the first to examine the effects of children’s and therapists’ in-session behaviors on later therapeutic alliance (TA; i.e., relational bond, task collaboration) as rated by children and therapists in an intervention for children with aggressive behavior. One hundred eighty children (ages 9.3–11.8; 69% male; 78% Black), screened as having aggressive behavior by teacher and parent ratings, received a 32-session group-based cognitive-behavioral intervention (Coping Power) at their schools. TA ratings were collected from children and therapists at mid- and end-of-intervention using the Therapeutic Alliance Scale for Children. Children’s and therapists’ behaviors during the first 16 sessions were coded by independent observers. Children’s negative in-session behaviors predicted lower child- and therapist-rated TA (averaged across mid- and end-of-intervention). Children’s in-session positive behaviors, at both the individual and group-wide level, predicted higher later TA. Therapists’ efforts to manage deviant behavior predicted stronger child-reported ratings of the relational bond and of child- and therapist-rated task collaboration. Exploratory analyses indicate that the effect of children’s in-session behaviors on later TA is moderated by therapists’ skills in managing the group and in managing deviant talk and behavior in sessions. Clinical and research implications of the findings are discussed.

Foreign national courts are categorically prohibited from prosecuting a head of state of another country. From the beginning of the twenty-first century until very recently, this view was nearly unanimous. A 2002 decision of the International Court of Justice, in the Arrest Warrant case, strongly supports it. According to the court, heads of state enjoy ‘full immunity’ from foreign criminal jurisdiction. Thus, the prohibition to prosecute foreign heads of state even extends to those who perpetrate aggression and other war-related crimes. That view is based on a twenty-first century myth. According to the myth, heads of state have long – ‘from time immemorial’ – enjoyed an absolute personal immunity from foreign jurisdiction. This article identifies the origin of the myth and parses through crucial historical facts that disprove it, particularly, the indictments against Hitler as the sitting head of state of Germany, their endorsement by the United Nations War Crimes Commission, and the judgment of the International Military Tribunal. A proper debunking of this myth is not only important as a matter of setting the historical record straight but is also relevant for present-day debates about the prosecution of heads of state (or heads of government) who – like Vladimir Putin, Bashar al-Assad, Min Aung Hlaing, and Benjamin Netanyahu – might be responsible for aggression, genocide, war crimes, crimes against humanity, and other crimes.