Individual Differences In Aggression Research Articles

Aggressiveness predicts dominance rank in greylag geese: mirror tests and agonistic interactions.

Individual differences in aggressiveness, if consistent across time and contexts, may contribute to the long-term maintenance of social hierarchies in complex animal societies. Although agonistic interactions have previously been used to calculate individuals' positions within a dominance hierarchy, to date the repeatability of agonistic behaviour has not been tested when calculating social rank. Here, we examined the consistency and social relevance of aggressiveness as a personality trait in a free-flying population of greylag geese (Anser anser). For each individual, we quantified (i) aggressiveness using a standardized mirror stimulation test and (ii) dominance ranking based on the number of agonistic interactions won and lost in a feeding context. We found that individual differences in aggressiveness were significantly repeatable and that individuals' aggressiveness predicted their dominance rank position. The flock showed a robust and intermediately steep dominance hierarchy. Social rank was higher in paired birds, males and older birds, and most agonistic interactions occurred between individuals with moderate rank differences. We suggest that selection favours aggressiveness as a personality trait associated with resource acquisition and social rank, whereby a dominance hierarchy may increase the benefits of group living and reduce costs over conflict within dyads.

Electrodermal lability and overt aggression: Testing the trait-like nature of skin conductance responses

Electrodermal activity (EDA) has been shown to reflect a physiological index of many cognitive processes, such as attention, orientation, and working memory. Crider (2008) has argued that EDA lability may index ability to successfully employ cognitive control so as to down-regulate emotion. We test this model by considering whether EDA lability would relate to emotion-related impulsivity and aggression, as well as cognitive control measured by the antisaccade task in a sample of 221 participants selected for a broad range of internalizing and externalizing syndromes. Baseline EDA was gathered at baseline, and task EDA was gathered during the antisaccade task. Partial correlation models controlled for prosaccade gaze accuracy in considering the association of EDA and antisaccade performance. Emotion-related impulsivity was unrelated to EDA indices. We discuss methodological and conceptual issues with regards to the nonconvergence of psychophysiological (EDA) indices with behavioral and self-report measures, and address challenges in identifying lab-based correlates of longer-term individual differences in aggression or impulsivity.

Continuity of Genetic Risk for Aggressive Behavior Across the Life-Course

We test whether genetic influences that explain individual differences in aggression in early life also explain individual differences across the life-course. In two cohorts from The Netherlands (N = 13,471) and Australia (N = 5628), polygenic scores (PGSs) were computed based on a genome-wide meta-analysis of childhood/adolescence aggression. In a novel analytic approach, we ran a mixed effects model for each age (Netherlands: 12–70 years, Australia: 16–73 years), with observations at the focus age weighted as 1, and decaying weights for ages further away. We call this approach a ‘rolling weights’ model. In The Netherlands, the estimated effect of the PGS was relatively similar from age 12 to age 41, and decreased from age 41–70. In Australia, there was a peak in the effect of the PGS around age 40 years. These results are a first indication from a molecular genetics perspective that genetic influences on aggressive behavior that are expressed in childhood continue to play a role later in life.

Male aggressiveness and risk-taking during reproduction are repeatable but not correlated in a wild bird population

The existence of among-individual variation in behaviour within populations is poorly understood. Recent theory suggests that fine-scale individual differences in investment into current versus future reproduction may lead to a ‘slow-fast’-pace-of-life continuum, also referred to as the ‘pace-of-life-syndrome’ (POLS) hypothesis. According to this idea, individuals are predicted to differ in their level of risk-taking, which may drive among-individual variation and covariation of behaviours. Consistent individual differences in aggression, an ecologically relevant and potentially risky behaviour, have been reported across the animal kingdom. Here we test whether such individual differences in aggression are a manifestation of underlying differences in risk-taking. In a wild blue tit (Cyanistes caeruleus) population, we used standard behavioural tests to investigate if male territorial aggressiveness and risk-taking during breeding are positively related. At the start of breeding, we simulated conspecific territorial intrusions to obtain repeated measures of male aggressiveness. Subsequently, we measured male risk-taking as their latency to resume brood provisioning after presenting two different predators at their nest: human and sparrowhawk, a common predator of adult songbirds. First, we found substantial repeatability for male aggressiveness (R = 0.56 ± 0.08 SE). Second, while males took longer to resume provisioning after presentation of a sparrowhawk mount as compared to a human observer, risk-taking was repeatable across these two predator contexts (R = 0.51 ± 0.13 SE). Finally, we found no evidence for a correlation between male aggressiveness and risk-taking, thereby providing little support to a main prediction of the POLS hypothesis.Significance statementConsistent, and often correlated, individual differences in basal behaviours, such as aggression, exploration and sociability, are found across the animal kingdom. Why individuals consistently differ in their behaviour is poorly understood, as behavioural traits would seem inherently flexible. The ‘pace-of-life syndrome’ (POLS) hypothesis proposes observed behavioural variation to reflect differences in risk-taking associated with individual reproductive strategies. We tested this idea in a wild blue tit population by investigating whether individual males that were more aggressive toward territorial intruders also took more risk when provisioning their nestlings under a threat of predation. While we found consistent individual differences in both aggressiveness and risk-taking, these behaviours were not significantly correlated. Therefore, our study demonstrates among-individual variation in ecologically relevant behaviours in wild blue tits but provides little support for the POLS hypothesis.

Quantitative standardization of resident mouse behavior for studies of aggression and social defeat.

Territorial reactive aggression in mice is used to study the biology of aggression-related behavior and is also a critical component of procedures used to study mood disorders, such as chronic social defeat stress. However, quantifying mouse aggression in a systematic, representative, and easily adoptable way that allows direct comparison between cohorts within or between studies remains a challenge. Here, we propose a structural equation modeling approach to quantify aggression observed during the resident-intruder procedure. Using data for 658 sexually experienced CD-1 male mice generated by three research groups across three institutions over a 10-year period, we developed a higher-order confirmatory factor model wherein the combined contributions of latency to the first attack, number of attack bouts, and average attack duration on each trial day (easily observable metrics that require no specialized equipment) are used to quantify individual differences in aggression. We call our final model the Mouse Aggression Detector (MAD) model. Correlation analyses between MAD model factors estimated from multiple large datasets demonstrate generalizability of this measurement approach, and we further establish the stability of aggression scores across time within cohorts and demonstrate the utility of MAD for selecting aggressors which will generate a susceptible phenotype in social defeat experiments. Thus, this novel aggression scoring technique offers a systematic, high-throughput approach for aggressor selection in chronic social defeat stress studies and a more consistent and accurate study of mouse aggression itself.

Neuromodulatory effect of interleukin 1β in the dorsal raphe nucleus on individual differences in aggression.

Heightened aggressive behavior is considered as one of the central symptoms of many neuropsychiatric disorders including autism, schizophrenia, and dementia. The consequences of aggression pose a heavy burden on patients and their families and clinicians. Unfortunately, we have limited treatment options for aggression and lack mechanistic insight into the causes of aggression needed to inform new efforts in drug discovery and development. Levels of proinflammatory cytokines in the periphery or cerebrospinal fluid were previously reported to correlate with aggressive traits in humans. However, it is still unknown whether cytokines affect brain circuits to modulate aggression. Here, we examined the functional role of interleukin 1β (IL-1β) in mediating individual differences in aggression using a resident-intruder mouse model. We found that nonaggressive mice exhibit higher levels of IL-1β in the dorsal raphe nucleus (DRN), the major source of forebrain serotonin (5-HT), compared to aggressive mice. We then examined the effect of pharmacological antagonism and viral-mediated gene knockdown of the receptors for IL-1 within the DRN and found that both treatments consistently increased aggressive behavior of male mice. Aggressive mice also exhibited higher c-Fos expression in 5-HT neurons in the DRN compared to nonaggressive mice. In line with these findings, deletion of IL-1 receptor in the DRN enhanced c-Fos expression in 5-HT neurons during aggressive encounters, suggesting that modulation of 5-HT neuronal activity by IL-1β signaling in the DRN controls expression of aggressive behavior.

Epigenetics of Aggression.

Aggression is a complex behavioral trait modulated by both genetic and environmental influences on gene expression. By controlling gene expression in a reversible yet potentially lasting manner in response to environmental stimulation, epigenetic mechanisms represent prime candidates in explaining both individual differences in aggression and the development of elevated aggressive behaviors following life adversity. In this manuscript, we review the evidence for an epigenetic basis in the development and expression of aggression in both humans and related preclinical animal models. In particular, we discuss reports linking DNA methylation, histone post-translational modifications, as well as non-coding RNA, to the regulation of a variety of genes implicated in the neurobiology of aggression including neuropeptides, the serotoninergic and dopaminergic systems, and stress response related systems. While clinical reports do reveal interesting patterns of DNA methylation underlying individual differences and experience-induced aggressive behaviors, they do, in general, face the challenge of linking peripheral observations to central nervous system regulations. Preclinical studies, on the other hand, provide detailed mechanistic insights into the epigenetic reprogramming of gene expression following life adversities. Although the functional link to aggression remains unclear in most, these studies together do highlight the involvement of epigenetic events driven by DNA methylation, histone modifications, and non-coding RNA in the neuroadaptations underlying the development and expression of aggression.

Does the tie fit the female? Melanin-based colouration, aggressive personality and reproductive investment in female great tits (Parus major)

The evolution and function of female trait exaggeration in species with traditional sex roles are poorly understood. Competition for social and ecological resources, rather than mating opportunities, may be a key selection pressure in females of socially monogamous species. Moreover, such pre-existing resource competition-selected traits (armaments) may become the object of mating preferences (ornaments); however, the benefits that males may gain in choosing more ornamented females remain unclear. Here, using observational data on free-living female great tits (Parus major), we explore whether tie size, a well-known melanin-pigmented plumage trait, covaries with intrasexual aggressiveness during the breeding season and the investment in current reproduction (fledgling number and mass). We found consistent individual differences (i.e. personality variation) in most of the aggressiveness parameters studied. Moreover, we found support for a signalling role of tie size with respects to how close females approached intruders. Interestingly, this relationship was only evident in older females, not first-year breeding females, suggesting age-related changes in the information content of tie size in the context of same-sex aggressiveness. Additionally, although first-year breeding females, on average, produced fledglings with lower body mass compared to older females, tie size was positively associated with fledgling mass, suggesting that males could potentially gain benefits by choosing females with larger tie size. Experimental studies are now necessary to confirm whether females with larger tie size have a selective advantage in female competition (i.e. armament), as well as whether males base their mate choice on female tie size (i.e. ornament). Why females of many species with traditional sex roles often have exaggerated traits very similar to those found in males remains poorly understood. We explored the functional significance of a well-known melanin-based plumage trait (tie size) in females of a socially monogamous passerine bird, the great tit. Female tie size positively covaried with consistent individual differences in aggressiveness during female-female interactions, but only so in older females and not first-year breeding females. In addition, females with larger tie size produced fledglings with higher body mass, suggesting that it could potentially be used by males in mate choice. Our study emphasizes that greater attention should be paid to female trait exaggeration in socially monogamous species in the context of female-female competition and male mate choice, as well as to potential age-related changes in the information they convey.

Collective responses to heterospecifics emerge from individual differences in aggression.

Variation in individual behavior among group members impacts collective outcomes. The ability of both individuals and groups to outcompete others can determine access to resources. The invasive Argentine ant, Linepithema humile, dominates resources and displaces native species. To determine how access to resources by groups of L. humile is impacted by their behavioral composition, we first determined that L. humile workers consistently vary in aggressive behavior. We then asked if variation in aggression within a group influences the group's ability to access a resource in the presence of cues of a native species, Tapinoma sessile. We found that the behavioral composition of L. humile groups impacted the groups' collective response to cues of T. sessile. Group behavior was the result of mostly additive, rather than synergistic, combinations of the behaviors of the group members. The behavior of groups that contained 50% highly aggressive and 50% low-aggression individuals was similar to the average of the behaviors of groups of all highly aggressive and groups of all low-aggression individuals. Uncovering the mechanisms that allow social invasive species to dominate the ecological communities they invade can inform the mitigation of invasion.

Trait aggressiveness predicting aggressive behavior: The moderating role of meta-cognitive certainty.

Research on aggression has benefitted from using individual-difference measures to predict aggressive behavior. Research on meta-cognition has recently identified that the predictive utility of individual-difference inventories can be improved by considering the certainty with which people hold their self-views. Merging these two frameworks, the present research examines whether assessing certainty in trait aggressiveness improves its ability to predict aggressive outcomes. Across two studies, participants reported their level of trait physical aggressiveness and the certainty with which they held their responses to the scale (predictor variables). Aggressive behavioral intentions (Study 1 and 2) and actual aggressive behavior (Study 2) were used as dependent measures. As hypothesized, results indicated that certainty moderated the effects of individual-differences in aggressiveness on both aggressive outcomes. Therefore, considering the certainty with which people hold their relevant traits can be useful for understanding aggression, and also for predicting the consistency between personality and behavior.

The relationship between physical aggression, foreign policy and moral choices: Phenotypic and genetic findings.

Previous work has demonstrated that both leaders and other individuals vary in dispositional levels of physical aggression, which are genetically influenced. Yet the importance of individual differences in aggression for attitudes toward foreign policy or context-laden moral choices, such as sacrificing the lives of some for the greater good of many, has yet to be fully explored. Given the global importance of such decisions, we undertook this exploration in a sample of 586 Australians, including 250 complete twin pairs. We found that individuals who scored higher on Buss-Perry's physical aggression scale were more likely to support aggressive foreign policy interventions and displayed a more utilitarian moral calculus than those who scored lower on this scale. Furthermore, we found that the majority of variance in physical aggression lay in genetic factors for men, whereas the majority of the variance was in environmental factors for women. The source of covariation between aggression and political choices also differed between the sexes. A combination of genetic and environmental factors accounted for most of the cross-trait correlations among males, whereas common and unique environmental factors accounted for most of the cross-trait correlations among females. We consider the implications of our results for understanding how trait measures of aggression are associated with foreign policy and moral choices, providing evidence for why and how individuals differ in responding to complex social dilemmas. Aggr. Behav. 43:37-46, 2017. © 2016 Wiley Periodicals, Inc.

Do Anger Control and Social Problem-Solving Mediate Relationships Between Difficulties in Emotion Regulation and Aggression in Adolescents?

Emotions are an individual's reaction to their environment to either maintain or change the environment (Saarni, Mumme, & Campos, 1998) and provide individuals with very useful knowledge about themselves, their environment, and their relationships (Zeman, Cassano, Perry-Parrish, & Stegall, 2006). Emotion regulation is the ability to modify and adapt emotions to the social context (Campos, Mumme, Kermoian, & Campos, 1994). It is described as the intrinsic and extrinsic processes responsible for observing, assessing, and modulating emotional responses for personal purpose and adaptive social functioning (Thompson, 1994). Studies indicated that effective emotion regulation is connected with fewer internalizing and externalizing issues (Rydell, Thorell, & Bohlin, 2007), while ineffective emotion regulation is associated with mental health problems (Gross & John, 2003).The skill to communicate one's emotional experiences to another person develops during late childhood and adolescence (Kopp, 1992). Adolescents experience more frequent and stronger emotions than both younger and older people (Larson & Lampman-Petraitis, 1989). It is important for adolescents to regulate emotions in adaptive ways, without the assistance of the adults who guide them in their childhood (Steinberg & Avenevoli, 2000). Adolescents who were less capable of regulating negative feelings during actual-life emotional experiences mentioned more problems compared with those who handled negative experiences more readily (Silk, Steinberg, & Morris, 2003). In particular, poor emotional understanding and difficulties in regulating negative emotions has been linked to aggression in adolescence (Bohnert, Crnic, & Lim, 2003; Herts, McLaughlin, & Hatzenbuehler, 2012).Indeed, adolescents who are capable of managing their emotional behavior are less likely to act aggressively (Underwood, Coie, & Herbsman, 1992). However, those with great difficulties in emotion regulation had problems with anger control and aggressive behavior (McLaughlin, Hatzenbuehler, Mennin, & Nolen-Hoeksema, 2011). However, only a few studies have researched the relationship between aggression and difficulties in emotion regulation (Laible, Carlo, Panfile, Eye, & Parker, 2010). Because most of the evidence on this topic comes from results that have indicated a relationship between anger control and aggression (Roberton, Daffern, & Bucks, 2012), a better comprehension of difficulties in emotion regulation during adolescence can identify individual differences in aggression at the time of increased risk (Silk, Steinberg, & Morris, 2003).Aggressive behavior is predicted by anger in adolescents. Anger leads to adolescent to misinterpret existing cues, and this misinterpretation is more likely results in physical, verbal, and indirect aggression (Fives, Kong, Fuller, & DiGiuseppe, 2010). The cognitive contents specificity model, the most commonly discussed model, suggests that increased anger results in socially constructed apparent behavioral reactions in the shape of aggression, and these reactions mainly function to remove the anger (Kassinove & Tafrate, 2002). At the same time, research shows that aggressive behavior does not decrease the level of experienced anger. Indeed, conversely, research indicates that discharging aggressive behavior (i.e., kicking a punch-bag) makes the anger worse (Bushman, 2002).It is claimed that individuals with increased anger may become angry because of a lack of emotion regulation ability and, in turn, perpetrate aggression (Harper, Austin, Cercone, & Arias, 2005). Difficulties in emotion regulation are associated with increased anger (Wilkinson & Robinson, 2008) and decreased anger control (McLaughlin et al., 2011), suggesting that a failure to control one's emotions might cause increased anger and then aggression. An understanding of one's own emotions is important for the appropriate expression and management of emotional experiences (Saarni, Mumme, & Campos, 1998). …

Effects of oxytocin on aggressive responding in healthy adult men.

This study investigated the acute effects of oxytocin (OT) on human aggression using a well-established laboratory measure of state (reactive) aggression to test the hypothesis that OT would decrease the frequency of aggressive responding. In a within-subject design, 17 healthy male volunteers received placebo or 24 IU of intranasal OT. Aggression was measured using the Point Subtraction Aggression Paradigm at 30 min before and 30, 60, and 90 min after dose. Acute OT did not produce a significant main effect on aggressive behavior. OT attenuated the expected rise in diastolic blood pressure from morning to early afternoon observed under placebo, providing a possible indication of biological activity. Examination of individual differences showed that aggressive responding following OT dosing (but not placebo) was positively correlated with psychometric measures of interpersonal manipulation and anger (Pearson's r=0.57), indicating that higher scores on these antisocial personality traits were related to increased aggressive behavior following OT administration. These preliminary results stand in contrast to previous work on the prosocial effects of OT and highlight the need for further understanding of individual differences in aggression following OT administration. Such individual differences may have implications for the therapeutic use of OT in individuals with psychiatric disorders and dysfunctional social behavior.

Mapping of Genetic Factors That Elicit Intermale Aggressive Behavior on Mouse Chromosome 15: Intruder Effects and the Complex Genetic Basis.

Despite high estimates of the heritability of aggressiveness, the genetic basis for individual differences in aggression remains unclear. Previously, we showed that the wild-derived mouse strain MSM/Ms (MSM) exhibits highly aggressive behaviors, and identified chromosome 15 (Chr 15) as the location of one of the genetic factors behind this escalated aggression by using a panel of consomic strains of MSM in a C57BL/6J (B6) background. To understand the genetic effect of Chr 15 derived from MSM in detail, this study examined the aggressive behavior of a Chr 15 consomic strain towards different types of opponent. Our results showed that both resident and intruder animals had to have the same MSM Chr 15 genotype in order for attack bites to increase and attack latency to be reduced, whereas there was an intruder effect of MSM Chr 15 on tail rattle behavior. To narrow down the region that contains the genetic loci involved in the aggression-eliciting effects on Chr 15, we established a panel of subconsomic strains of MSM Chr 15. Analysis of these strains suggested the existence of multiple genes that enhance and suppress aggressive behavior on Chr 15, and these loci interact in a complex way. Regression analysis successfully identified four genetic loci on Chr 15 that influence attack latency, and one genetic locus that partially elicits aggressive behaviors was narrowed down to a 4.1-Mbp region (from 68.40 Mb to 72.50 Mb) on Chr 15.

Intranasally administered oxytocin affects how dogs (Canis familiaris) react to the threatening approach of their owner and an unfamiliar experimenter

Fear and aggression are among the most prominent behavioural problems in dogs. Oxytocin has been shown to play a role in regulating social behaviours in humans including fear and aggression. As intranasal oxytocin has been found to have some analogous effects in dogs and humans, here we investigated the effect of oxytocin on dogsʼ behaviour in the Threatening Approach Test. Dogs, after having received intranasal administration of oxytocin (OT) or placebo (PL), showed the same reaction to an unfamiliar experimenter, but OT pretreated dogs showed a less friendly first reaction compared to the PL group when the owner was approaching. Individual differences in aggression (measured via questionnaire) also modulated dogs’ first reaction. Moreover, subjects that received OT looked back more at the human (owner/experimenter) standing behind them during the threatening approach. These results suggest that oxytocin has an effect on dogsʼ response to the threatening cues of a human, but this effect is in interaction with other factors such as the identity of the approaching human and the ‘baseline’ aggression of the dogs.

The girls set the tone: gendered classroom norms and the development of aggression in adolescence.

In a four-wave longitudinal study with N = 1,321 adolescents in Germany, we examined the impact of class-level normative beliefs about aggression on aggressive norms and behavior at the individual level over the course of 3 years. At each data wave, participants indicated their normative acceptance of aggressive behavior and provided self-reports of physical and relational aggression. Multilevel analyses revealed significant cross-level interactions between class-level and individual-level normative beliefs at T1 on individual differences in physical aggression at T2, and the indirect interactive effects were significant up to T4. Normative approval of aggression at the class level, especially girls' normative beliefs, defined the boundary conditions for the expression of individual differences in aggressive norms and their impact on physically and relationally aggressive behavior for both girls and boys. The findings demonstrate the moderating effect of social norms on the pathways from individual normative beliefs to aggressive behavior in adolescence.

Aggressive priming online: Facebook adverts can prime aggressive cognitions

Through the process of priming, incidental stimuli in our environments can influence our thoughts, feelings and behaviour. This may be true of incidental stimuli in online environments, such as adverts on websites. Two experiments (N=325, N=331) showed that the mere presence of advertisements with violent content on a simulated Facebook page induced higher levels of aggression-related cognition in comparison to non-violent adverts (d=0.56, d=0.71). In a subsequent word recognition task, participants primed with the violent stimuli ‘remembered’ more actually-unseen violence-related words than did the control participants. That is, they reported recognising violent words they had not actually seen. However, priming with violent adverts had no effect on mood or person perception. A third correlational study (N=131) examined whether variance in the extent of priming could be attributed to individual differences in aggressiveness. Participants’ aggressiveness was unrelated to their scores on the aggressive cognition measure. These studies established that website adverts with violent content could prime aggressive cognitions. Individuals differed in the extent to which they experienced the priming effect, and this was not attributable to their levels of trait aggressiveness. No effects of priming were found on either mood state or person perception.

Child exposure to serious life events, COMT, and aggression: Testing differential susceptibility theory.

Both genetic and environmental factors contribute to individual differences in aggression. Catechol-O-methyltransferase Val158Met (COMT), a common, functional polymorphism, has been implicated in aggression and aggression traits, as have childhood experiences of adversity. It is unknown whether these effects are additive or interactional and, in the case of interaction, whether they conform to a diathesis-stress or differential susceptibility model. We examined Gene × Environment interactions between COMT and serious life events on measures of childhood aggression and contrasted these 2 models. The sample was composed of community children (N = 704); 355 were boys, and the mean age was 54.8 months (SD = 3.0). The children were genotyped for COMT rs4680 and assessed for serious life events and by teacher-rated aggression. Regression analysis showed no main effects of COMT and serious life events on aggression. However, a significant interactive effect of childhood serious life events and COMT genotype was observed: Children who had faced many serious life events and were Val homozygotes exhibited more aggression (p = .02) than did their Met-carrying counterparts. Notably, in the absence of serious life events, Val homozygotes displayed significantly lower aggression scores than did Met carriers (p = .03). When tested, this constellation of findings conformed to the differential susceptibility hypothesis: In this case, Val homozygotes are more malleable to the effect of serious life events on aggression and not simply more vulnerable to the negative effect of having experienced many serious life events.

Sugar levels relate to aggression in couples without supporting the glucose model of self-control.

Sugar levels relate to aggression in couples without supporting the glucose model of self-control.

An actor—Partner interdependence model of the Dark Triad and aggression in couples

The Dark Triad traits—Machiavellianism, psychopathy, and narcissism—form a set of personality strategies that serve to exploit and manipulate others. Although the Dark Triad traits and their correlates have been studied in individuals, little is known about their role in young adult couples in dating relationships, or how these traits relate to individual differences in aggression. To these ends, we had 44 heterosexual dating undergraduate couples (88 participants) self-report trait measures of the Dark Triad Dirty Dozen (Jonason & Webster, 2010) and measures of direct and displaced trait aggression. Using a series of actor–partner interdependence models showed that men’s psychopathy positively related to women’s hostility and physical aggression. Women’s psychopathy positively related to their own verbal and displaced aggression, and men’s anger rumination. Men’s Machiavellianism positively related to women’s displaced aggression. Men’s narcissism positively related to their own revenge planning. We discuss possible implications for intimate partner violence.