Sex Differences In Physical Aggression Research Articles

Sex differences in early experience and the development of aggression in wild chimpanzees

Sex differences in physical aggression occur across human cultures and are thought to be influenced by active sex role reinforcement. However, sex differences in aggression also exist in our close evolutionary relatives, chimpanzees, who do not engage in active teaching, but do exhibit long juvenile periods and complex social systems that allow differential experience to shape behavior. Here we ask whether early life exposure to aggression is sexually dimorphic in wild chimpanzees and, if so, whether other aspects of early sociality contribute to this difference. Using 13 y of all-occurrence aggression data collected from the Kanyawara community of chimpanzees (2005 to 2017), we determined that young male chimpanzees were victims of aggression more often than females by between 4 and 5 (i.e., early in juvenility). Combining long-term aggression data with data from a targeted study of social development (2015 to 2017), we found that two potential risk factors for aggression-time spent near adult males and time spent away from mothers-did not differ between young males and females. Instead, the major risk factor for receiving aggression was the amount of aggression that young chimpanzees displayed, which was higher for males than females throughout the juvenile period. In multivariate models, sex did not mediate this relationship, suggesting that other chimpanzees did not target young males specifically, but instead responded to individual behavior that differed by sex. Thus, social experience differed by sex even in the absence of explicit gender socialization, but experiential differences were shaped by early-emerging sex differences in behavior.

Sex differences in adolescent physical aggression: Evidence from sixty-three low-and middle-income countries.

A great deal of research shows that adolescent and adult males are more likely to engage in physical aggression and violence than females are. However, few studies have examined cross‐cultural variation in sex differences, particularly among low‐ and middle‐income countries [LMICs]. Based on social role and sexual selection theories, we derived two hypotheses regarding possible variations in sex differences across societal contexts: 1) sex differences increase with societal gender polarization (social role theory) and 2) sex differences are exacerbated in societies where socio‐economic opportunities are scarce, unequal, or insecure (prediction derived from sexual selection theory). The current study examined the prevalence of and variation in sex differences in physical aggression, as measured by frequent fighting, among 247,909 adolescents in 63 low‐ and middle‐income countries. The results show that, overall, males were over twice as likely (OR = 2.68; 95% CI = 2.60–2.76) to report frequent fighting in the past 12 months than females. However, sex differences vary significantly across LMICs, wherein countries with higher female prevalence rates have smaller sex differences in frequent fighting. Contrary to expectations derived from social role theory, sex differences in physical aggression decrease as societal gender inequality increased. In regards to sexual selection theory, we find no evidence that sex differences in frequent fighting varies according to societal rule of law or income inequality.

The impact of parenthood on physical aggression: Evidence from criminal data.

Evolutionary approaches to sex differences in physical aggression weigh the potential benefits of aggression against the likely costs to inclusive fitness, with some authors focusing on the damage physical injury would do to female inclusive fitness, and others on the extent to which success in physical competition may particularly enhance male fitness. This study tested a hypothesis derived from these approaches: that parents would be less physically aggressive than non-parents because of the damage any physical injury would do to their inclusive fitness. Analysis was carried out using the United States federal sentencing records for 1994-1999 (22,344 individuals). The proportion of theft convictions which were violent (robbery; vs. larceny) was significantly greater for men than women (odds ratio 7.7). As predicted, non-parents were significantly more likely to be violent than parents (odds ratio 1.6). Parenthood had a similar effect on relative rates of violence in men and women, although the baseline was considerably higher for men. There was also a significant effect in men of marital status, which interacted with parental status such that parenthood was only associated with a reduction in rates of violence in males recorded as partnered. The results are interpreted in terms of both evolutionary theory and recent work on the hormonal impacts of marriage and parenthood. Aggr. Behav. 42:577-584, 2016. © 2016 Wiley Periodicals, Inc.

Interpersonal Aggression among Aka Hunter-Gatherers of the Central African Republic

Sex differences in physical and indirect aggression have been found in many societies but, to our knowledge, have not been studied in a population of hunter-gatherers. Among Aka foragers of the Central African Republic we tested whether males physically aggressed more than females, and whether females indirectly aggressed more than males, as has been seen in other societies. We also tested predictions of an evolutionary theory of physical strength, anger, and physical aggression. We found a large male bias in physical aggression. Controlling for anger, we found an adult female bias in indirect aggression. Physical strength predicted anger, which predicted hitting, although results were sensitive to the inclusion or exclusion of traditional healers, who were physically and emotionally distinct from other Aka. With some important caveats, our results generally support the predicted sex differences in physical aggression and indirect aggression, and the predicted relationships among anger, strength, and aggression.

Are there sex differences in physical aggression in the elderly?

Sexual selection theory proposes that sex differences in physical aggression are due to greater male than female competition for reproduction which leads males to use more risky strategies. This difference seems to peak around 20–30 years old, which is consistent with this theory. Nevertheless, no studies have focused on sex differences in aggression in the elderly. The present study explores sex differences in aggression in an elderly sample (aged 65–96). Results showed that although sex differences in physical aggression were present, the effect size was small and lower than the effect sizes obtained in younger samples. Furthermore, women showed higher levels of anger. Although the results seem to fit with sexual selection theory, they will have to be confirmed by future studies in new cohorts.

Development of sex differences in physical aggression: The maternal link to epigenetic mechanisms

AbstractAs Archer argues, recent developmental data on human physical aggression support the sexual selection hypothesis. However, sex differences are largely due to males on a chronic trajectory of aggression. Maternal characteristics of these males suggest that, in societies with low levels of physical violence, females with a history of behavior problems largely contribute to maintenance of physical aggression sex differences.

Does Relational Aggression Clarify or Confuse the Study of Sex Differences in Aggression?

Dr. Cote provides an interesting review of the development of sex differences in physical and non-physical aggression and begins to propose mechanisms by which such sex differences emerge including biological, evolutionary, and social factors. Until recently, the finding that significant sex differences exist in the prevalence of different forms of psychopathology was underutilized in etiological research. Fortunately, there has been a bit of a paradigm shift such that understanding sex differences is now a main aim of many studies, and one that has even drawn support from funding agencies such as the National Institute of Health in the US. The study of sex differences in aggression has been greatly influenced by the emergence of the constructs indirect aggression, social aggression and relational aggression, which are relatively synonymous. Before one can build a developmental model of aggression that has, at its premise, the assumption that boys are more likely to engage in physical aggression and girls are more likely to engage in relational aggression, at least two issues need to be resolved. The first is whether relational aggression occurs more frequently in girls than in boys. Although there may be some debate, as evident in Dr. Cote’s review as to the point in development when reliable sex differences in physical aggression emerge, there is very strong evidence that such sex differences are consistently found beginning at some point in the first 4–5 years of life and that they increase in magnitude with age. Data are not as consistent in revealing sex differences in relational aggression. In some studies girls are reported to be more relationally aggressive (e.g., Crick and Grotpeter 1995), whereas in other studies boys are reported to exhibit higher levels of relational aggression than girls (e.g., McEvoy et al. 2003; Tomada and Schneider 1997). In still other studies, the association between relational aggression and impairment has been stronger for boys than for girls (Crick Eur J Crim Policy Res (2007) 13:201–203 DOI 10.1007/s10610-007-9047-2

Sex differences in aggression between heterosexual partners: a meta-analytic review.

Meta-analyses of sex differences in physical aggression to heterosexual partners and in its physical consequences are reported. Women were slightly more likely (d = -.05) than men to use one or more act of physical aggression and to use such acts more frequently. Men were more likely (d = .15) to inflict an injury, and overall, 62% of those injured by a partner were women. The findings partially support previous claims that different methods of measurement produce conflicting results, but there was also evidence that the sample was an important moderator of effect size. Continuous models showed that younger aged dating samples and a lower proportion of physically aggressive males predicted effect sizes in the female direction. Analyses were limited by the available database, which is biased toward young dating samples in the United States. Wider variations are discussed in terms of two conflicting norms about physical aggression to partners that operate to different degrees in different cultures.

Sex differences in physical aggression to partners: A reply to Frieze (2000), O'Leary (2000), and White, Smith, Koss, and Figueredo (2000).

Sex differences in physical aggression to partners: A reply to Frieze (2000), O'Leary (2000), and White, Smith, Koss, and Figueredo (2000).

Verbal aggression as a function of sex of subject and sex of target.

This experiment raised the question of whether previously reported sex differences in physical aggression also hold for verbal aggression. It was hypothesized that verbal aggression would be a function of sex of the object of aggression but not of the sex of the aggressor. Eighty male and female American college students gave messages which varied in degree of hostile content to either a male or female confederate (C). As predicted, verbral aggression was a function of sex of target but not of S. Verbal aggression was inhibited only toward the female C when the S was not provoked by the C; when provoked, however, Ss displayed the same level of verbal aggression toward female and male targets.