Editing Aggression (section)

==Evolutionary explanations==
Like many behaviors, aggression can be examined in terms of its ability to help an animal itself survive and reproduce, or alternatively to risk survival and reproduction. This [[cost–benefit analysis]] can be looked at in terms of [[evolution]]. However, there are profound differences in the extent of acceptance of a biological or evolutionary basis for human aggression.<ref>{{cite journal |doi=10.1177/0022002790034003008 |jstor=174228 |title=Humans, Chimps, and Bonobos: The Biological Bases of Aggression, War, and Peacemaking |journal=Journal of Conflict Resolution |volume=34 |issue=3 |pages=553–82 |year=1990 |last1=Somit |first1=A. |s2cid=145380530 }}</ref>

According to the [[male warrior hypothesis]], intergroup aggression represents an opportunity for men to gain access to mates, territory, resources and increased status. As such, conflicts may have created selection evolutionary pressures for psychological mechanisms in men to initiate intergroup aggression.<ref name=":1">{{cite journal |doi=10.1098/rstb.2011.0301 |pmid=22271783 |pmc=3260849 |jstor=41433544 |title=Evolution and the psychology of intergroup conflict: The male warrior hypothesis |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |volume=367 |issue=1589 |pages=670–9 |year=2012 |last1=McDonald |first1=M. M. |last2=Navarrete |first2=C. D. |last3=Van Vugt |first3=M. }}</ref><ref name=":2">{{cite journal |doi=10.1111/j.1467-9280.2007.01842.x |pmid=17362372 |title=Gender Differences in Cooperation and Competition |journal=Psychological Science |volume=18 |issue=1 |pages=19–23 |year=2007 |last1=Vugt |first1=Mark Van |last2=Cremer |first2=David De |last3=Janssen |first3=Dirk P. |citeseerx=10.1.1.518.3529 |s2cid=3566509 }}</ref>

===Violence and conflict===
Aggression can involve [[violence]] that may be [[Adaptation|adaptive]] under certain circumstances in terms of [[natural selection]]. This is most obviously the case in terms of attacking prey to obtain food, or in anti-predatory defense. It may also be the case in competition between members of the same species or subgroup, if the average reward (e.g., status, access to resources, protection of self or kin) outweighs average costs (e.g., injury, exclusion from the group, death). There are some hypotheses of specific adaptions for violence in humans under certain circumstances, including for [[homicide]], but it is often unclear what behaviors may have been selected for and what may have been a byproduct, as in the case of collective violence.<ref>Buss, D.M. (2005). ''[https://books.google.com/books/about/The_Murderer_Next_Door.html?id=NEq9TTBbt64C The murderer next door: Why the mind Is designed to kill]''. New York: Penguin Press.</ref><ref>{{cite journal |doi=10.1016/j.avb.2007.04.001 |title=Examining the evidence from small-scale societies and early prehistory and implications for modern theories of aggression and violence |journal=Aggression and Violent Behavior |volume=13 |issue=1 |pages=1–9 |year=2008 |last1=McCall |first1=Grant S. |last2=Shields |first2=Nancy }}</ref><ref>{{cite book |last1=Buss |first1=D. M. |last2=Duntley |first2=J. D. |chapter-url=http://psycnet.apa.org/psycinfo/2006-20303-012 |chapter=The evolution of aggression |year=2006 |editor1-first=M. |editor1-last=Schaller |editor2-first=J. A. |editor2-last=Simpson |editor3-first=D. T. |editor3-last=Kenrick |title=Evolution and Social Psychology |pages=263–86 |location=New York |publisher=Psychology Press }}</ref><ref>{{cite journal |doi=10.1016/j.avb.2011.04.014 |title=Collective violence: An evolutionary perspective |journal=Aggression and Violent Behavior |volume=16 |issue=5 |pages=428–36 |year=2011 |last1=Durrant |first1=Russil }}</ref>

Although aggressive encounters are ubiquitous in the animal kingdom, with often high stakes, most encounters that involve aggression may be resolved through posturing, or displaying and trial of strength. [[Game theory]] is used to understand how such behaviors might spread by [[natural selection]] within a population, and potentially become 'Evolutionary Stable Strategies'. An initial model of resolution of conflicts is the [[hawk-dove game]]. Others include the [[Risk management|Sequential assessment model]] and the [[Attrition warfare|Energetic war of attrition]]. These try to understand not just one-off encounters but protracted stand-offs, and mainly differ in the criteria by which an individual decides to give up rather than risk loss and harm in physical conflict (such as through estimates of [[resource holding potential]]).<ref>{{cite journal |last1=Briffa |first1=Mark |year=2010 |url=http://www.nature.com/scitable/knowledge/library/territoriality–and–aggression–13240908 |title=Territoriality and Aggression |journal=Nature Education Knowledge |volume=3 |issue=10 |pages=81 }}</ref>

===Gender===
{{Sex differences}}

====General====
Gender plays an important role in human aggression. There are multiple theories that seek to explain findings that males and females of the same species can have differing aggressive behaviors. One review concluded that male aggression tended to produce pain or physical injury whereas female aggression tended towards psychological or social harm.<ref name=pmid3797558>{{cite journal |doi=10.1037/0033-2909.100.3.309 |pmid=3797558 |title=Gender and aggressive behavior: A meta-analytic review of the social psychological literature |journal=Psychological Bulletin |volume=100 |issue=3 |pages=309–30 |year=1986 |last1=Eagly |first1=Alice H. |last2=Steffen |first2=Valerie J. }}</ref>

In general, [[sexual dimorphism]] can be attributed to greater [[intraspecific competition]] in one sex, either between rivals for access to mates and/or to be [[mate choice|chosen by mates]]. This may stem from the other gender being constrained by providing greater [[parental investment]], in terms of factors such as [[gamete]] production, [[gestation]], [[lactation]], or upbringing of young. Although there is much variation in species, generally the more physically aggressive sex is the male, particularly in mammals. In species where parental care by both sexes is required, there tends to be less of a difference. When the female can leave the male to care for the offspring, then females may be the larger and more physically aggressive. Competitiveness despite parental investment has also been observed in some species.<ref>{{cite journal |doi=10.1038/nature05386 |pmid=17183322 |title=Intrasexual competition and sexual selection in cooperative mammals |journal=Nature |volume=444 |issue=7122 |pages=1065–8 |year=2006 |last1=Clutton-Brock |first1=T. H. |last2=Hodge |first2=S. J. |last3=Spong |first3=G. |last4=Russell |first4=A. F. |last5=Jordan |first5=N. R. |last6=Bennett |first6=N. C. |last7=Sharpe |first7=L. L. |last8=Manser |first8=M. B. |bibcode=2006Natur.444.1065C |s2cid=4397323 }}</ref> A related factor is the rate at which males and females are able to mate again after producing offspring, and the basic principles of [[sexual selection]] are also influenced by ecological factors affecting the ways or extent to which one sex can compete for the other. The role of such factors in human evolution is controversial.

The pattern of male and female aggression is argued to be consistent with evolved sexually-selected behavioral differences, while alternative or complementary views emphasize conventional [[gender role|social roles]] stemming from physical evolved differences.<ref>{{cite journal |doi=10.1017/S0140525X09990951 |pmid=19691899 |title=Does sexual selection explain human sex differences in aggression? |journal=Behavioral and Brain Sciences |volume=32 |issue=3–4 |pages=249–66; discussion 266–311 |year=2009 |last1=Archer |first1=John |url=http://clok.uclan.ac.uk/1155/1/archer_J_does_sexual_selection_explain_2009.pdf }}</ref> Aggression in women may have evolved to be, on average, less physically dangerous and more covert or [[Indirect aggression|indirect]].<ref>{{cite journal |doi=10.1017/s0140525x99001818 |title=Staying alive: Evolution, culture, and women's intrasexual aggression |journal=Behavioral and Brain Sciences |volume=22 |issue=2 |year=1999 |last1=Campbell |first1=Anne |s2cid=1081104 |pmid=11301523 |pages=203–14; discussion 214–52}}</ref><ref>[https://books.google.com/books?id=esDW3xTKoLIC The Handbook of Evolutionary Psychology], edited by David M. Buss, John Wiley & Sons, Inc., 2005. Chapter 21 by Anne Campbell.{{page needed|date=February 2017}}</ref> However, there are critiques for using animal behavior to explain human behavior, especially in the application of evolutionary explanations to contemporary human behavior, including differences between the genders.<ref>Zuk, M. "[https://books.google.com/books/about/Sexual_selections.html?id=-Sjsmhm82wUC Sexual Selections: What We Can and Can't Learn about Sex from Animals.]" University of California Press, 2002{{page needed|date=February 2017}}</ref>

According to the 2015 ''[[International Encyclopedia of the Social & Behavioral Sciences]]'', sex differences in aggression is one of the most robust and oldest findings in psychology.<ref name = "274956064 Gender diff">{{cite book |doi=10.1016/B978-0-08-097086-8.25100-3 |chapter=Gender Differences in Personality and Social Behavior |title=International Encyclopedia of the Social & Behavioral Sciences |pages=750–6 |year=2015 |last1=Del Giudice |first1=Marco |hdl=2318/1852940 |isbn=978-0-08-097087-5 }}</ref> Past meta-analyses in the encyclopedia found males regardless of age engaged in more physical and verbal aggression while small effect for females engaging in more indirect aggression such as rumor spreading or gossiping.<ref name= "274956064 Gender diff"/> It also found males tend to engage in more unprovoked aggression at higher frequency than females.<ref name= "274956064 Gender diff"/> This analysis also conforms with the ''Oxford Handbook of Evolutionary Psychology'' which reviewed past analysis which found men to use more verbal and physical aggression with the difference being greater in the physical type.<ref>{{cite book |doi=10.1093/oxfordhb/9780198568308.013.0025 |year=2012 |last1=Campbell |first1=Anne |chapter=Sex differences in aggression |chapter-url={{Google books|8K7Hc09xcQAC|page=365|plainurl=yes}} |pages=365–82 |editor1-first=Louise |editor1-last=Barrett |editor2-first=Robin |editor2-last=Dunbar |title=Oxford Handbook of Evolutionary Psychology |isbn=978-0-19-856830-8 }}</ref>

There are more recent findings that show that differences in male and female aggression appear at about two years of age, though the differences in aggression are more consistent in middle-aged children and adolescence. Tremblay, Japel and Pérusse (1999) asserted that physically aggressive behaviors such as kicking, biting and hitting are age-typical expressions of innate and spontaneous reactions to biological drives such as anger, hunger, and affiliation.<ref>{{cite journal |doi=10.1002/bsl.2035 |pmid=22996132 |title=Gender Differences in Physical Aggression and Associated Developmental Correlates in a Sample of Canadian Preschoolers |journal=Behavioral Sciences & the Law |volume=30 |issue=5 |pages=643–71 |year=2012 |last1=Lussier |first1=Patrick |last2=Corrado |first2=Raymond |last3=Tzoumakis |first3=Stacy }}</ref> Girls' [[relational aggression]], meaning non-physical or indirect, tends to increase after age two while physical aggression decreases. There was no significant difference in aggression between males and females before two years of age.<ref name="Landsford 2012 298–308">{{cite journal |doi=10.1002/ab.21433 |pmid=23935227 |pmc=3736589 |title=Boys' and Girls' Relational and Physical Aggression in Nine Countries |journal=Aggressive Behavior |volume=38 |issue=4 |pages=298–308 |year=2012 |last1=Lansford |first1=Jennifer E. |last2=Skinner |first2=Ann T. |last3=Sorbring |first3=Emma |last4=Giunta |first4=Laura Di |last5=Deater-Deckard |first5=Kirby |last6=Dodge |first6=Kenneth A. |last7=Malone |first7=Patrick S. |last8=Oburu |first8=Paul |last9=Pastorelli |first9=Concetta |last10=Tapanya |first10=Sombat |last11=Uribe Tirado |first11=Liliana Maria |last12=Zelli |first12=Arnaldo |last13=Al-Hassan |first13=Suha M. |last14=Peña Alampay |first14=Liane |last15=Bacchini |first15=Dario |last16=Bombi |first16=Anna Silvia |last17=Bornstein |first17=Marc H. |last18=Chang |first18=Lei }}</ref> A possible explanation for this could be that girls develop language skills more quickly than boys, and therefore have better ways of verbalizing their wants and needs. They are more likely to use communication when trying to retrieve a toy with the words "Ask nicely" or "Say please."<ref name="Hay 2011 158–75">{{cite journal |doi=10.1111/j.2044-835x.2011.02028.x |pmid=21592146 |title=The emergence of gender differences in physical aggression in the context of conflict between young peers |journal=British Journal of Developmental Psychology |volume=29 |issue=2 |pages=158–75 |year=2011 |last1=Hay |first1=Dale F. |last2=Nash |first2=Alison |last3=Caplan |first3=Marlene |last4=Swartzentruber |first4=Jan |last5=Ishikawa |first5=Fumiko |last6=Vespo |first6=Jo Ellen |s2cid=206006344 }}</ref>

According to the journal of ''Aggressive Behaviour'', an analysis across 9 countries found boys reported more in the use of physical aggression.<ref name="Landsford 2012 298–308"/> At the same time no consistent sex differences emerged within relational aggression.<ref name="Landsford 2012 298–308" /> It has been found that girls are more likely than boys to use reactive aggression and then retract, but boys are more likely to increase rather than to retract their aggression after their first reaction. Studies show girls' aggressive tactics included [[gossip]], [[Social rejection|ostracism]], breaking confidences, and criticism of a victim's clothing, appearance, or personality, whereas boys engage in aggression that involves a direct physical and/or verbal assault.<ref>{{cite journal |doi=10.1016/j.evolhumbehav.2005.11.001 |title=Sex differences in indirect aggression |journal=Evolution and Human Behavior |volume=27 |issue=3 |pages=231–45 |year=2006 |last1=Hess |first1=Nicole H. |last2=Hagen |first2=Edward H. }}</ref> This could be due to the fact that girls' frontal lobes develop earlier than boys, allowing them to self-restrain.<ref name="Hay 2011 158–75"/>

One factor that shows insignificant differences between male and female aggression is in sports. In sports, the rate of aggression in both contact and non-contact sports is relatively equal. Since the establishment of Title IX, female sports have increased in competitiveness and importance, which could contribute to the evening of aggression and the "need to win" attitude between both genders. Among sex differences found in adult sports were that females have a higher scale of indirect hostility while men have a higher scale of assault.<ref>{{cite journal |last=Keeler |first=Linda A |title=The differences in sport aggression, life aggression, and life assertion among adult male and female collision, contact, and non-contact sport athletes |journal=Journal of Sport Behavior |year=2007 |volume=30 |issue=1 |pages=57–76 |url=https://www.proquest.com/openview/19a147ae672eead5e95f7141e6116794/1 }}</ref> Another difference found is that men have up to 20 times higher levels of [[testosterone]] than women.

==== In intimate relationships ====
Some studies suggest that romantic involvement in adolescence decreases aggression in males and females, but decreases at a higher rate in females. Females will seem more desirable to their mate if they fit in with society and females that are aggressive do not usually fit well in society. They can often be viewed as antisocial. Female aggression is not considered the norm in society and going against the norm can sometimes prevent one from getting a mate.<ref>{{cite journal |doi=10.1002/ab.20404 |pmid=21748751 |pmc=4332584 |title=Developmental trajectories of aggression from late childhood through adolescence: Similarities and differences across gender |journal=Aggressive Behavior |volume=37 |issue=5 |pages=387–404 |year=2011 |last1=Xie |first1=Hongling |last2=Drabick |first2=Deborah A.G. |last3=Chen |first3=Diane }}</ref> However, studies have shown that an increasing number of women are getting arrested on [[domestic violence]] charges. In many states, women now account for a quarter to a third of all domestic violence arrests, up from less than 10 percent a decade ago.

The new statistics reflect a reality documented in research: women are perpetrators as well as victims of family violence.<ref>{{cite news|last=Young|first=Cathy|title=Feminists Play the Victim Game|url=https://www.nytimes.com/1999/11/26/opinion/feminists-play-the-victim-game.html|work=The New York Times|access-date=6 December 2012|date=26 November 1999}}</ref> However, another equally possible explanation is a case of improved diagnostics: it has become more acceptable for men to report female domestic violence to the authorities while at the same time actual female domestic violence has not increased at all.<ref>{{Cite web|title=What To Do If Your Partner Has A Steamroller Personality|url=https://newvisionpsychology.com.au/couples-counselling-sydney/partner-has-steamroller-personality/|url-status=live|access-date=|website=|language=|archive-url=https://web.archive.org/web/20210907064134/https://newvisionpsychology.com.au/couples-counselling-sydney/partner-has-steamroller-personality/ |archive-date=7 September 2021 }}</ref> This could be the case in a situation where men had become less ashamed of reporting [[Domestic violence against men|female violence against them]]⁠{{nowrap|{{px2}}{{mdash}}{{px2}}}}such a situation could conceivably lead to an increasing number of women being arrested despite the actual number of violent women remaining the same.

In addition, males in competitive sports are often advised by their coaches not to be in intimate relationships based on the premises that they become more docile and less aggressive during an athletic event. The circumstances in which males and females experience aggression are also different. A study showed that social anxiety and stress was positively correlated with aggression in males, meaning as stress and social anxiety increases so does aggression. Furthermore, a male with higher social skills has a lower rate of aggressive behavior than a male with lower social skills. In females, higher rates of aggression were only correlated with higher rates of stress. Other than biological factors that contribute to aggression there are physical factors as well.<ref>{{cite journal |last1=Al-Ali |first1=Majed. M. |last2=Singh |first2=Ajai Pratap |last3=Smekal |first3=Vladimir |title=Social anxiety in relation to social skills, aggression, and stress among male and female commercial institute students |journal=Education |year=2011 |volume=132 |issue=2 |pages=351–61 |url=https://www.questia.com/library/journal/1G1-278759334/social-anxiety-in-relation-to-social-skills-aggression }}</ref>

==== Physiological factors ====
Regarding sexual dimorphism, humans fall into an intermediate group with moderate sex differences in body size but relatively large [[testes]]. This is a typical pattern of primates where several males and females live together in a group and the male faces an intermediate number of challenges from other males compared to exclusive [[polygyny]] and [[monogamy]] but frequent [[sperm competition]].<ref name=Oxford2007>{{cite book |doi=10.1093/oxfordhb/9780198568308.013.0030 |year=2012 |last1=Low |first1=Bobbi S. |chapter=Ecological and socio-cultural impacts on mating and marriage systems |chapter-url={{Google books|8K7Hc09xcQAC|page=449|plainurl=yes}} |pages=449–62 |editor1-first=Louise |editor1-last=Barrett |editor2-first=Robin |editor2-last=Dunbar |title=Oxford Handbook of Evolutionary Psychology |isbn=978-0-19-856830-8 }}</ref>

[[Evolutionary psychology]] and [[sociobiology]] have also discussed and produced theories for some specific forms of male aggression such as [[sociobiological theories of rape]] and theories regarding the [[Cinderella effect]]. Another evolutionary theory explaining gender differences in aggression is the [[Male Warrior hypothesis]], which explains that males have psychologically evolved for intergroup aggression in order to gain access to mates, resources, territory and status.<ref name=":1" /><ref name=":2" />