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Chapter 10

CHAPTER 10 NOTES - Evolutionary Psych

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PSYC 3420
Irwin Silverman

CHAPTER 10: AGGRESSION AND WARFARE INTRODUCTION: • of the more than 10 million animal species that exists, including 4 thousand mammals, only two species have been documented to show male-initiated coordinated coalitions that raid neighbouring territories and result in lethal attacks on members of their own species: chimpanzees and humans • humans and chimpanzees form aggressive male-bonded coalitions in which members support each other in a mutual quest to aggress against others • in all cultures, men commonly have bonded together to attack other groups or to defend their own AGRESSION AS A SOLUTION TO ADAPTIVE PROBLEMS • below are leading candidates for adaptive problems for which aggression might be an evolved solution Co-opt the Resources of Others • humans more than any other species stockpile resources that have been valuable for survival and reproduction • for example: land, food, water, tools • aggression is also a means of co-opting the resources of others • gaining access to these resources are done by social exchange, stealing, or trickery • at the individual level, one can use physical force to take resources from others • e.g. Bullies who take lunch money or books • childhood aggression is commonly about resources such as toys and territory • adult forms including beating and muggings to get money or other goods • the threat of aggression might be enough to secure resources from others • men often form coalitions to forcibly co-opt the resources of others • among the Yanomamo, male coalitions raid tribes and take food and reproductive aged women • warfare has been used to co-opt the land possessed by others Defend Against Attack • victims of aggression might lose in the currency of status and reputation • the loss of face or honour entailed in being abused can lead to further abuse by others • aggression therefore can be used to defend against attack • many defend against attack to prevent harm to one's mate or children Inflict costs on Intrasexual Rivals • same sex rivals going for the same resources such as valuable members of the opposite sex EVOLUTION CHAPTER 10 page 1 • aggression to inflict costs of rivals an range from verbal bars to beating and killings • men and women both derogate their same-sex rivals impugning their status and reputation to make them seem less desirable • men sometimes kill other men they find out have had sex with their wives or girlfriends • because evolution operates according to differences in designs, a cost inflicted on a rival can translate into a benefit for the perpetrator Negotiate Status and Power Hierarchies • Aggression functions to increase one's status or power within existing social hierarchies • e.g. Among the Yanomamo men who had survived many club fights are admired and feared and had gained status and power e.g. Modern societies in the form of boxing matches • men who expose themselves to danger in warfare to kill enemies are regarded as brave and experience an elevation in their status • aggression within many groups can result in a status decrement e.g. A prof who punches another prof in the face at a meeting • the key to the status elevation hypothesis is to specify the evolved psychological mechanisms that are sensitive to the social contexts in which aggression pays Deter Rivals from Future Aggression • getting the reputation that you are aggressive might function to deter aggression and other forms of cost infliction from others • aggression and the reputation for aggression an act as deterrents • e.g. You would think twice about flirting with the girlfriend of a member of the Hells Angels Deter Long-Term Mates from Sexual Infidelity • aggression and the threat of aggression function to deter long-term mates from cheating • male sexual jealousy is the leading cause of spousal battering/beating • some men do beat their wives or girlfriends to deter them from consorting with other men The Context-Specificity of Aggression • aggression is not a unitary, monolithic, or context-blind strategy • aggression is likely to be highly context specific, triggered only in contexts that resemble those in which our ancestors confronted certain adaptive problems and reaped benefits • men who have lower mate value than their wives e.g. Loss of a job are more likely to beat their wives in order for the women not to leave or cheat • aggression by definition inflicts costs on others, and those others cannot be expected to absorb the costs passively or with indifference, which can cause EVOLUTION CHAPTER 10 page 2 escalating cycles of aggression as in the family feud between the Hatfields and the McCoys • cultures differ in whether aggression enhances or diminishes status, among cultures of honer, failure to aggress when insulted can lead to status loss • e.g. The failure to kill a daughter who engaged in premarital sex might result in a lowering of status of the rest of the family • another dimension of cost is the ability and the willingness of the victim to retaliate • bullies select victims who cannot/will not retaliate • e.g. The husband of a women with 4 brothers and a powerful father will think twice before beating her • the presence of extended kin is therefore one context of cost that should moderate spousal violence • findings of variability of aggression across contexts, cultures, and individuals in no way falsify particular evolutionary hypotheses • aggression is evoked by particular adaptive problems confronted in particular cost-benefit contexts WHY ARE MEN MORE VIOLENTLYAGGRESSIVE THAN WOMEN? • In all cultures, men are more often the killers and the majority of their victims of other men • an evolutionary model of intrasexual competition provides the foundation for such an explanation • it starts with the theory of parental investment and sexual selection • males can produce more offspring than females can because of the difference in minimum obligatory parental investment • this difference leads to differences in the variances in reproduction between the sexes • the greater the variances in reproduction, the more election favours riskier strategies (including intrasexual competition) within the sex that shows the higher variance • elephant example: the more intense the effective polygyny, the more dimorphic the sexes are in size and form • elephant seals are highly sexually dimorphic in weight, with males weighing 4 times what the females weigh • chimpanzee males weight 2x than females • humans weigh roughly 18% heavier than females • within primate species, the greater the effective polygyny, the more pronounced the sexual dimorphism, and the greater the reproductive variance between the sexes • effective polygyny means that some males gain more than their “fair share” of copulations while other males are shut out entirely, banished from contributing to the ancestry of future generations • polygyny selects for risky strategies, including those that lead to violent combat with rivals and those that lead to increased risk taking to acquire the resources needed to attract members of the high-investing sex EVOLUTION CHAPTER 10 page 3 • violence can occur at the top and the bottom of the hierarchy- homicide data reveal that men who are poor and unmarried are more likely to kill • there are two sides to the use of aggression: 1) aggression by a male to “win big” and gain access to multiple mates 2) aggression to avoid total reproductive failure • selection filters out those who fail to take risks • males are more often the perpetrators of violence because they are the products of a long history of mild but sustained effective polygyny characterized by risky strategies of intrasexual competition for access to females • men are the victims of aggression far more than women are because men are in competition primarily with other men • the forms of aggression committed by a women are typically less violence and less risky than men- facts that are accounted for by the theory of parental investment and sexual selection • selection may operate against women who take the large physical risks entailed by aggression • women need to place a higher value on their own lives because infants depend on maternal care more than paternal are • women's evolved psychology should reflect greater fearfulness of situations that pose a physical threat of bodily injury BOX 10.1: The Recalibration Theory of Anger • one source of conflict emerges when you believe that another person does not value your welfare as much as you believe that person should • a romantic partner might not meet your sexual or emotional needs at the level to which you believe you are entitled • the recalibration theory proposes that feeling and expressing anger functions to increase (recalibrate) the value that the target of your anger places on your welfare • the recalibration theory predicts that physically formidable men and physically attractive women should be more prone to anger, have greater success in resolving soil conflicts in their favour, and experience a greater sense of entitlement than less formidable men and less attractive women • in a study, stronger men (not women) reported more proneness to anger, a more frequent history of fighting, more success in prior social conflicts, a greater perceived utility of using aggression and a greater sense of entitlement • the emotion of anger, a key emotion that motivations aggression, has a coherent adaptive logic Evidence for Sex Differences in Same-Sex Aggression • A Meta-Analysis of Sexy Differences in Aggression • effect size is the magnitude of the sex differences • .80 is large .50 is medium and .20 is small EVOLUTION CHAPTER 10 page 4 • aggressive fantasies .84, physical aggression .60, imitative aggression .49, and willingness to shock others in a study .39 • all show greater male scores on aggression • no evidence for a sex difference in scores on the hostility scale (.02) • men use aggression more than women in a variety of forms, and the effect sizes tend to range from medium to large • Same-Sex Homicides • in every culture for which there were data, the rate at which men kill other men far exceeds the rate at which women kill other women • there is no evidence that the women in any society have ever approached the level of violent conflict prevailing among men in the same society • Same-Sex Bullying in Schools • in a study, 54% of middle school boys reported engaging in bullying an girls were 34% • 36% of the boys but only 9% of the girls reported being physically hurt • 10% of boys but only 6% of girls reported having had their belongings taken away from them • on two measures of bullying however, girls scored higher: 74% of girls reported that others had called them nasty named but only 57% of boys reported this • the most frequently used names spread by girls about other girls involved terms such as bitch, slut, and whore • these kinds of bullying were common among high school girls but absent among the middle school students, suggesting a rise in intrasexual mate competition • in another study, boys showed more than 3 times the rates of direct physically aggression • indirect aggression e.g. Gossiping the 15year old boys showed 25% higher rates than the same-age boys • males engage in forms of aggression more frequently than females but when females aggress, they tend to use less violent methods such as verbal derogation of their competitors • Aggression in an Australian Aboriginal Community • anthropologist spent several months in a community to study it • Burbank coded the 793 aggressive episodes into categories and examined sex differences • men overwhelmingly resorted to more dangerous aggression than women did • men accounted for 97% of the aggressive episodes in which a dangerous weapon was used • The Young Male Syndrome • young men appear to be the most prone to engage in risky forms of aggression EVOLUTION CHAPTER 10 page 5 • through age ten, male sand females do not differ in the likelihood of becoming homicide victims • at adolescence, killings of males start to skyrocket, reaching a peak in the mid- twenties • at that age, men are 6 times more likely than women to become the victims of homicide • after men's mid-twenties, their victimization begins to drop sharply, because they begin to avoid physically risky tactics • why would men engage in these behaviours at the peak of physical prowess • over the course of human evolutionary history, a young man seeking a wife had to display formidable physical prowess in hunting, tribal raids, tribal defense, and the ability to defend his interests • what makes humans unique is the importance of cultivating a reputation which could affect a man's lifetime survival and reproductive success • the finding that displays of violence by young men are almost invariably performed in the presence of an audience suggests that risky displays are also designed to impress peers and form a good social reputation • across a variety of states and countries, they discovered that the higher the percentage of males in the age group of 15 to 29, relative to the percentage of males 30 years or older, the higher the levels of aggression • this link s so strong that the proportion of young males in a population might be the best predictor of violent aggression • in sum, the evolutionary explanation of the “young male syndrome” can account for: variations in collective aggression, the sudden surge in muscle strength in males from puberty through the mid-twenties, the surge in aerobic capacity in adolescence and the mid-twenties, and especially the surge in measures of quick energetic bursts that might be needed for risky forms of aggression CONTEXTS TRIGERING MEN'S AGGRESSION AGAINST MEN • Marital and Employment Status • killers and victims often share similar characteristics such as being unemployed and unmarried • lacking resources and being unable to attract a long-term mate appear to be social contexts linked with male-male homicides • Status and Reputation • one of the key motives of male-male homicide is the defense of status, reputation and honour • “trivial altercations” • typical case is the barroom verbal altercation that escalates out of control as no one wants to be the one that backs down because of fearing humiliation in the eyes of their peers • the link between status and aggression has also been documented in laboratory experiments • participants were first primed with status cues EVOLUTION CHAPTER 10 page 6 • men, but not women, reacted with greater direct aggression after their motive for status was activated • humans evolved in small-group living in which status and reputation were vital to a man;s access to resources and mating opportunities • our final indicator of the links
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