1. Week 8 Competition, Aggression & Violence Evolutionary Psychology

2. Running Order Development & aggression Who kills whom? Male-on-male Male-on-female Mate guarding & jealousy Female-on-male Female-on-female Social & environmental factors.

3. Evolutionary Psychology Week 8 - Competition, Aggression & Violence Aim To analyse the conditions that promote acts of interpersonal competition, with special reference to homicide. Reward By the end of this session you should be better able to predict who is most likely to be violent to whom and when.

4. Why study homicide? Relatively unbiased measure of interpersonal conflict. Less bias in police files than for assaults. Issues over which people are willing to kill are presumably those that they care most about. What do we care about most? Resources (e.g. land, property, money). Status (e.g. reputation). Kin (e.g. protection of kin). Reproduction (e.g. fidelity of partner). Evolutionary Psychology Week 8 - Competition, Aggression & Violence

5. Sex of Offender MaleFemaleBoth Sex of Victim Male20583068%3154510%23737578% Female6083820%48312%6566922% Both26666888%3637612%303044 Uniform Crime Reports [United States]: Supplementary Homicide Reports, 1976–1999 What types of homicide are most common? Evolutionary Psychology Week 8 - Competition, Aggression & Violence

6. The human male psyche has evolved to be more risk accepting in competitive situations than the female psyche. Consequence of effective polygyny: Fitness: male variance > female variance. Greater fitness variance selects for greater risk acceptance in pursuit of scarce means to the end of fitness. Questions Why a sex difference? Why are men violent? Why are young men particularly at risk? When are they most likely to resort to violence? Evolutionary Psychology Week 8 - Competition, Aggression & Violence

7. Intra-sexual competition. Lethal violence between unrelated men occurs when they compete. Resources, sexual opportunities, social status - all means to the end (fitness). Rate of male-male homicide should be sensitive to local intensity of intra-sexual competition. Questions Why a sex difference? Why are men violent? Why are young men particularly at risk? When are they most likely to resort to violence? Evolutionary Psychology Week 8 - Competition, Aggression & Violence

8. Direct competition for limited resources. Pecking order effects. Honour, trivial altercations & status anxiety; –Far from trivial for men concerned. –Reputation and social status at stake. –Determinants of fitness in ancestral environments. Questions Why a sex difference? Why are men violent? Why are young men particularly at risk? When are they most likely to resort to violence? Evolutionary Psychology Week 8 - Competition, Aggression & Violence

9. When competition for resources is perceived as most acute; Relative deprivation When resources are being defended; Male sexual proprietariness. Questions Why a sex difference? Why are men violent? Why are young men particularly at risk? When are they most likely to resort to violence? Evolutionary Psychology Week 8 - Competition, Aggression & Violence

10. Male-on-female aggression Intimate relationship Emotional attachment Reproductive alliance Shared fitness interests Axiomatically, it cannot be adaptive to kill the means by which one would enjoy reproductive success. Motives for uxoricide Accusation of infidelity His non-acceptance of her decision to terminate the relationship Conflict over his more general efforts to control her Male sexual proprietariness & jealousy. Evolutionary Psychology Week 8 - Competition, Aggression & Violence

11. Evolutionary logic of male sexual proprietariness Asymmetric costs of sexual reproduction Maternity certainty vs paternity uncertainty Male sexual jealousy evolved as an anti-cuckoldry mechanism Violent responses to cues of sexual infidelity may have been adaptive in ancestral environments – and in some current environments Homicide, taken as an extreme manifestation of violence and coercion, is not necessarily an adaptive strategy. Evolutionary Psychology Week 8 - Competition, Aggression & Violence

12. Female-on-female Paucity of a pay-off in terms of reproductive success Female mate value is not so sensitive to status. Impact on mate value of physical damage is greater for females - appearance & gestation. Indirect aggression Social intelligence has evolved in response to the need to compete whilst minimising the risk of physical damage. Indirect aggression is a more sophisticated form of aggression than direct aggression. Females are as aggressive as males but also more sophisticated in their tactics - theory of mind. Evolutionary Psychology Week 8 - Competition, Aggression & Violence

13. Future discounting The idea is that people who engage in risky criminal activity tend to discount the future more steeply. Impulsivity Short time horizons Impatience Myopia Lack of self control Incapacity to delay gratification But is FD irrational? Steep discounting may be a ‘rational’ response to information that indicates an uncertain or low probability of surviving to reap delayed benefits, for example, and ‘reckless’ risk taking can be optimal when the expected profits from safer courses of action are negligible. Wilson & Daly BMJ 1997; 314:1271 Evolutionary Psychology Week 8 - Competition, Aggression & Violence

14. Social and environmental factors Inequity in the distribution of material resources predicts homicide rates. Why? Increasing socioeconomic inequality increases the intensity of male-male competition for resources - resources that would have had fitness benefits for males in ancestral environments. Only a few males become prized by females which increases competition between them. Evolutionary Psychology Week 8 - Competition, Aggression & Violence