Week 8 Competition, Aggression & Violence Evolutionary Psychology

Week 8

Competition,

Aggression

&

Violence

Evolutionary Psychology

Evolutionary Psychology

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.

Evolutionary PsychologyWeek 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.

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).


Sex of Offender

Male Female Both

Sex of Victim

Male 205830 68% 31545 10% 237375 78%

Female 60838 20% 4831 2% 65669 22%

Both 266668 88% 36376 12% 303044

Uniform Crime Reports [United States]: Supplementary Homicide Reports, 1976–1999

What types of homicide are most common?


• 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?


• 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?




• 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 are young men particularly at risk?



• When competition for resources is perceived as most acute;

Relative deprivation

• When resources are being defended;

Male sexual proprietariness.

Questions




When are they most likely to resort to violence?


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 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.


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.


Future discountingThe 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 & DalyBMJ 1997;

314:1271


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.


Documents

Week 8 Competition, Aggression & Violence Evolutionary Psychology