Evolutionary Explanation of aggression

Outline & Evaluate Hormonal Explanations of Aggression (20 marks)A01:Chemicals that regulate & control bodily functionsTestosterone = Androgen (male hormone, released from testes)10x higher in males than females (adrenal gland)15-25yrs = peak testosterone age and age most likely to commit violent crimes Animal studies can show effects of removal of testosterone sources (neutering) Possible links between Low Levels of Cortisol + aggression

A02Higher in athletes from aggressive sportsHigher in more aggressive prison populations (Dabbs, 1995)Can increase aggression in castrated mice (Wagner)Can increase anti-social competition in men (Harrison)Possible link with low cortisolHOWEVER Data generated from small, specific (prison) samplesGeneral population shows 0.14 correlation (other factors)Alternative explanation may be that testosterone increases social dominancenot aggression

AO3

GenderReductionistEthical Guidelines?Nature vs. NurtureAnimal StudiesDeterminsm vs. Free WillEthnocentricism

3

Evolutionary Explanation of aggressionUnderstanding of Evolutionary PsychologyEvolutionary theory Applied to AggressionKey words: Parental Investment, Cuckoldry, Sexual Jealousy, Adaptive

CuckoldrySexual JealousyAdaptiveParental InvestmentInclusive Fitness

Inclusive FitnessMeasure of how successful individuals are in passing on a high proportion of their genes to succeeding generations

What is evolutionary Psychology?EP seeks to identify which human psychological traits are evolved adaptations that is, the functional products of natural selection or sexual selection in human evolution

Evolutionary psychology

Evolutionary PsychologyAll behaviour is rooted in ensuring reproductive success

Phobias, anorexia, gym, make up, dancing 10

Evolutionary PsychologySLT = we can learn to be aggressiveDeindividuation = situations make us aggressiveInstitutional = Institutions make you aggressiveGenetic/Neural/Hormonal = Our biology make us predisposed to aggressionEvolutionary = The Ultimate Reason for Aggression

Defend food / mates11

Evolutionary AggressionWhy was it adaptive to behave aggressively?

How might aggressive behaviour in modern day be associated with reproductive success?

Evolutionary PsychologyLorenz (1966)

Functions of Aggression1. Ensure only the fittest & strongest mates selected for reproduction2. Ensure survival of offspring3. Distribute a species in a balanced way in territories

Parental InvestmentAny investment by the parent in an individual offspring that increases the chance of offspring survival

Involves provision of resources, (food, energy, time, territory)

Parental InvestmentThere is asymmetry in parental investment in humans

Female egg cell is much more costly to produce than male sperm cellFemales must nourish the offspring for 9 months, she is therefore limited by number of offspringIn Western cultures, females breast feed for between 3-12 months

Females must be choosier when it comes to potential male mates

Females compete for quality of male matesMales compete for quantity of female mates

69!2000!

Geghis 2000 gravata - 6916

Evolutionary PsychologySexual Jealousy based on suspected or imminent sexual infidelity

Evolutionary psychologySexual Jealousy can be used as a mitigating factor in court

In many cultures, a man has the right to beat or even kill his unfaithful wife

In Western societies, murder charges can be reduced to manslaughter if the male killed another male who was sexually involved with the killers wife this is not the same for women.

cuckoldryInvesting in offspring that are not their own

Females can be certain if a child is their own, males cannot

Therefore males have a greater concern about the fidelity of their mates than females

Cuckoldry risksRetaliation from male

Abandonment (loss of resources)Loss of invested resources

Loss of reproductive success

A01 evolutionary explanationCuckolded men risk losing resources and reproductive opportunity. Males evolved aggressive mate-guarding strategies to prevent being cuckolded. These are driven by sexual jealousy, an adaptation evolved in males to deal with parental uncertainty. Sexual jealousy prevents the female mating with others so it is an adaptive response.

CuckoldrySexual jealousy may have evolved as a solution to these problems

Buss (1992) Which is worse?A) The knowledge that your partner has had sex with someone elseB) The knowledge that your partner has developed a deep emotional bond with someone else

Buss (1992)85% of women chose option B deep emotional bond

60% of men chose option A

(The majority of the 40% of males who had chosen option A had never been in a committed sexual relationship)

Which route to take1. Sow your wild oats with lots of women, hoping that at least some of them mother your children

Or 2. Stick to 1 woman and watch her like a hawk so you can be sure shes mothering only your children

Shackleford (2005) Claimed that men have evolved mate-retention strategies to deter their mate from leaving/cheating.

He found that the more of these strategies seen in a relationship, the more likely female-directed abuse will occur.

Shackleford (2005) 1. Vigilance

2. Emotional Manipulation

3. Monopolisation of Time

4. Possessive Ornamentation

Look in books for examples of each26

Shackleford (2005)72% of women who reported partners using direct-guarding (not allowing them to talk to other men) required medical attention after an assault by their partner

Aggression is an adaptive response to ensure reproductive success

Daly & Wilson (1988)Peak reproductive age in males is early 20s

This age is also the most likely age to commit same-sex homicide.

Daly & Wilson (1988)

Same-sex murder rates reflect evolved aggression due to sexual jealousy

Daly & Wilson (1988)A lack of resources increases male-male competition and risk of murder

Daly & Wilson (1988)Threat to male status

Females attracted to men with higher statusTherefore men seek statusLoss of male status = loss of potential mates + possibly resources.

What we know so farFactors affecting reproductive success can increase aggressionA02(Buss Males sex>emotional bond)Shackleford More mate-guarding = more violenceDaly & Wilson peak reproductive males = peak violence - More male-male murders than female - Less resources = more male-male murders

AO3

GenderReductionistEthical Guidelines?Nature vs. NurtureAnimal StudiesDeterminsm vs. Free WillEthnocentricism

33

Female AggressionStudies have found that females will use more Verbal Aggression than males

How can this be explained by Evolutionary Psychology?

Size of females evolved34

Maladaptive Aggression?Ghiglieri (1999)Male lions & cheetahs have been observed killing offspring (usually of rival males)

Reduces Inclusive Fitness (reproductive success) in rivalsMore resources and less competition for own offspringCauses Rivals lioness to go into oestrus (heat) sooner, allowing killer to impregnate them with own offspring.

Other types of Aggression?

Other types of AggressionLorenz (1966)

Functions of Aggression1. Ensure only the fittest & strongest mates selected for reproduction2. Ensure survival of offspring3. Distribute a species in a balanced way in territories

Lorenz - Xenophobia & Genocide Violence towards other cultures is common

Lorenz believes this is due to Territorial Aggression driven by evolved, primal survival tactics.

Xenophobia & GenocideWaller (2002)

Humans have evolved living in groups which need defined boundaries creating in-groups and out-groupsAllows for resources to be shared equally, reduces potential of free-ridersReduces reproductive competition We have evolved xenophobic attitudes towards out-group members to protect our ownGenocide is the consequence of this xenophobia

However Individual Differences (not all men act aggressively towards unfaithful partners)Suggests that violence is not a universal response to sexual jealousy, thus not completely evolutionary

Cultural Differences in Aggressive Behaviour

Cultural Differences in Aggressive Behaviour (Buss & Shackleford, 1997)

Yanomami of South AmericaMale violence is required to attain status

Kung San of NamibiaAggression leads to irreparable damage of the aggressor

Describe & Evaluate the Evolutionary Explanation of Aggression. (8 + 16 marks)A01

Lorenz 3 functions of aggressionAdaptive Increase reproductive success & thus inclusive fitnessKey words Sexual Jealousy CuckoldryMate-Retention StrategiesMale-male competitionTerritorial Aggression

Try and write a paragraph now including all key words42

Describe & Evaluate the Evolutionary Explanation of Aggression. (8 + 16 marks)A02:

Shackleford More mate-retention strategies = more violence(supports notion of sexual jealousy driving aggression)Daly & Wilson Age / Male-male homicide / Resources / Status(supports idea of reproductive competition driving aggression)Female Aggression = verbal (females less physical, verbal aggression reduces status and deters males)Other types of Aggression Xenophobia (Waller, 2002)(supports idea that aggression is created by drive for in-group to survive)

43

AO3

GenderReductionistEthical Guidelines?Nature vs. NurtureAnimal StudiesDeterminsm vs. Free WillEthnocentricism

44