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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
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GenderReductionistEthical Guidelines?Nature vs. NurtureAnimal StudiesDeterminsm vs. Free WillEthnocentricism
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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
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GenderReductionistEthical Guidelines?Nature vs. NurtureAnimal StudiesDeterminsm vs. Free WillEthnocentricism
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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)
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AO3
GenderReductionistEthical Guidelines?Nature vs. NurtureAnimal StudiesDeterminsm vs. Free WillEthnocentricism
44