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Define Agression

any form of behaviour directed toward the goal of harming or injuring another living being who is motivated to avoid such treatment” (Baron & Richardson, 1994, p, 7)


what are types of aggression?

verbal vs physical

• Direct (where aggressor is clearly identifiable to the victim) versus indirect (aggressor not visible)
• Instrumental (targeted towards a goal) vs. expressive (internal emotional state)


what is the equation for why aggression may occur

potential(aggression) = (p. rewards – p. costs)


how can the equation for aggression be used to explain sex differences?

o Males’ rewards vs females costs (males generally get rewards whilst females get costs)


males tend to be more aggressive, but what are some similarities? And what can we infer from this?

• High Correlation between sexes over
o Regions and nations
o Age (fairly well) is v hard to see across age as homicide is so much lower than men but spike in early 20s for both.
• Similar developmental predictors (Gotfredson & Hirschi, 1990)
o Social Class/ SES
o Insecure attachment
o Parental discord/ conflict and separation
o Poor school achievement
• So underlying psychology in terms of what is driving men and women to aggressive behaviour seems to be fairly similar.


what are differences in M and F aggression?

1)men are more aggressive
2) this magnitude increases with the severity of the aggression.


study showing gender differences in male and female aggression

• Archer 2009- meta analysis- sex differences in types of aggression for different methods of assessment.
o Experimental (sudo- create a trigger and see response)- medium effect physical agg small for verbal
o Self reports- large physical small verbal
o Group observations- medium/ large physical very small verbal
o Peer reports- large physical medium verbal
o Teacher reports- small to medium both
o Combined- get very large for physical and medium for verbal
• So see a fairly consistent picture for male aggression bias particularly for physical aggression.


evidence that magnitude of gender difference increases with gender

• Archer (2014)
• Indirect= no sex difference, verbal= small, physical= medium, criminal assault/ weapons= large, homicide= very large
• Putting this into context… typical physiological sex differences fall in range with verbal (small meaningful). When it comes to sex difference between criminal assault/ weapons it is about same as gender difference between emotion decoding and for homicide is about the same as height so is blindingly obvious.


stats that support men being more violent

-89% of violent rime is committed by men (US Bureau of Justice Statistics, Federal sentencing records: 1996, 1997, 1998, 1999…)

->90% of same-sex homicides are male-male (Daly & Wilson, 1998, homicide) female female homicide is rare


but what can we say about thresholds and M and F aggression?

Differences in rates of aggression combined with similarities in predictors of aggression suggest a threshold difference rather than two sex-specific aggression systems. It is not that they are separate things but males and females have different thresholds of when levels of aggression are elicited.


what explanation for male aggression focuses on Bateman's principle?

what supports this?

Daly and Wilson (1988)- they really focused in on Bateman’s principle of fitness variance and mate competition.
• Rank leads to reproductive success
• =high risk/ high gain
• Thus, if you can use physical aggression to gain rank then yes it is high risk (death) but the benefit of dominating matings is really high.

disproportionate effect of winners Dogon data Brown et al. men at top not many of them getting high rates of reproductive success but because they are they are disproportionately represented in the gene pool in the following generation. So you don’t need a lot of males for their genotypes to be disproportionately represented in the gene pool.


research supporting idea of aggression and rank in primates

Cowlishaw & Dunbar (1991) review where they looked across species if you include sub adults (juveniles) then association between rank and reproductive success was always positive. If you exclude juveniles (because they are not fully active in terms of mating yet), then you do get some inverse results for high rank males within their own group, but still greater tendency in primates for high rank males to be achieving greater reproductive success.


research supporting idea of aggression and rank in humans

Perusse (1986)- found that males who are higher ranked within companies tend to have (not greater reproductive success) but greater potential reproductive success ie. they slept with more women but contraception was getting in the way of reproduction. Not a fantastic study
Josephson’s Mormons- clear evidence that achieving rank in hierarchical structures scenario is associated with greater reproductive success.
BM’s Kipsigis- males who acquire more wealth in terms of herds have more wives and offspring.
• Adaptive aggression- securing scarce resources
• Routes to status via Resource holding potential (PHP); Key point however is that there are multiple routes to success. Modern humans have jobs, money (evolutionary novel). Outside of west potentially we have hunting prowess, but we see a lot of male-male competition with wealth and jobs.
• Routes to status where RPH is low?


what may socio-economic effects have to do with aggression and support for this.

In every data set you look at aggression is highest in late teens/ early twenties ie. aggression is greatest when men tend not to have high status jobs, males feel in competition with one another, a lack of resources and want to mate thus aggression may come out more than when older and have more resources on your side.

• Controlling for age, same-sex violence/ violent crime are more frequent among:
o Non-married men and then unemployed (Daly and Wilson, 1988)
o When unemployment is high homicide is high- suggesting that financial pressures are effecting male-male violent behaviour.
o Butchart & Engstrom (2002)- essentially looked at inequality- GDP (how wealthy), GINI (how distributed is the money) in teens and early twenties. Can explain up to 70% of homicide rates by looking at how wealthy a country is and its inequality. High rates of inequality (the harder it is for some to acquire wealth) the higher the rates of aggression.


what can reduce aggression?

• Becoming a father/ being partnered is also associated with a reduction in being criminally violent. Controlling for age, same-sex violence/ violent crime are more frequent among non-married men and the unemployed and non-fathers than fathers (Boothroyd & Cross, 2016). Only focused on forms of theft- robbery (where you have to physically confront someone) to larceny (no confrontation). Of convicted thefts a much lower proportion are violent for the women than men and within men and women parents are much less likely 90-60% in men for violent theft. Partnered men show sig lower rates than being violently criminal whether they are a father or not but having kids reduces it more.


how has it been argued that paternity has a role in reducing violence?

• Has been argued that all of this can be explained by thinking about much broader vertebrate patterns in T as a regulator of male-male competitive behaviour which is targeted to achieve matings.


Outline Challenge hypothesis

• Wingfield et al. (1990) Challenge hypothesis essentially argued that if T is regulating male-male competitive behaviour and is centred around mating behaviour then what we should see is that patterns of T within a species should follow whatever the reproductive system of that species is. E.G. spikes in T as pair is forming but if there is no remating then T should drop and stay lower through repeat mating season. If there are less males to compete with you wont see much T duing early mate search phase. If re-nesting (break up pair bond for another) then should see another spike in T at this point. If species where lots of male challenge see spikes in Testosterone spikes consistently. Basically argued that Patterns of T should be predictable based on the mating environment of a species.


support for challenge hypothesis in non-humans?

o Muller & Wrangham (2004) using chimps they compared female oestrus (maximal swelling) increase in charging displays in males sig increase in chses and attacks between males, during these days of maximal swelling T levels in group were sig higher (really obvious female fertility). When females were most fertile ie. when most worth fighting with other males most worth fighting other males.

o Ricon et al. (2017) Barbary macaques- unlike chimps who have a cycle they have a mating season where all females come into oestrus at the same time. T starts to increase just before the mating season starts and then decreases post mating season. A few weeks before mating season ranks become unstable. Aggression rates higher in mating season and whilst mating dyads are forming. T here is very temporally aligned with when males are competing with each other to form mating pairs.


who reviewed challenge hypothesis and what were their hypotheses?

o Archer (2006) Review in humans:
 Six hypotheses to understand if challenge hypothesis was useful for understanding aggression in humans. This is what challenge hypothesis would predict

 H1- There is no increase in aggression at puberty
 H2a- Men respond to sexual arousal with increased T-
 H2b- Men respond to competition with increased T- yes
 H3- The T response to challenge increases with aggression
 H4- T levels are lower among paternal men
 H5- Aggressive dominance is correlated with T levels – same as H3
 H6- T is associated with alternative life history strategies.


what can be said in generally about men responding to sexual arousal with increased T?

hard to measure but some evidence to support this


exploring competition winners and losers- what found?

Zilioli & Watson (2014)
Showed that T levels remained stable across competition in winders but decrease significantly for competition losers.


support for the notion that women do have things to fight about in humans

Borgerhoff Mulder talk 21st Nov 2017- studied Pimbwe women where pair bonds are v unstable and men are coming and going women’s reproductive success increases with a greater number of sexual partners. (other way round than normal). Women RS is following a pattern would expect of men- so clearly women do have reason to compete


support for the notion that aggression for women does have benefits

Pusey et al (1997)- data in chimpanzees finding that the higher ranked females have more surviving offspring than lower rank female. Preferential resources but also because higher rank females can stress and harass the lower rank females and their offspring and occasionally kill the offspring- clear benefit in offspring survival.


evidence to support the notion that when in competition females fight more in animals

Cheney et al 2012- Chacma baboons- very clear competition for the alpha males (infants sired by alpha males more likely to have own reproductive success). As the male to female sex ratio becomes more biased there is an increase in female specific aggression. Also as number of females increases the female mortality rate also increases presumably as a result of aggression. And if looking at social bonds between the females, high score= same groups formed and remain low= chopping and changing between affiliations- in chacma baboons the more females there are relative to males, the less stable the affiliations are again suggesting competition for males and resources is having an effect on females and their social bonds


what can we say overall about violence in non-human primates?

Overall clearly we have comparative evidence that Female-female competition almost certainly exists in non-human primates and that there is reason for it to exist and it can influence the mortality of them and their offspring


who devised 'a few good men' theory and outline

Ann Campbell did a lot of work in the early 80s where she looked at girl gangs in new York and one of the themes that emerged is that there is a relatively limited number of good men. High rates of male unemployment and incarceration and thus female competition for pair bonds is large.
A focus on males with money, not in prison and treating girls well- whatever happens with relationship at least you’re treated well in it.
• ‘It’s hard to get a good man and girls grab any fella that treat you special…It’s just tight out here ‘cause we ain’t got nothing but girls, girls, girls an the guys got their pick. We just start fighting each other over the same giys” (Taylor, 1993)
More direct competition- fighting over reputation and competition over men not resources.


If women do have things to fight about then why is it theorized that this is so much less common in females?

Campbell (1999)- argument was that it is to do with the need for maternal care of offpring- the single most important thing a woman can do in terms of raising offspring is to stay alive. Sear and Coall found a positive effect between mother being alive and child staying alive. There is no evidence that finds that a mother who dies doesn’t negatively effect child survival. Fathers are about 50/50 whether they are important or not dependant on environmental niche they are in.

see data on impact of mother's death on infants


data on impact of mother's death on infants

Pavard et al. 2005

• Quebec records 1625-1759
• + 80k births studied
o Miscarriages and still births omitted (Obstetric problems)
o Infants dying within 28 days of birth omitted (Inherent viability problem)
o To rule out cross-infection children dying less than 2 weeks after the mother were omitted.
o Correction for ‘between family effects’ i.e. tendency for some mothers and their children to both be vulnerable to death
• Child mortality levels before a mother’s death were computed and used to adjust the odds ration for child mortality after the mother’s death.
• Found that if mother died neonatally the child was 5x more likely to die within first year if mother died postneonatally 4x likely for child to die in first year. Mother dies past this about 2.5x more likely to die being a toddler or early childhood. So bad, but particularly bad for early life


Data comparing influence of losing a mother versus a father

Ache data
We do see a drop relative for dads but way bigger for the mother Hurtado and Hill.


Data comparing influence of losing a mother versus a father

Ache data
We do see a drop relative for dads but way bigger for the mother Hurtado and Hill.