Aggression

Genetic - twin and adoption studies - AO1

aggression is heritable by about 50%
Coccaro - physical assault: 50% MZ, 19% DZ. verbal: 28% MZ, 7% DZ
similar in adoption studies: meta analysis by Rhee and Waldman: 41% genetic influence

Genetic - Genes - AO1

MAOA gene produces enzyme called MAO-A. Breaks down serotonin at end of day. Nicknamed warrior gene.
low activity means not enough cleaning of serotonin: high serotonin. Make’s a person more receptive to stress: will respond with fight during fight or flight

Brunner - Genetics

28 men from a large Dutch family who had been involved in various aggressive criminal acts such as rape, attempted murder, physical assault. They had abnormally low levels of enzyme MAO-A

Frazzetto - Genetics

diathesis stress: those who had low MAOA activity would only be aggressive if they had had severe trauma in first 15 years of life - 1/3 of men have this gene, so not purely genetic - nomothetic vs idiographic

AO3 - Genetics - Research

knockout mice where MAOA was knocked out showed higher serotonin and more aggressive behaviour, but when Fluoxetine (serotonin inhibitor) was administered, returned to original behaviour

AO3 - Genetics - General

Twin studies: equal environments assumption
Nature versus Nurture: genes are not a direct cause
Neural: low serotonin can cause aggression as unable to inhibit aggressive impulses from amygdala at orbitofrontal cortex - at odds with each other

AO1 - Neural - limbic system

hypothalamus, amygdala, parts of hippocampus
reactivity of amygdala is a predictor of aggressive behaviour.
orbitofrontal cortex controls behaviour to prevent amygdala impulse

AO1 - Neural - Orbitofrontal Cortex and Serotonin

serotonin has an inhibitory effect → slows/calms neuronal activity. Greater behavioural self-control when normal levels of serotonin in orbitofrontal cortex. More impulsive when deficiency of serotonin.

AO1 - Hormonal - Testosterone

Increased testosterone is associated with aggression
mice research implicates aromatase, an enzyme which metabolizes testosterone: deficiency of the enzyme → testosterone increases reactivity of aggression
testosterone reduces orbitofrontal cortex activity allowing amygdala to have more response
testosterone reduces serotonergic activity.

AO1 - Hormonal - Progesterone

aggression in women. vary during ovulation cycle, lowest during/after menstruation. negative correlation between progesterone levels and self reported aggression

AO3 - Hormonal - general

Any biological explanation is biologically reductionist - human aggression based on many factors vs animals which are simple (humans multifaceted) ~ caution should be taken when extrapolating from animal research

Beta Bias - studies involving testosterone and aggression center around men as opposed to women despite women having testosterone (androcentric sample)

Socially sensitive - this has ramifications for the legal system and ethics as it suggests men are not responsible for their behaviour if they have high testosterone (can also be considered biologically determinist)

Testosterone inhibiting drugs may be able to be used to treat high levels of aggression, diet changes such as less alcohol to reduce amplification of testosterone/serotonin

AO3 - research - neural

Wong - MRI scans of 19 violent male criminals in one hospital, compared with 20 controls, found they had significantly smaller amygdalas
|CP: androcentric → beta bias, small sample size, correlational
Raine - PET scans showed murderers who had pleaded not guilty had reduced activity in orbitofrontal cortex
Ferrari - everyday encouraged rats to fight at a time, on 11th were not allowed to, dopamine up by 65%, serotonin decreased by 35%
contradicting evidence → genetic explanation suggests high serotonin results in aggression
Virkkunen - compared 5-HIAA in cerebrospinal fluid of violent impulsive/non-impulsive offenders. Much lower in impulsive offenders

AO3 - Neural - General

free will vs biological determinism → socially sensitive and takes away from guilt
reductionist → ignores sociocultural factors

AO3 - Hormonal - Research

Dolan - positive correlation between testosterone levels and aggressive behaviours in 60 male offenders in UK max security hospitals. they had personality disorders and histories of impulsive violent behaviour
Dabbs - took saliva swabs of inmates who were in prison for either violent/nonviolent crimes. Salivary testosterone was significantly higher in those who had committed violent crime
Connor/Levine - young rats when castrated showed lower aggression, however, this did not work on fully developed rats. therefore link between testosterone and development is linked to aggression

AO1 - Ethological - Innate and Adaptive

aggression is adaptive → establish dominance hierarchies, those more dominant have more resources
ritualistic aggression → in same species, there is mostly signaling (displaying claws), little damage, signaling of defeat (appeasement display) e.g. wolves expose neck to victor, and defeated individual looks for new territory. Not normally killed. Prevents species extinction via competition and allows species to spread over wider area preventing competition

AO1 - Ethological - Releasing Mechs

innate releasing mechanisms are triggered by stimulus → cause neural activation → then specific sequence of behaviours called Fixed Action Pattern:
- stereotyped
- universal
- unaffected by learning
- ‘ballistic’
- single purpose
- a response to an identifiable specific sign stimulus

AO1 - Ethological - Tinbergen

male sticklebacks are very territorial during mating season and develop a red spot on their underbelly. A FAP of aggressive behaviour is when a male enters their territory, the sign stimulus is the red spot on another male.
Tinbergen displayed wooden models, if they had a red spot the sticklebacks would show aggressive display/attack it, but if no red spot no aggression. The FAP changed from one encounter to another (universal) and always ran to completion without any further stimulus (ballistic)

AO3 - Ethological - Research

Goodall - ‘4 year war’ of chimps, chimps held down by opposing group and hit for several minutes despite appeasement signals, so not ritualistic
Nisbett - in a lab experiment, South American white males were insulted they were more likely to respond aggressively than white North American males under the same conditions, due to culture of honour
Gospic → neural mechs (IRM)
Brunner → Strength as shows aggression as genetically determined, heritable, adaptive

AO3 - Ethological - General

Individual differences (idiographic) - aggression in Amish community is very low, aggression should be uniform across all countries as innate
FAPS actually influenced by learning - duration of each behaviour in sequence differs per individual, modifiable experience, so ‘modal behaviour pattern’ is more appropriate e.g. training dogs to not chase, or breeds not choosing to chase