Neural & hormonal mechanisms

• Outline the role of the amygdala in neural mechanisms to aggression.

  Limbic system:

  -papez & maclean linked limbic system to emotions(e.g. aggression)

  -system included hypothalamus, amygdala, & parts of hippocampus

  -amygdala → more reactive amygdala is to environmental threats= more aggression shown

  -gospic et al → used fMRI with ppts in lab-based game that provoked aggression

  aggressive reactions associated with fast & heightened response by amygdala

  -benzodiazepine (reduces arousal of ANS) taken before game decreases amygdala activity & decreases aggression
• Outline OFC & serotonin in neural mechanisms to aggression.


  OBC = low levels of ↑ aggression

  • normal levels of serotonin in OBC inhibit neurons (reducing firing) & are linked to ↑ behavioural self-control
  • ↓ serotonin disturbs mechanism, ↓ self-control & ↑ impulsive behaviours (e.g aggression) - Denson et al
  • Virkukuken et al → found lower levels of serotonin metabolite 5-HIAA in violent impulsive offenders compared with non-impulsive offenders
• Strength to neural mechanisms on aggression

  ✓:research into effects of drugs on serotonin - Berman et al

  -ppts took part in lab-based game, giving and relieving electric shocks in response to provocation
• Limitation to neural mechanism to aggression

  X: non-limbic brain structures are also involved

  -limbic structures function jointly with the non-limbic OFC

  -this is involved in impulsive-regualtion and inhibition of aggression

  -Coccaro et al = claim OFC activity is reduced in psychiatric disorders featuring aggression - this disrupts OFC ‘s impulse-control function, increasing aggression

  -shows neural regulation of aggression is more complex than theories focusing on the amygdala suggest
• Outline role of testosterone in hormonal mechanisms in aggression

  Testosterone = helps regulate social behaviour via influence on brain areas involved in aggression

  -males are more aggressive towards other males a 20+ yrs (when testosterone levels peak)

  -Dolan et al → found +ve correlation between testosterone and aggression in male offenders with histories of impulsively violent behaviour

  -Giammanco et al → animal studies linked show aggression linked to testosterone

  -castration studies (removing testes) reduces aggression in many species, injecting testosterone restores aggressive behaviour
• Outline the role of progesterone in hormonal mechanisms for aggression

  Progesterone = female sex hormone

  -low levels linked to aggression in women

  -progesterone levels vary in menstrual cycle (lowest after menstruation)

  -negative correlation between progesterone levels and self-reported aggression
• Strength of hormonal mechanisms



  ✓: research with non-human animals

  -Giammanco et al’s review confirms role testoserone (e.g. increase in testosterone) and aggression in male monkeys during mating season

  -in rats, castrations of males reduces testosterone and mouse-killing, and injecting female rats with testosterone increases both testosterone and mouse-killing = findings show testosterone plays key role in aggression
• Limitation of hormonal mechanisms

  X: evidence linking testosterone & aggression is mixed

  -Carre & Mehta’s dual hormone hypothesis suggests high levels if testosterone lead to aggression but ONLY when cortisol levels are low

  -high cortisol blocks testosterone’s influence on aggression

  -cortisol = hormone that is key to body’s hormone that is key to body’s chronic stress response

  -combined activity of testosterone & cortisol may be a better predictor of aggression than either hormone alone
• Another limitation to hormonal mechanisms

  X: animal research

  -aggression is a complex behaviour than in other mammals

  -animals studied can be applied and generalisable to an extent