Neural & Hormonal Mechanisms in Aggression

• Who linked the limbic system to emotional behaviour?

  Papez and Maclean
• What is the limbic system thought to regulate?

  Emotional behaviour
• What structures are included in the limbic system?

  • Hypothalamus
  • Amygdala
  • Parts of the Hippocampus
• What is the role of the amygdala in aggression?

  Predictor of aggressive behaviour
• How does amygdala responsiveness relate to aggression?

  Higher responsiveness leads to more aggression
• What did Gospic et al (2011) study involve?

  Participants subjected to mild provocation
• What did fMRI scans reveal during aggressive reactions?

  Fast response by the amygdala
• What effect does benzodiazepine have on aggression?

  Reduces amygdala activity and aggression
• How is serotonin linked to self-control?

  Normal levels promote greater self-control
• What happens when serotonin levels decrease?

  Reduces self-control and increases impulsivity
• What did Virkkunen et al (1994) compare in their study?

  Serotonin breakdown product levels
• What was found about impulsive offenders' serotonin levels?

  They had significantly lower levels
• What is the effect of drugs that increase serotonin?

  • Reduce aggressive behaviour
  • Evidence of a causal link with aggression
• What did Berman et al (2009) study involve?

  Participants in a lab-based game
• What was the outcome for the drug group in Berman et al's study?

  Gave fewer and less intense shocks
• How do limbic structures interact with the orbitofrontal cortex?

  They function together in impulse regulation
• What role does the orbitofrontal cortex play?

  Inhibition of aggressive behaviour
• What is testosterone linked to?

  Aggressive behaviour
• When do men become more aggressive towards other men?

  When testosterone levels are highest
• What do castration studies show about testosterone?

  Reducing testes reduces aggression
• What happens when testosterone is injected into castrated animals?

  Aggressive behaviour is restored
• What role does progesterone play in aggression in women?

  Low levels are linked to increased aggression
• What did Ziomkiewicz et al (2012) find about progesterone levels?

  Negative correlation with self-reported aggression
• What does Giammanco et al (2005) review confirm?

  • Role of testosterone in aggression
  • Observed in various animal species
• What is the dual-hormone hypothesis proposed by Carré & Mehta (2011)?

  Testosterone affects aggression when cortisol is low
• How does the dual-hormone hypothesis improve understanding of aggression?

  Combines effects of testosterone and cortisol
• What is a strength for the Neural Mechanisms of Aggression?

  Drugs & Serotonin

  • Drugs that increase serotonin have been found to reduce levels of aggressive behaviour
  • Berman et al (2009) had participants either take a placebo or a dose of the drugs, and then take part in a lab-based game that involved giving and receiving electric shocks in response to provocation and the group that was given drugs consistently gave fewer and less intense shocks
  • This study is evidence of a causal link between serotonin function and aggression
• What is a limitation for the Neural Mechanisms of Aggression?

  Other Brain Structures

  • Limbic structures function together with the orbitofrontal cortex, which is not part of the limbic system
  • The orbitofrontal cortex is involved in impulse regulation and inhibition of aggressive behaviour
  • This suggests that the neural regulation of aggression is more complex than theories focusing on the amygdala suggest
• What is a limitation for the Hormonal Mechanisms of Aggression?

  Dual-Hormone Hypothesis

  • Carré & Mehta (2011) developed a dual-hormone hypothesis to explain why there is mixed evidence of the link between testosterone and aggression in humans
  • They claim that high levels of testosterone lead to aggressive behaviour but only when levels of cortisol are low
  • Therefore, the combined activity of testosterone and cortisol may be a better predictor of aggression than either hormone alone
• What is a strength for the Hormonal Mechanisms of Aggression?

  Animal Research

  • Giammanco et al (2005) review of studies confirms the role of testosterone
  • For example, in male rhesus macaque monkeys, there is an increase in both testosterone levels and aggressive behaviour during the mating season
  • These findings show the role of testosterone in a range of animal species