Topic Summaries

Neural and hormonal mechanisms in aggression

A-Level > Psychology > AQA > A-Level Psychology Topic Summaries > Aggression > Neural and hormonal mechanisms in aggression
Previous Module
Next Module

Addiction

  • There are two types of aggression: proactive aggression: when someone deliberately plans to hurt someone to get what they want (e.g. premeditated murder), and reactive aggression: unplanned, impulsive aggression when people are angry (e.g. road rage).
  • Neural mechanisms: the limbic system contains multiple components, including parts of the hippocampus, the hypothalamus, and the amygdala. The amygdala has a key role in how humans and animals assess and respond to environmental threats. The reactivity of the amygdala has been shown to be a good predictor of aggressive behaviour.
    • 👥 Gospic’s (2011) lab study used fMRI scans to measure brain activity during a game called the Ultimatum game between two players where one is the prosperor and one is the responder. The prosperor offers to split money with the responder. If the responder rejects the offer, then they both get nothing. The results showed heightened arousal in the amygdala when the offer was rejected, suggesting aggression.
  • The role of serotonin:
    • Serotonin is a neurotransmitter that regulates mood and is involved in the communication of impulses between the neurons. It has an inhibitory effect on the brain as it slows and dampens neural activity. Low levels of serotonin reduce self-control and increase impulsivity. Drugs that increase serotonin levels have been shown to reduce aggression.
    • In recent studies it’s been shown that the amygdala functions alongside orbitofrontal cortex, not in isolation. This isn’t involved in the limbic system, but plays a role in regulating mood and self-control. Therefore, the regulation of the amygdala is highly complex and can’t just be put down to the amygdala alone.
    • 👥 Virkkunen (1990) examined the breakdown products of serotonin in criminals’ cerebrospinal fluid. He compared violent, impulsive criminals to violent, non-impulsive criminals and found that the levels were significantly lower in impulsive criminals
  • Hormonal mechanisms in aggression:
    • Testosterone is the male sex hormone and plays a role in regulating social behaviour. Generally, males tend to be more generally aggressive, and animal studies have shown a link between an increase in testosterone and a rise in aggression.
    • 👥 Dolan (2001) found a positive correlation between testosterone levels and aggressive behaviour in 60 male serious offenders in high security prisons in the UK.
  • Genetic factors:
    • Twin studies: suggest that heritability is responsible for about 50 % of the variance in aggression. 👥 Coccaro (1997) found concordance rates of 50 % for MZ twins and 19% for DZ twins regarding physically aggressive behaviour. The figures for verbal aggression were 28% for MZ twins and 7% for DZ twins. However, a problem with using twin studies is that their behaviour may be influence by their environment.
    • The MAOA gene: MAOA is an enzyme that aids in recycling serotonin by mopping up leftover neurotransmitters after a nerve impulse, breaking down serotonin to be cycled or excreted. People who have dysfunctional MAOA genes have abnormal serotonin levels (i.e. low enzyme = low serotonin = impulsive behaviour and aggression).
    • This is supported by 👥 Brunner (1993) who studied 28 male members of a Dutch family who were consistently involved in violent and aggressive behaviour and found that each had low levels of the MAOA enzyme in their brain. 👥 Stuart (2014) also studied 97 men who had been convicted of domestic violence and found the men who committed the most violent abuse had the low activity version of the MAOA gene.

Unlock Neural and hormonal mechanisms in aggression

Subscribe to SnapRevise+ to get immediate access to the rest of this resource.

Premium accounts get immediate access to this resource.

Previous Module
Next Module