Aggression

• The limbic system is the network of subcortical structures in the brain (including the hypothalamus, hippocampus and the amygdala) thought to be closely involved in regulating emotional behaviours such as aggression.
• Amygdala: responsible for the response to environmental threats and challenges, Gospic et al- used the Ultimatum game , the prosper offers to split the money in a certain way with the responder, if the responder accepts the money is split if they reject they get nothing, when rejecting Reponses their was a fast and heightened response from the amygdala. If participants took a benzodiazepine drug then it halved the number of rejections and decreased activity of the amygdala.
• Coccaro et al. (2007) found that patients with psychiatric disorders that feature aggression had reduced activity in the OFC. This has been found to disrupt impulse control function and consequentially lead to increased aggression.
• Decreased serotonin may well disrupt the brain mechanism, reducing self-control and leading to an increase in impulsive behaviour, including aggression (Denson et al. 2012).
• Berman et al. (2009) gave patients either a placebo or paroxetine - a drug which enhances serotonin activity. Those who took the drug consistently gave fewer and less intense shocks than those in the placebo group (only true of the patients who had a prior history with aggression)
• Giammanco et al. (2005), have demonstrated that increases in testosterone are related to greater aggression in several species.
• • Dolan et al. (2001) studied a sample of 60 male offenders in UK maximum-security hospitals.
  • They found a positive correlation between testosterone levels and aggressive behaviours.
• Carre and Mehta (2011) developed the dual-hormone hypothesis. This claims that high levels of testosterone leads to aggressive behaviour only if levels of cortisol are low. When cortisol is high, testosterone’s influence on aggression is blocked.
• Coccaro et al. (1997) studied aggressive behaviour (defined as direct physical assault) in adult male MZ and DZ twins. They found concordance rates of:

  • 50% for MZ twins.
  • 19% for DZ twins.
• Rhee and Waldman (2002) carried out a meta analysis of adoption studies relating to direct aggression and antisocial behaviour. They discovered that genetic influences accounted for 41% of the variance in aggression.
• The MAOA gene codes for the MAOA enzyme which is used to 'mop up' the neurotransmitter left in the synapse. Brunner et al investigated how a variant of the MAOA gene affected a Dutch family who were repeat offenders, 28, they all had abnormally low levels of the MAOA gene in their brains.
• GxE interactions ( gene-environment) low levels of MAOA only seem to influence aggressive behaviour when there is a early traumatic life event. Frazzetto et al, found an association between high levels of aggression and low MAOA gene when the person had a significant life trauma before they were 15.
• Issues with studies investigating aggression: methodological issues - there is not a set way to measure aggression which means there are significant differences between how different studies measure aggression, types of study - normally lab or self-report so issues with validity
• Ethological explanations attempt to understand the innate behaviour of human and non-human animals by studying them in their natural environment. Aggressive behaviour with animals is seen as adaptive (beneficial for survival.)
• • Pettit et al. (1988) studied groups of young human children and observed how aggression played an important role in the development of some children’s dominance over others.
  • This is adaptive because dominance over others brings benefits such as the power to get your own way and access to resources.
• Nisbett (1993) compared homicide rates in different parts of the United States .He found a north-south divide. Killings were much more common amongst white males in the southern states than the northern states but only for reactive aggression triggered by arguments. Culture has an impact not just genetics
• An innate releasing mechanism is a built-in physiological process or structure, for instance a network of neurons in the brain. An environmental stimulus triggers the IRM which then releases a specific sequence of behaviours called a fixed action pattern, or FAP. Lea identified six key features :Stereotyped, Universal, Unaffected by learning, ballistic, single purpose, a response to an identifiable specific sign stimulus
• Tinbergen found that during the sticklebacks mating season the male sticklebacks would attack each other and they could be identified as they had a red dot on their stomachs, he found that the sticklebacks would still attack a wooden object even if it had the red dot but wouldn't attack a fish resembling the male stickleback if it didn't have the red spot, the FAPs were fixed during the attacked, and they would always run their full course.