Discuss the role of neural and/or hormonal mechanisms in aggression.
There is a circuit of brain structures involved in aggression running form areas of the amygdala, down to the hypothalamus, and from there to the PAG. This system is organised in a hierarchical way, so aggressive responses originating from higher up in the circuit depend on the normal function of structures below. For example, aggressive responses from the amygdala rely on normal functioning of the hypothalamus and PAG. Research has shown the involvement of the limbic system in aggression but more recent research has shown involvement of the amygdala and prefrontal cortex.
Electrical stimulation of amygdala produces aggressive behaviour in both animals and humans. Wong et al found reduced amygdala size and activity in violent animals. However, other researchers have not found this and so these contradictory findings question the validity of the research. The prefrontal-cortex is thought to regulate amygdala-driven emotional responses and damage here can result in loss of control, impulsivity and immaturity. Anderson et al found that damage to the prefrontal-cortex in infancy leads to an increased risk of aggressive behaviour as adults, and the risk is greater than in people with adult onset damage. This is due to the negative influence of brain damage on social development. A real life example, Phineas Gage, was involved in an accident where a pole went through the front of his brain and this resulted in him displaying more aggressive behaviour.
Aggression occurs more often in males than females and this is usually attributed to the male sex hormone testosterone. Castration is used to make domestic animals more manageable as it reduced testosterone levels.Beeman castrated male mice and found reduced levels of aggression. He re-established normal levels of aggression by giving the mice injections of testosterone. Castration should be done before puberty, before aggressive behaviour is established. Also VomSaal found female rates that occupied spaces in the womb closest to males were the most aggressive as they were exposed to more testosterone. This supports the idea that testosterone causes aggression. It’s difficult to compare animal research to human research as humans brains are more evolved and humans live more complex lives in a complex environment. Additionally, there are ethical issues with the testing of animals for research.
Dabbs et al investigated the relationship between testosterone, crime and prison behaviour and those who had committed sexual and violent crimes had the highest levels of testosterone. These prisoners were more likely to be the most confrontational prisoners. Another study Dabbs carried out was where he measured testosterone levels in female inmates and this was positively related to unprovoked violence. Other researchers have not found this which highlights the problem of operationalizing aggression. Furthermore, Pillay found that male and female athletes in high-ranked aggressive sports had higher levels of testosterone.
The problems with this research is the variability in the findings and so it’s difficult to compare the findings, and it questions the validity. Research is correlational and so cause and effect cannot be established. Also, measuring levels of aggression is unreliable as behaviour is open to interpretation. There are many other reasons for why aggression occurs other than neural and hormonal factors. This theory does not take into account environmental factors such as deinvididuation and so it could be argued that it’s a reductionist theory. In addition this type of research is socially sensitive and so it lessens the guilt and reduces responsibility for aggressive behaviour. Individuals can ‘blame’ hormone levels/ brain structures as a reason to display aggressive behaviour. Lastly, there are ethical issues of psychological and physical harm to animals during research e.g. the mice were castrated in Beeman’s study. It may be seen as morally/ethically wrong.