Research from a variety of numerous psychologists has contributed to proving the role of neural and hormonal mechanisms in aggression. Phineas Gage survived for a serious accident which left serious damage to his amygdala, although 11 years after there were noticeable changes to his personality. He went from being a happy and kind man to a cold and aggressive man, proving that damage to the amygdala is associated with aggression. However, the study lacks population validity and reliability as it is based on one individual. Raleigh et al conducted an experiment of vervet monkey to further support the association with serotonin and aggression. They fed a certain amount monkeys on experimental diets that were high in tryptophan (which is known to increase serotonin levels) and found a decrease in the levels of their aggression. The other monkeys in the experiment were fed on diets of low levels of tryptophan and exhibited increased levels of aggression. This supports the role of serotonin on aggression because it shows the lower levels of serotonin are correlated with higher levels of aggression. Further support comes from Screbo and Raine (1993), who did a meta-analysis of 29 studies. They examined neurotransmitter levels in antisocial children and adults. They found that lower levels of serotonin in individuals who were described as aggressive. This suggests that serotonin depletion leads to impulse behaviour, which can lead to aggressive behaviour, therefore supporting the link between serotonin levels and aggression.
A critique of neural mechanisms as an explanation of aggression could be that it raises issues of extrapolation due to non-human animals used in experiments such as the findings on serotonin replicated in vervet monkeys. Can the findings really be generalised to humans? The nature and mentality of animals is much different to humans. Also this study faces ethical issues as the vervet monkeys faced irreversible mental changes that could have been avoided if the experiment was not conducted. Because of this the experiment would not be able to take place in modern society. However Lenard (2008) explained that serotonin is not just linked to aggression. It is also linked to: impulsive behaviour, depression, over eating, alcohol abuse; violent suicide. Exaggerating the role of these neutral and hormonal mechanism leads to a deterministic view of people’s actions. Zimbardo quotes, ‘Psychology is not excuseology’. Peoples actions can be blamed on the mechanisms which is immoral as these individuals should be taking responsibility for their own actions and face the consequences. There have been court cases where the sentence has been reduced because the perpetrator has claimed hormonal imbalance as responsible for their actions. This can be further criticised due to the reductionist view towards the biological approach, it is psychologically reductionist to consider that such a complex phenomenon can be explained by levels of biochemical. It is important to also consider genetic factors, brain structure and the contribution of environmental factors such as situational cues, temperature, noise, overcrowding and the role of learning.
The Causal role of dopamine and testosterone is still unclear. It is a possibility that high levels of dopamine and testosterone are an effect rather than a cause. There is evidence conflicting the role of aggression that expresses that testosterone does not cause aggression but exaggerates aggression that is already there. Many of the studies are mainly correlational, for example Wagner’s, so it is not possible to conclude that testosterone causes aggression. Human studies suggest testosterone rises as aggression rises (Lindman et al’s study of drunken males). On the other hand, it may be that testosterone does not increase aggression but that it depends on how physiological responses are interpreted, in animals it may be testosterone increases dominant behaviour. Studies have proven that not just negative factors come from high levels of testosterone; Huston found that men with high levels of testosterone perform well on competitive tasks and low on co-operative tasks. However it is predicted that these sorts of males are also likely to take part in anti-social behaviour in order to be more dominating not aggressive. Gender bias in this biological approach is evident as most research is done on males, both humans and non-humans. This leaves the question of ‘is there no relationship between levels of testosterone and aggression in women’ unanswered.
Clearly a very important and useful area of bio-psychological research is associated with many anti-social acts in society such as numerous forms of crime including violence. If the role of biochemistry can be understood it can perhaps be treated or managed. However, it is unethical to give drugs to humans to simply alleviate aggression as this debatably could lead to social control. In conclusion there is a possibility this could be treated more ethically through diet and exercise which acts on neural mechanisms.