Throughout history aggression has been the cause of much sorrow for humanity, often resulting in institutionalisation and social ostracisation for the aggressor; and trauma or even (in extreme situations) fatal injuries for the victim. The Oxford English Dictionary defines aggression as ‘feelings of anger or antipathy resulting in hostile or violent behaviour; readiness to attack or confront’. The prevention of aggressive behaviour has been the subject of extensive research – but to prevent aggressive behaviour, we must first understand the cause. Some theories put forward to suggest the cause of aggressive behaviour focus on biological causes, which include genetics, hormonal mechanisms and neural mechanisms. Other theories suggest that aggression is, in fact, caused by social and environmental factors, such as deindividuation and social learning theory.
Social learning theory (SLT) is commonly proposed by behaviourists to explain aggression. SLT suggests that all behaviour, including aggression, is learned either by direct or vicarious experience. A person can learn through direct experience, according to SLT, if their behaviour is reinforced, for example, if violent behaviour leads to positive outcomes (or ‘rewards’) for the aggressor, they may be encouraged to do it again. Moreover, aggressive behaviour can be learned vicariously through observation, for example, a child seeing and then imitating violence.
Bandura et al. 1963 attempted to prove how social learning theory can explain aggression in their experiment. They divided nursery school children into three groups, all of whom saw a video of an adult demonstrating aggressive behaviour towards a Bobo doll. In the first condition, the film ended there. In the second condition, the children were shown an additional video of the adult being rewarded for his aggressive behaviour. In the third condition, the adult was seen to be punished for his aggressive behaviour. The children were then filmed with the Bobo doll. Those in the first and second condition were markedly aggressive towards the doll, with the second condition being significantly more aggressive than the first, whereas, the children in the third condition tended to not be aggressive towards the doll. This demonstrates behaviourist psychologist B.F. Skinner’s principles of operant conditioning (learning by reinforcement), as the children who behaved with the most aggression were those who observed the adult being ‘rewarded’ for his behaviour, and the children who behaved with the least aggression were those who observed the adult being ‘punished’ for his behaviour. Bandura’s experiment also demonstrates learning vicariously, as the children in the first conditions were aggressive after merely observing the same behaviour.
Social learning theory, therefore, can offer us a plausible explanation of aggressive behaviour. However, it presents act of aggression as simple mimicry, which provides us with no understanding of exactly how the behaviour is learned. Moreover, it places no control over aggressive behaviour with the individual, instead, an external source must be present to create the aggression. Social learning theory can, therefore, offer a valid explanation as to why aggression occurs, but not how it can be avoided by the individual.
Social psychologists have proposed deindividuation as an explanation for aggressive behaviour. When deindividuation occurs, people lose their sense of identity and socialisation. As what is, and what is not, acceptable in society results from socialisation, when our sense of this is lost, social psychologists suggest that it can lead us to act in a more ‘primitive’ manner, which is where aggression occurs. Moreover, putting on a uniform or being part of a very large crowd can cause us to lose our sense of individuality, as we now feel that we are simply part of a group, and not an autonomous being and, subsequently, we are more susceptible to committing aggressive actions.
Anthropologist Watson (1973) hypothesised that tribal warriors who changed their appearance significantly (and who where, therefore, the most deindividuated), would be more likely to kill and torture their opponents than those who did not. He studied 23 societies, 13 of whom were especially brutal. In these 13 societies, all but one changed their appearance and were, subsequently, deindividuated, whereas, in the 10 less violent societies, seven on the ten societies did not change their appearance, and so had not undergone the process of deindividuation.
Deindividuation has many merits as an explanation for aggression. It can be seen in everyday society, such as in football hooliganism and rioting, whereby, people may feel more able to commit violent acts as they are simply part of a crowd. However, deindividuation can be criticised as an explanation for aggression. Social psychologists suggest deindividuation occurs within a person is in a crowd, as it removes their sense of identity and, therefore, causes them to act in an antisocial manner, although, it is group behaviour that usually encourages conformity and social behaviour, suggesting that the very same scenarios that cause us to learn norms and values also strip us of them.
Membership of certain institutions has also been blamed for aggressive behaviour, particularly prisons. The importation model, put forward by Irwin and Cressey (1962) suggests that violence occurs within prisons because the type of person most likely to enter such an institution is predisposed to violent behaviour within that institution due to the experiences they have had in life that put them there. The deprivation model turns the importation model on itself, and suggests that the institution itself is most to blame for escalating violent behaviour due to the frustration resulting from the loss of personal freedoms inmates experience whilst there.
One of the most controversial experiments in the history of psychology, the Stanford Prison Experiment (Zimbardo et al. 1973) demonstrated institutional aggression. For the experiment, Zimbardo created a mock prison and recruited students to assist. Some of these students were told to play the role of guards, whilst the others were told to act as prisoners. Both groups were given relevant uniforms and the prisoners were referred to only by their assigned number. The prison setting, along with the deindividuation of the inmates and guards upon entry, caused the experiment to become violent, so much so that the experiment was terminated after six days out of the intended fourteen.
Institutionalisation into prisons is a possible explanation of aggression. However, it does not explain the aggressive behaviour that initially leads to institutionalisation, much like the importation model suggests. Moreover, it does not explain why aggression exists outside such institutions – not all violent actions are reported to the police, and those that are do not necessarily result in prison sentences.
Biological psychologists offer alternative explanations of aggression to social and behaviourist psychologists. Instead of pointing towards the environment an individual is in as the cause for aggression, they instead claim that violence can stem from genes, hormonal mechanisms and neural mechanism. The neurotransmitters dopamine and serotonin in particular have been linked to aggression when levels of the former are high, and levels of the latter are low. Dopamine has been linked to aggression due to it’s association with pleasure. It is the neurotransmitter stimulated after eating certain foods or sexual intercourse, and has been found to become more abundant after violent behaviour. Therefore, the ‘reinforcing’ nature of dopamine could cause violent behaviour. Increases in dopamine activity have also been shown to increase aggression, as evidenced in the use of amphetamines, which stimulate dopamine. Serotonin’s function in the brain is to inhibit the firing of other neurons, especially in the prefrontal cortex, which is the area in our neuroanatomy responsible for cognitive reasoning and social behaviour, among other things. It is the area where our morals are reasoned and the consequences of our actions are considered.
Evidence for the roles of serotonin and dopamine in aggressive behaviour comes from Ferrari et al. (2003). In their experiment, they allowed a rat to fight at the exact same time every day for ten consecutive days. On the eleventh day, at the time the rat was due to fight, they measure its dopamine and serotonin levels, and found the former to be high, and the latter to be low. This demonstrates that the mere anticipation of a fight was enough for the rats adjust its brain chemistry.
Neural mechanisms have an undeniable link to aggression. However, it is difficult to determine causation – if that rat in Ferrari’s experiment changed its brain chemistry in anticipation of a fight, it may be that this is a physiological adaptation, designed to make the rat more likely to survive, rather than the rat being aggressive in the first instance due to the varying levels of neurotransmitters. Therefore, it could be aggression causing high levels of dopamine and low levels of serotonin, rather than neural mechanisms causing aggression.
Hormones such as testosterone and cortisol are also frequently linked with aggressive behaviour. Although the role testosterone plays in aggression is not absolutely clear, it has been suggested that it can inhibit activity in the orbitofrontal cortex in the brain, which controls impulsivity, causing the aggressor to have reduced control over their actions. Inversely, the hormone cortisol is shown to combat aggression and, therefore, insufficient levels of cortisol can cause aggressive behaviour. Cortisol is released into the blood stream as part of the body’s response to chronic stress, and assists the regulation of glucose levels in the body, which has a calming effect. If an inadequate amount of cortisol is released, a person’s body may fail to stabilise its sugar levels when exposed to stress, which can cause them to become aggressive.
The impact of hormonal mechanisms on aggressive behaviour is supported by the research of Book et al. (2001) who found a correlation of +0.14 between testosterone and aggression after carrying out a meta-analysis of 45 studies. Similarly, a study performed by McBurnett et al. (2000) found that boys with behavioural difficulties were three times more likely to display aggressive symptoms if their cortisol levels were low.
While there is some evidence in favour of hormonal mechanisms as an explanation for aggression, there is a lot of contradictory evidence which suggests otherwise. Kreuz and Rose (1972) studied prisoners, some of whom were known to be frequently involved in fights, whilst others were not. They found no significant difference in testosterone levels between the prisoners who fought, and prisoners who did not, suggesting that testosterone does not play an important role in aggressive behaviour. Similarly, Gerra et al. (1997) found a positive correlation between cortisol and aggression, which suggests that cortisol may not have a subduing effect on aggression, and instead it may aggravate the problem.
Behavioural genetics is also frequently put forward as a biological explanation for aggression. A lot of research involving genetics utilises twins, as this allows the researcher to determine whether a person’s genotype has caused aggression, or if it was caused by interaction between genes and the environment. Research has also been focused on adopted children with at least one biological parent known to engage in aggressive or antisocial behaviour, to determine whether they developed the same traits as their parents, irrespective of growing up in the same environment as them.
McGuffin and Gottesman (1985) studied aggression and compared monozygotic (identical) twins and dizygotic (fraternal) twins and found a concordance rate of 87 percent for aggression in monozygotic twins, compared with 72 percent in dizygotic twins. As monozygotic twins share all of their genes, whereas dizygotic twins only share half of their genes, this suggests that genes play a large role concerning aggressive behaviour. Similarly, Hutchings and Mednick (1973) studied 14,000 adopted children in Denmark and found a positive correlation between convictions for violent behaviour amongst biological fathers, and convictions for violent behaviour amongst their sons, who had been adopted. This is evidence for the role of genes in aggression, as the adopted sons engaged in violent activity, despite being removed from their violent fathers.
Whilst there is obviously strong evidence supporting genetics as an explanation for aggression, it is unlikely that a person’s genotype alone is responsible for aggressive behaviour – instead, it is more likely that aggression arises from interaction between genes and the environment. The gene monoamine oxidase A (MAOA), in particular, has been the focus of research regarding gene-environment interaction and aggression. MAOA is otherwise known as the ‘Warrior gene’ and is known to positively correlate with violent behaviour. Caspi et al. (2002) found that children who had been mistreated, and who possessed the MAOA gene, were more likely to express that gene (and, thus, engage in aggressive behaviour) as a result, whereas, children who possessed the gene but were not abused were less likely to express the gene and become aggressive.
It is frightening to think that there is a possibility aggression may be written in our DNA and biochemistry, and that we have little ability to exercise free will to combat it. However, I don’t believe we can categorically conclude that aggression is caused by biological factors alone. Similarly, I don’t believe deindividuation, social learning theory or institutionalisation universally explain the cause of aggression. Whilst they all have merits as theories, and whilst it is evident that genetics and physiology can influence aggressive behaviour, I believe that the human experience is far too broad and full of trepidation for there to be one sole cause for aggressive behaviour.
staceyav 