The structure of the brain, different brain areas including the pre-frontal cortex and limbic system and brain functioning as an explanation of aggression as a human behaviour.
The main neural explanation is limbic theory involving structures such as the amygdala, hypothalamus, and hippocampus which are implicated in reactive aggression. Reactive aggression is a response to a perceived threat, rather than proactive aggression which is a response in anticipation of a reward. The limbic system also connects to the cingulate gyrus which is responsible for focusing attention on emotionally significant events. Also, the limbic system has connections to the prefrontal cortex which is involved in forward planning and anticipation of reward. The limbic system plays a key role in how an organism responds to environmental threats and challenges and thus is believed to be the key factor in whether we respond aggressively or not to an external stimulus.
The hypothalamus is responsible for the regulation of the autonomic nervous system, which in turn regulates responses to emotional circumstances. Therefore, damage to this area can result in an inappropriate aggressive response to a perceived threat. The limbic system includes the amygdala which is said to be responsible for emotional reactions so if this is over active it could cause aggression.
The pre-frontal cortex plays a role in controlling behaviour and delays gratification of impulses. If it is damaged our impulses will no longer be controlled and we are more likely to act upon them, including aggressive impulses. Damage in the ventromedial pre-frontal cortex (vmPFC) has been linked with aggression.
The prefrontal cortex inhibits the amygdala, so when it is damaged the amygdala is no longer inhibited leading to an increase in aggression.
A reduction in volume of gray matter in the pre-frontal cortex has been found in people with antisocial personality disorder.
Lower serotonin in the pre-frontal cortex has been linked to higher levels of aggression.
There have been several studies to support this explanation of aggression giving it credibility. Flynn (2006) found that when the hypothalamus in cats was stimulated this lead to predatory aggression.
Kluver and Bucy (1939) were early researchers who, using Rhesus monkeys, removed the main areas of the limbic system including the amygdala, hippocampus and surrounding cortical areas. They found that the monkeys displayed an absence of emotional, motor and vocal reactions normally associated with stimuli or situations eliciting fear and anger. Lesioned monkeys also lost the social understanding of group hierarchies and would try to fight the more dominant and larger members of the group. This research demonstrates the importance of the limbic system in regulating aggressive responses. One of the main criticisms of research using animals to provide evidence for aggression in humans is the differences between animal and human physiology and the question of whether we can extrapolate research findings from animals to human aggressive behaviour. Despite humans and monkeys both possessing similar neural structures, we cannot be sure that the processes involved in mediating aggression in humans are the same as those shown in animals such as the Rhesus monkey.
More recent technological advances have allowed neuroimaging techniques such as MRI scans to investigate the relationship between neural structures such as the amygdala and aggressive behaviour. Wong et al. (1997) undertook MRI scans of 19 violent male criminals in Broadmoor hospital and compared the size of the amygdala with 20 ‘normal’ control subjects. He found that the volume of the amygdala was significantly smaller in the 19 violent criminals, thus supporting the role of the amygdala and limbic system in aggression. One of the problems with this research is a lack of population validity: the sample was relatively small, and thus the issue of whether these findings can be generalised to the wider population can be raised. The research can be accused of gender bias, as their research was confined to males; therefore, caution must be taken in using this research to explain aggression in females. When research is used to explain behaviour is both males and females yet only undertaken on males, this is called beta bias.
The case of Phineas Gage showed that damage to the brain due to a head injury can lead to an increase in aggression (see video outlining his case study above). The case of Charles Whitman who had a tumour pressing against his amygdala has been linked to his murders. Both of these are only case studies, leading to generalisation issues; their brain damage may not have been limited to one specific brain area.
Identify two areas of the brain that are thought to influence aggression in humans. (2) June 2017
Describe the role of the pre-frontal cortex as an explanation of aggression. (3) January 2020
Anastacia had an accident where she slipped on a wet floor, banged her head and was unconscious for a short time. Since then she has become more aggressive, getting angry quickly and often shouting at her friends if she thinks they are wrong. Anastacia recently hit another person who accidently pushed her in a crowded room. Describe brain functioning as an explanation for Anastacia’s aggression. (4) June 2018
Describe how damage to the limbic system may cause the increase in aggression shown by Petal. (4) October 2019
Explain one strength and one weakness of brain functioning as an explanation of aggression in humans. (4) June 2017
Explain one strength and one weakness of brain functioning as an explanation for Anastacia’s aggression. (4) June 2018
Explain one strength and one weakness of damage to the limbic system as an explanation of Petal’s aggression. (4) October 2019
Discuss how different brain areas and brain functioning could account for Grei’s aggressive behaviour. (8) June 2019
The structure of the brain, different brain areas and brain functioning have been put forward as an explanation of human aggression. To what extent do you agree that this is a complete explanation of human aggression? (12) January 2017