Brain Function: The Frontal Lobe and the Prefrontal Cortex
Numerous studies have shown that there are correlations found between brain function and violent behaviour. In order to fully understand these studies, it’s important to have a general understanding of some of the functions of these parts of the brain. The brain is labelled as having different “lobes”.
The frontal lobe is one of the “newer” parts of the brain, evolutionarily speaking. One important function of the frontal lobe is to regulate our impulsive decision making. It also lets us make long-term decision making in the sense that it allows us to foresee and imagine possible implications for our actions. It kind of acts like a “break” on our impulsive behaviour. So when you get really angry at your teacher and you want to curse but don’t because you know that it will get you in trouble, you have your frontal lobe to thank.
The impulsivity of young children can be explained through their still-developing frontal lobes. When learning about the brain, it’s always important to remember that brain function is complex and to avoid the allure of simplifying down to claims like “our frontal lobes control our behaviour.” Human behaviour is far too complex, as is the brain, for both to be boiled down to such a simple statement. A more accurate statement would be “our frontal lobes are associated with self-control.”
The prefrontal cortex is the area at the very front of the brain. The cortex refers to the dense outer layer of the brain where 90% of the brain’s neurons are.
One of the first and most famous studies of a man who had severe damage to his frontal lobe was that of Phineas Gage. Gage was a railroad worker who was putting dynamite into rocks while working with a team to lay tracks. As he used a six-foot bar to pound the dynamite powder into the rocks it ignited, essentially making the long steel pole a bullet that fired up through his left eye, through his skull and landed about 50ft away. Gage survived and was even conscious while he rode on the ox cart to the nearest town. As a result of the incident, Gage’s behaviour seemed to change as he went from being a rather mild-mannered man to “no longer Gage” as his friends said. This was in 1948 and Harow, the Doctor who treated Gage, made a few observations about the change in Gage’s behaviour that has made him one of the first and most famous cases that links brain damage to personality change.
Since Phineas Gage there have been heaps of studies into the correlations between brain damage, brain function and behaviour. With modern imaging technology (MRI’s, fMRI’s, PETs, etc.) researchers can investigate further connections between brain function and behaviour.
The biological correlates of criminal behaviour has been the subject of numerous studies. Time and again research has shown that there are common brain functioning and activity differences in criminals when compared with healthy and normal controls.
When researching these correlates it’s important to remember their general function, but not to oversimplify the biological processes underpinning human behaviour.
Studies have shown that there is a correlation between low functioning frontal lobes and violent behaviour. One study compared 279 Vietnam war veterans who had suffered head injuries that resulted in damage to areas of the brain with 57 healthy controls. The researchers hypothesized that the prefrontal cortex helps exert control over primitive reactions to environmental provocation. In other words, when something makes us emotional neurons in our prefrontal cortex fire (i.e. this part of the brain is active) and this helps to stop us from reacting in a violent or aggressive manner. Family observations and self-report forms were used to gather data on violent and aggressive tendencies in the participants. The researchers gathered data on a range of aggressive and violent attitudes and behaviours. The results showed that those veterans who had damage to their prefrontal cortex had higher levels of violence and aggression than the controls or veterans with damage to other parts of the brain. Verbal violence and aggression, as opposed to physical, was more commonly reported. The study found no correlation between the extent of the brain damage and behaviour, but instead found that “disruption to family activities” was more likely to cause aggressive and violent behaviours. (Graftman et al, 1996). In this study we can see that while the evidence suggests there are biological correlates of violence and aggression, there is still an environmental factor that is influential.
Travis Dixon is an IB Psychology teacher, author, workshop leader, examiner and IA moderator.