The Vietnam Head Injury Study (VHIS) is a longitudinal that gathers and analyzes data from Vietnam war veterans. It has contributed significantly to our understanding of the brain as it has enabled psychologists to study veterans who have damage to particular areas of the brain and compare them with other veterans who have not suffered any damage. Through making these comparisons and seeing the effects of damage to the brain on behaviour, we can make conclusions and hypotheses about the role and function of particular areas of the brain.
You can read more about the Vietnam Head Injury Study in this interesting article from the New Yorker.
In one report from the VHIS, Grafman et al. (1996) 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. The prefrontal cortex also allows us to think about the long-term consequences of our actions and to run things through in our minds, so this is another way that it might help to control our impulsive reactions – if we can foresee the negative consequences of an action (e.g. being violent towards someone), we might not act that way but restrain ourselves instead.
In this study, family observations and self-report forms (participants filled forms out themselves) 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. (Grafman et al, 1996).
In this study we can see that while the evidence suggests there are biological correlates of violence and aggression (i.e. the healthy functioning of the prefrontal cortex), there is still an environmental factor that is influential.
Grafman, J., K. Schwab, D. Warden, et al. “Frontal Lobe Injuries, Violence, and Aggression: A Report of the Vietnam Head Injury Study.” Neurology 46.5 (1996): 1231.
You can find the original article here.