Most of us find it impossible to understand how people can commit violent crimes against their fellow humans. Yet, these same crimes hold a strange fascination as evidenced by the numerous non-fiction books on serial killers and related topics. As Dorothy Lewis, a psychiatrist and one of the pioneers of the study of violent inmates, put it: “It´s the act of murder that fascinates us and tickles our limbic systems.”
But we should, of course, not just publish and read best-sellers but also study violence scientifically. Such studies can have very important clinical, societal and legal implications.
A little history: Phineas Gage
Phineas Gage is probably the most famous victim of traumatic brain injury. In 1848 an accidental explosion caused a tamping iron to penetrate Gage´s skull and pass through his left frontal lobe. He lived on for 11 ½ years but was a changed man. Twenty years after the accident Gage´s physician, John M. Harlow, wrote: “The equilibrium or balance, so to speak, between his intellectual faculties and his animal propensities, seems to have been destroyed.” Later interpretations of Gage´s symptoms have sometimes been imprecise but his story has been well documented by Malcolm Macmillan in an excellent book, An Odd Kind of Fame: Stories of Phineas Gage.
Some modern writers have discussed Gage in the context of psychopathy but this is probably reaching too far. However, recent research has demonstrated a relationship between violent behavior and abnormal functioning and structure of the frontal lobes and related areas. In fact, individuals with injuries affecting the orbitofrontal cortex have been called pseudopsychopathic but psychopathy is closely related to criminality.
Our brain´s CEO
The role of the frontal lobes remained somewhat of a mystery long after Gage´s ordeal. We know now that injuries to the frontal lobes or to frontal lobe circuitry can result in profound changes in behavior. Furthermore, as the frontal lobes have a complex relationship with the rest of the brain they are quite vulnerable. Very many diseases and conditions affect the frontal lobes and are characterized by what we call executive problems, that is problems with control of behavior and emotions, insight and empathy. In short, all those aspects of behavior that make us socially and emotionally well-adapted individuals, able to have meaningful and caring relationships without transgressing social norms.
Serial killers: is it all in the brain?
In the past decade the use of brain imaging techniques has become increasingly popular in studies of psychopathy. However, published studies are still relatively few and differences in methodology between the studies make interpretation of the data difficult. For example, the definition of psychopathy is not uniform and the possible sub-types of psychopathy are generally not taken into account. Still, the evidence for structural abnormalities in the brains of psychopaths is mounting. Studies have linked psychopathy with various abnormalities in brain areas related to social cognition, emotion, empathy as well as memory and learning. The brain areas most commonly involved are regions within the frontal lobes and the temporal lobes, both grey matter and white-matter pathways. No single specific brain region is consistently related to psychopathy. It is more reasonable to expect a network of several areas, or a circuitry, to be involved.
In a brand new, well conducted, study, Sarah Gregory and her co-workers found that violent psychopathic offenders had less grey matter than violent offenders without psychopathy. The differences were on both sides of the brain, in the medial area of the prefrontal lobe as well as in the most anterior part of the temporal lobes. The groups were matched on age, IQ, history of substance abuse, and did not have histories of brain injury or other neurological problems which could have explained their reduced volume in the grey matter in the brain.
A word of caution
Although a relationship has been found between abnormalities in the brain and psychopathy it does not mean that everyone who has a similar abnormality in the brain will become a serial killer or commit hideous crimes. The relationship between brain and behavior is much more complex than that. There are multiple interacting causal factors that contribute to violent behavior (e.g. psychosocial variables, past physical and sexual abuse, drugs/alcohol). Frontal lobe, or other brain impairment, is only one possible contributing factor.
Listen to the following story on National Public Radio. You will hear a very personal account from neuroscientist James Fallon
Illustration: By Polygon data were generated by Life Science Databases(LSDB). (Polygon data are from BodyParts3D.) [CC-BY-SA-2.1-jp (http://creativecommons.org/licenses/by-sa/2.1/jp/deed.en)], via Wikimedia Commons
Gregory, S. et al. (2012). The antisocial brain: Psychopathy matters. Archives of General Psychiatry. Published online May 07, 2012. doi:10.1001/archgenpsychiatry.2012.222.
Koenigs, M., Baskin-Sommers, A. & Newman, J. P. (2011). Investigatin the neural correlates of psychopathy: a critical review. Molecular Psychiatry, 16, 792-799.
Lewis, D. O., Pincus, J. H., Feldman, M. et al. (1986). Psychiatric, neurological, and psychoeducational characteristics of 15 death row inmates in the United States. American Journal of Psychiatry, 143, 838-845.
Lewis, D. (1998). Guilty by reason of insanity. New York: Random House.
Macmillan, M. (2000). An odd kind of fame: Stories of Phineas Gage. Cambridge MA: MIT Press. (for a brief account see “Phineas Gage: A Case for All Reasons” (In C. Code, C.-W. Wallesch, A.-R. Lecours, and Y. Joanette, eds., Classic Cases in Neuropsychology (pp. 243-262), 1996, London: Erlbaum)
Macmillan, M. (2008). Phineas Gage – unravelling the myth. The Psychologist, 21 (9), 828-831.