Structural (left) and functional (right) MRI scan data shows that subjects with the violence-related version of the MAO-A gene (MAOA-L) had reduced volume and activity of the anterior cingulate cortex (blue area in front part of brain at left and corresponding yellow area in at right), which is thought to be the hub of a circuit responsible for regulating impulsive aggression. The color-coded areas show where subjects with the L gene type differed from subjects with the H gene type. Source: NIMH Clinical Brain Disorders Branch

A few months ago I wrote a two-part post about how fMRI and PET scan technology were able to detect differences in the brains of psychopaths compared to non-psychopathic individuals. This area of research has identified that psychopathy has a genetic component, and has even been used in court cases to determine sentencing.

Recently, I came across a story on NPR about a neuroscientist who studies these scans, and decided to analyze his own brain scans and those of his family to determine if psychopathy was present. What he found was more than a little disturbing to him…

James Fallon reported that there was a documented history of criminal activity on his paternal side of the family, (including a relation to Lizzy Borden), that made him curious to view the brain scans of his family. They had all previously submitted brain scans and a blood sample in order to rule out a risk for Alzheimer’s, so he had the materials already.

“Fallon examined the images and compared them with the brains of psychopaths. His wife’s scan was normal. His mother: normal. His siblings: normal. His children: normal…however, his orbital cortex looks inactive. ‘If you look at the PET scan, I look just like one of those killers,’ said Fallon.”

Fallon decided to go one step further and analyze the blood samples in search of genes that are associated with violence; namely the MAO-A gene (monoamine oxidase A), specifically MAOA-L (low activity variant). This gene has been controversially dubbed the “warrior gene” due to its association with violent behavior (more on that discussion in another post). Much to his dismay, Fallon again found that everyone in his family has the low-aggression variant of the MAO-A gene, except for one person—himself.

“I’m 100 percent. I have the pattern, the risky pattern,” he says, then pauses. “In a sense, I’m a born killer.”

Fallon isn’t, of course, a killer; however, genetically speaking he meets the criteria of psychopathy.

Fallon reported that, “he had a had a terrific childhood; he was doted on by his parents and had loving relationships with his brothers and sisters and entire extended family.”

And therein lays the process of how one person can become a psychopath, and another to go on with a fairly “normal” life. Without the environmental component of an abusive or neglectful childhood, the genetic factors are not “activated.” This provides further insight into psychopathy—it is not only important to study those who are psychopaths, but also those who had major predispositions to become psychopaths, but did not. The protective factors can help us to better understand and encourage preventative measures.

Had Fallon had a different kind of childhood his life may have taken an all together different path…or not.

It’s difficult to know what particular factors protected Fallon from becoming a psychopath, but this certainly further supports the notion that our genetics do not predetermine our life’s course.



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    Last reviewed: 4 Sep 2010

APA Reference
McAleer, K. (2010). The Effect of Nature & Nurture on Psychopathy: The Case of James Fallon. Psych Central. Retrieved on March 29, 2015, from



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