A scientist who studies psychopaths found out he was one by accident - and it completely changed his life

James Fallon is an expert on the minds of psychopaths.

A neuroscientist at the UC Irvine School of Medicine, Fallon (not to be confused with Jimmy Fallon, the popular TV host) first began studying the brains of murderers, rapists, and other criminals in the mid-1990s, when his university got its first PET brain-imaging machine. But he didn't start focusing on this area of research until about 10 years ago, when something happened that made him re-think his entire career focus.

Around 2005, Fallon started to notice a pattern in the scans of some of the criminals who were thought to be psychopaths, which led him to develop a theory: All of them appeared to have low levels of activity in a region of the brain located towards its center at the base of the frontal and temporal lobes. Scientists believe this region, called the orbital cortex, is involved in regulating our emotions and impulses and also plays a role in morality and aggression.

One day, Fallon's technician brought him a stack of brain scans from an unrelated Alzheimer's study. As he was going through the scans of healthy participants, they all looked normal - no surprises. But then he got to the last one.

It looked just like those of the murderers.

The identity of the brains in the scans had deliberately been masked so as not to bias the results. But Fallon couldn't leave it alone. "I said, we've got to check the [source] of that scan," Fallon recalled recently to Business Insider. "It's probably a psychopath... someone who could be a danger to society."

Turns out, the image wasn't a scan of just any random participant - it was a scan of his own brain.

The makings of a psychopath?

Psychopathy is not recognized as an official disorder, but the Diagnostic and Statistical Manual of Mental Disorders (DSM) lumps psychopaths or sociopaths under the term antisocial personality disorder. People with this disorder, it says, exhibit impairments in personality functioning and pathological personality traits. For example, they may be egocentric, manipulative and show a lack of empathy.

In the 1970s, Canadian psychologist Robert Hare developed a 20-question psychopathy checklist as a way to assess whether or not someone is a psychopath based on the presence of specific personality traits and behaviors. A revised version of the test is still widely used, though several analyses of studies suggest it performs no better than chance at predicting violent behavior.

When Fallon saw that his own scan fit the pattern of brain activity he had found in the psychopaths, he started to question his theory. He thought to himself, "I'm okay, I'm not a bad guy."

But when he went home and told his wife what had happened - how his brain resembled that of a psychopath, at least according to his theory - she reacted very strangely.

It wasn't that surprising, she said.

But it wasn't just his wife who reacted this way. Friends and colleagues told him the same thing, that he was "kind of not there emotionally," Fallon recalls. Even his daughter thought so - as a young child, she painted her dad as a "dark figure." Fallon's psychiatrist friends described things he had done in the past that they said showed a profound lack of empathy (one of the telltale signs of psychopathic tendencies), like skipping a friend's funeral because he thought it might be boring. His friends and family agreed. "I realized people had been telling me something for years, I just didn't put it together," Fallon said.

It's important to keep in mind that scientists are still researching psychopathology and they don't have all the answers yet. But they think that people like Fallon have a connection with the world that's very different from others.

According to some of this research, psychopaths understand when there are people in need or in pain, but they don't feel it viscerally the way most people do. As Fallon put it, "I don't get the interpersonal warm and fuzzies."

So Fallon started looking to his genetics for answers. It turns out he has a gene that's been linked, in several studies, with an increased risk of violent and aggressive behavior.

The gene is called MAO-A (monoamine oxidase A), and it's pretty controversial - for obvious reasons. Known as a "warrior gene," it's responsible for making a protein that breaks down certain types of chemical messengers. These messengers control our thinking and behavior, and the ones that the warrior gene affects include dopamine, noradrenalin and serotonin, which are all linked to our mood.

Nature vs. nurture

Having the gene isn't the be-all-and-end-all determinant of personality, of course: A whole host of factors, including our environment, affect how we turn out as well.

Fallon estimates that for most people, early-life environment has only a partial effect on our development. But a minority of people (he estimates about a quarter of us) are genetically wired to be very sensitive to their early environment. For these people, "if [the brain] sees a hostile world, the only way to survive is to be hostile. If it sees a normal world, it will be normal," he said.

And there's research to back this up: A 2002 study that followed a large group of male children who were maltreated (physically or sexually abused, for example) from birth to adulthood found that the ones who had a particular version of the MAO-A gene grew up to develop antisocial behavior, whereas those with a different version of the gene did not.

Fallon suspects that someone with this gene who's abused as a child, for example, could be pushed to act on his or her violent or uncaring instincts, says Fallon. By contrast, someone with the same gene who's treated well as a kid could potentially avoid going down that path, he says.

Still, research suggests we should be cautious about linking the MAO-A gene with violent behavior. While studies reveal that there is a connection between genes and violence, they don't show definitively that having these genes is what makes people violent.

At around the same time that Fallon was discovering these dark sides of himself, he learned that his great-grandfather, Thomas Cornell, had allegedly murdered his mother in 1673. That side of the family also produced half a dozen other alleged murderers, including the infamous Lizzie Borden, a young woman who was tried (and controversially, acquitted) for the brutal axe murders of her father and stepmother in 1892.

While none of this proves that Fallon is a psychopath, "it was like somebody was trying to give me a message," Fallon said.

A personal trial

For his own part, once Fallon realized he shared some of the genes, brain activity, and behaviors observed in other psychopaths, he decided to do some experimenting in his own life - he began acting really nice and being more conscientious, even though he didn't really want to.

For example, he started doing little things like opening doors for people, and attending events like weddings and funerals, which he had never bothered to do before. His wife noticed his behavior and said she liked it, even though she knew it wasn't sincere.

"Maybe if I just acted the part, even if I don't feel it at an emotional level ... [it] would be a good place to start, just to be a good companion and a good friend," Fallon said recently on the storytelling show the Moth. "And so, that's where I am now."

Fallon found that one side effect of acting nice is that it slowed down his ability to think and talk quickly, because he's constantly asking himself what a good guy would do. He also finds life much more tiring, he said.

Still, the fact Fallon's even making these efforts in spite of himself suggests that maybe he's a better person than he gives himself credit for.