What Psychopaths Tend To Have In Common

By the time most psychopaths burst into the media spotlight, they're already fully-formed adults. But what makes someone a psychopath? The answer is just as complicated as it seems. For one thing, it's not like a switch is flipped and suddenly, someone finds themselves getting acquainted with their inner Hannibal Lecter; while there's a substantial genetic component, there's some environmental influence too. (More on that later.) Furthermore, some psychologists believe that the disorder is less binary than previously believed. Despite their portrayal in popular culture, psychopaths aren't necessarily violent.

Just ask Jim Fallon — the scientist, not the late-night TV host. A professor at the University of California, Irvine, he's been studying neuroscience for more than 35 years, and in 2005, he turned his attention to psychopathy, comparing brain scans of people with and without psychopathic tendencies. Fortunately for anyone with an interest in the subject (read: everyone), Fallon gave a TED Talk on the information he gathered, and it's just as fascinating as you'd expect. The talk is from 2009, but I'd argue that it's still relevant today; besides, with Halloween looming at the end of the month, it seems like an appropriate time to unearth Fallon's work. So buckle up, gird your loins, or do whatever else you need to do in preparation, because we're about to take a look at what makes psychopaths tick.

As Fallon explains in his talk, he compared PET scans of the brains of about 70 different people. Some were healthy, while others belonged to convicted murderers — but he wasn't told which was which. During his analysis, he found certain characteristics present in the killers across the board. One of the most notable findings was a difference in brain functioning, particularly in parts of the brain associated with emotion and empathy. "The pattern is that those people, every one of them I looked at, who was a murderer, and was a serial killer, had damage to their orbital cortex... and also the interior part of the temporal lobe," Fallon says in the TED Talk.

Genetics also came into play: Fallon goes on to note the existence of a "major violence gene" called MAO-A, which regulates the neurotransmitter serotonin during fetal development. In the past, the gene has been associated with antisocial behavior, which, according to Fallon, could be because it desensitizes babies to serotonin by providing too much of the neurotransmitter in the womb. (Seratonin has been implcated in the perception of morality.) Additionally, MAO-A could explain why the vast majority of psychopaths are men; it's a sex-linked gene, which means that it's passed through the X chromosome. Women have two of those, so their psychopathic tendencies might be "diluted out" by the other parent's chromosome, but men only have one. If their mothers pass down MAO-A, they're stuck with its influence.

This is all stuff that predisposes people to become psychopaths, but there's a final piece to the puzzle: Environment. In his talk, Fallon explains that if someone already has these characteristics — the genetic background and brain development — a traumatic event may be the final straw. "If you have that gene, and you see a lot of violence in a certain situation, this is the recipe for disaster, absolute disaster," he says. It's telling that many famous psychopathic killers, like John Wayne Gacy and Jeffrey Dahmer, had abusive childhoods.

But there's good news! Having these tendencies doesn't automatically make anyone a killer. Jim Fallon himself has a rather checkered family history, but I'll let him explain it to you. Check out his TED Talk below.

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