Killers Are Born — and Made

By Temma Ehrenfeld  @temmaehrenfeld
March 20, 2015
California, USA --- Bengal Tiger Walking in Snow --- Image by © DLILLC/Corbis

A loving household in childhood may keep them from violence.

While studying what makes the brains of killers stand out, neuroscientist James Fallon was sifting through thousands of brain scans taken from all kinds of people — not just murderers. To keep the research objective, the scans were coded, so that Fallon didn’t see names. Scans of the brains of people in his family also lay on his desk. These had been assembled for a project studying Alzheimer’s. At the bottom of the family pile, he found a scan that looked like it belonged to a psychopath: it showed low activity in areas tied to self-control, empathy, and ethics. Because he knew it came from a member of his family, he looked up the name. The pathological brain turned out to be his own, he recalls in his book, “The Psychopath Inside.”

At first he thought this must be a mistake. But Fallon underwent a series of genetic tests and discovered a number of variants associated with violence and low empathy. As the news settled on him, it made sense: he counts seven alleged murderers on his family tree. Although he hasn’t confessed any crimes, he now admits that he’s “aggressive” and “obnoxiously competitive.” 

Stories like Fallon’s suggest that killers are both born and made. One of the variants that put Fallon at higher risk of becoming a killer also can lead people to be more substantially affected by their upbringing. He believes that he turned into a “pro-social psychopath” — someone who behaves within social norms but isn’t empathic — because his parents were devoted to him. Had he been abused or neglected as a child, it seems possible that this aggressive competitive scientist would instead have become a killer.    

In “The Anatomy of Violence,” University of Pennsylvania criminologist Adrian Raine lines up several biological markers for potential criminality: being male, certain gene variants, a low resting heart rate, brain damage, and a mother who smoked and drank while carrying you in her womb. Raine’s research backs up Fallon’s observation about devoted parenting: when children are separated from parents before the age of three, or their mothers are cold and their fathers disengaged, they are more likely to show signs of a psychopathic personality at the age of 28.

The signs of a criminal future show up before the teens, he argues. In another study, he and his team had about 200 11-year-olds from two towns on the tropical island Mauritius take a test measuring their impulsivity — they saw the numbers 1-9 on a screen and had to press a button when they saw 5. The game produced a measure of their “P3 amplitudes” (the larger the P3, the greater the control they had in their nervous system). Their parents also filled out questionnaires about their behavior. As predicted, children with low P3 amplitudes also were more likely to act up — swearing, getting into fights, making threats. When the children had grown to age 23, the researchers checked who had been convicted of a crime. As expected, significantly more of the low P3 kids were offenders.

In his book, Raine reports that he had a difficult birth and suffered from a vitamin deficiency as a child, two circumstances that can lead to poor self-control. As a young man, he had a low resting heart rate. Worst of all, his brain scans look like those of serial killers.

It’s good to know that people carrying the seeds of criminality may choose to study it instead. But you might think twice before you date a criminologist. 


April 02, 2020

Reviewed By:  

Christopher Nystuen, MD, MBA