When it comes to committing violent crime, psychopaths may not be bad to the bone, but a new brain study suggests they may lack key neural structures—literally less gray matter—involved in empathy, moral reasoning, and feelings of guilt.
And that gives grounds for optimism about the potential to rehabilitate nonpsychopathic offenders, according to a British neuroscientist who studies the brains of the violent.
Those neural deficiencies seem to set psychopaths' brains apart from the brains of other violent offenders without psychopathic traits, says Dr. Nigel Blackwood. The King’s College, London researcher led a study on violent offenders published in the Archives of General Psychiatry.
“The headline for me would be that we should be more hopeful about the treatability of [nonpsychopaths] than perhaps we are,” he says. “Lumping them all together with the psychopathic group and being therapeutically pessimistic about them isn’t justified.”
Most violent offenders meet the criteria for so-called “conduct disorder” in childhood, Blackwood says, and as adults they tend to show signs of antisocial personality disorder: emotional instability, impulsivity, high levels of mood and anxiety disorders, and reactive aggression.
But a subset of children with conduct disorder also display distinctive callous and unemotional traits, and often grow up to meet the definition of psychopathy, which typically includes lack of empathy and remorse, aggressiveness, and arrogance.
During the five-year study, Blackwood and his research team recruited 66 men to undergo structural MRI scans to measure the volume of gray matter—neuron cell bodies—in various brain regions. The subjects included 17 men who had served prison time for violent offenses like rape and murder and who met the criteria for psychopathic antisocial personality disorder, 27 violent offenders with antisocial personality disorder but lacking psychopathy, and 22 healthy nonoffenders.
The men with psychopathic traits had significantly less gray matter in two brain areas than the nonpsychopathic offenders and the healthy control group. The gray matter volumes of violent offenders without psychopathic traits were quite similar to those of the nonoffenders, Blackwood says
The affected brain areas—the anterior rostral prefrontal cortex and the temporal poles—play an important role in our ability to infer what other people are feeling and to monitor our own behavior. “These are exactly the areas that underpin things that psychopaths do badly, like processing the fear of others, the empathic understanding of distress, or having self-conscious emotions like embarrassment or guilt,” Blackwell says. “We know these things go wrong in psychopaths, so we can at least suggest there are links.”
The study controlled for a history of substance abuse and mental disorders like schizophrenia that affect brain structure, Blackwood says. Prior brain scan studies, including some conducted by Kent Kiehl at the Mind Research Network in New Mexico, have found gray matter deficiencies in other brain areas, such as the limbic system, Blackwood says, but they have not systematically compared psychopaths with nonpsychopathic offenders and a healthy control group.
Of note: many of the men classified as psychopaths in Blackwood’s study would not have met the criteria for psychopathy in the United States, he says. Psychopathy is diagnosed with a standard checklist that scores various traits on a scale of 40. In Europe, a score of 25 qualifies someone as a psychopath, he says, while the threshold in the U.S. is 30. The average score in the British study was 28, he says.
“I’m always slightly careful about this with American audiences,” Blackwood says in trying to explain the differing thresholds. “It’s something to do with a different approach to the self in America. There is a degree of narcissism that is more culturally appropriate in America than it is in England.”
Meanwhile, research shows that callous and unemotional behavior in children may often be inherited, and there are ongoing efforts in the U.S. and Europe to understand how psychopathy develops—and whether early intervention may ward it off.