What goes on inside the brain of a psychopath? One new study, the latest in a line of controversial recent research tackling that question, offers yet another clue about how the grey matter of individuals diagnosed with psychopathy — a complex personality disorder often characterized by impulsive behavior, lack of remorse, and antisocial tendencies — might be “hardwired” differently than those who don’t fit the profile.

A research team based out of the University of Chicago used functional magnetic resonance imagery (fMRI) — tests that evaluate brain activity — to scan the grey matter of 80 male prisoners aged 18 to 50 during a series of experiments. Some of these prisoners met the standard diagnostic criteria for psychopathy, known as the Hare Psychopathy Checklist, while others acted as controls.

"Psychopaths are emotionally ‘aware’ of the pain of others, but this signal doesn’t register."

Researchers wanted to figure out how the brains of psychopaths and non-psychopaths responded to two violent visual stimuli: videos of people being intentionally harmed, and photos of people experiencing pain and suffering. Indeed, differences arose between the two groups. When viewing the videos and images, study participants with diagnosed psychopathy exhibited less activation in several brain regions, including the orbitofrontal cortex and ventromedial prefrontal cortex — both key to evaluating consequences and weighing decisions. They also exhibited greater activation in the insula, which plays “a pivotal role in emotional awareness,” study author Jean Decety, Ph.D., told The Verge. Combined, the results suggest that “psychopaths are emotionally ‘aware’ of the pain of others, but this signal doesn’t register in other regions of the brain ... and this contributes to their insensitivity and lack of empathy,” Decety noted.

The idea that psychopaths lack empathy is hardly surprising. But this latest research, the first fMRI study to target brain activity in the context of empathic responses, joins a growing body of evidence which indicates that psychopathic behavior might be reflected in distinct, perceptible differences inside the brain. Several earlier studies, many of them by Dr. Kent Kiehl, a professor of psychology at the University of New Mexico and a co-author on this research, suggest that psychopathic brains exhibit unique differences in structure and function.

"Psychopaths do tend to process this information differently."

In one particularly fascinating instance, Kiehl in 2009 performed a series of tests on Brian Dugan, a convicted rapist and serial killer. Dugan’s brain exhibited similar characteristics to those of these new study participants and around 1,100 others that Kiehl had already evaluated at the time. “We have a lot of data that shows psychopaths do tend to process this information differently,” Kiehl told NPR. “And Brian looked like he was processing it like other individuals we’ve studied with psychopathy.” The finding was used, unsuccessfully, by Dugan’s defense team in an effort to prevent their client from being sentenced to the death penalty — the first time fMRI data was admitted as evidence in capital sentencing.

Fascinating as this burgeoning field of research might be, it isn’t without controversy. Most notably, some experts argue, fMRI techniques aren’t refined enough to pick up on subtleties that might be integral in drawing any conclusions about psychopathy. “If you get more and more refined, an area that once looked highly active starts to look more like a mosaic of activity,” Dr. James Fallon, a professor of psychiatry and human behavior at UC Irvine, told The Verge. “And maybe one part of that mosaic processes a certain kind of empathy, and another part processes another kind. We just don’t know.”

“At what point can you conclusively say, ‘this is a certain kind of person’?"

Not to mention that the brain is only one part of a complex equation — one that’s also informed by genetics and an individual’s environment. “At what point can you conclusively say, ‘This is a certain kind of person’?,” Fallon asked. “Once you look at subjects, you define them genetically, you define them with brain imaging, you look at their behavior, and you look at their environment ... then you get a little closer.”

But the role of fMRI scans in evaluating psychopathy is becoming increasingly salient, several experts told The Verge, as the overlap between neuroscience and the legal process continues to evolve. Anecdotal evidence suggests “an increased use of neuro-imaging in capital sentencing cases,” Stephen J. Morse, J.D., Ph.D., a professor of law and psychiatry at the University of Pennsylvania, said. And preliminary studies indicate that judges might dole out more lenient sentences when biological explanations of a defendant’s psychopathy are introduced.

“Some individuals are very excited about the potential of neuroimaging to change our practice, policy, and individual case decision-making,” Morse said. “[But] I don’t think we have the data, yet, to alter our moral and legal landscape.”