A new study finds psychopaths do not lack empathy. They just possess the ability to turn it on and off—perhaps making some curable.

Critics say psychopaths only lack a certain form of empathy. Their ability to understand it is part of what makes them so dangerous.

“The findings are fascinating,” says Martha Stout, author of The Sociopath Next Door. The UK and Germany apparently agree, recently making a book by the new study's author a Der Spiegel  bestseller.

Psychopaths can be alternately charming and brutal. There is something real in both their “faces.”

For the new Brain study, psychopathic criminals, lying in MRI’s, watched videos of a person being hurt by someone else. Only when asked to imagine the receiver’s pain did appropriate areas in psychopaths’ brains—involving pain response—ignite in a way mirroring controls’.

Professor Christian Keysers performing an fMRI scan. (Source: Royal Netherlands Academy of Arts and Sciences)Without instruction, psychopaths displayed reduced activity in brain regions associated with both pain and pleasure. “The vicarious activation of motor, somatosensory, and emotional brain regions was much lower in the patients with psychopathy... The (standard) theory seemed right: their empathy was reduced, and this could explain why they committed such terrible crimes without feeling guilt,” wrote Groningen University neuroscientist Christian Keysers in a Psychology Today article about his new Brain study. (Keysers' new book is The Empathic Brain.)

But when the team showed movies after mandating empathy, “this simple instruction sufficed to boost the empathic activation in their brain to a level that was hard to distinguish from that of the healthy controls. Suddenly, the psychopaths seemed as empathic as the next guy. Their empathy was switched on.”

The finding may bring hope, Keysers added by email. "There is a fundamental difference between the capacity for empathy, which psychopaths have, and the propensity to always be empathic by default. If we can turn capacity into propensity, we could really help them."

Some supporters note many therapists try this with psychopathic children. They tell kids how “mirror neurons” light up in the same brain areas of people watching others—and those being watched. (Keysers’ team pioneered mirror neuron research.) Such therapists tell patients that brain synchrony indicates they can empathize.

Others are less sure.

“It's very important people not misunderstand,” says Stout. “Sadly, I don't think the results speak to a cure. “

Studies of “disorders of consciencelessness," she says, show that “psychopaths/sociopaths are often exceedingly charming, can ‘read’ people when it suits their purposes, and can learn (with calculated effort) to recognize and imitate overt signs of emotion in others. I find it interesting but not surprising that functional mirror neurons are present. Psychopaths can read other people if they choose.”

This image shows the movies shown to the participants (left) and brain activation of the participants with psychopathy without instructions (behind) and with instructions to empathize (front). (Source: Royal Netherlands Academy of Arts and Sciences)

But, says Stout, “They just don't usually choose to, because the tragic deficit appears to be the maldevelopment of the paralimbic system (the brain’s emotional area). This more general deficit prevents psychopaths from forming bonds to others, prevents them from loving or caring. Where emotion is concerned, psychopaths can see it in others when they make a concerted conscious effort. They just don't care to do so unless they can use it to their own advantage.”

This study may illustrate psychopathy’s danger, not its curability. “Eerily, in a sense, mirror neurons just make psychopaths more effective psychopaths when there's a pay-off. Conscience is a sense of obligation based in the ability to form emotional attachments to others. It is this ability, not the ability to read or reflect, tragically missing in psychopathy/sociopathy.”

Says Columbia University forensic psychiatrist Michael Stone:  “One problem: the word "empathy" is used in different ways in the UK/Canada and the US.  There, they conflate "empathy" (the ability to cognitively grasp another’s emotional state) with "compassion" (the propensity to sympathize with another's distress). In the US, we use "empathy" only in the latter sense.” The Brain study defines empathy “the combined way.”

Stone continues: “Many psychopaths, even serial killers, know if a kid's crying, he's distressed, probably got separated from his mom. But the compassionate person feels sad for the kid, and takes measures to reunite the two. The psychopath uses the opportunity to take the kid by the hand, and pretends to get him hooked up with his mom -- but leads him instead to his car and kidnaps him. Zero compassion….Do I think psychopaths [at the edge of psychiatric scales] can develop genuine compassion? The likelihood is very, very low.”

Regardless, says Stout: “I hope these findings will increase our understanding.”