Psychopaths can be cured of their disorder through "brain training" as they do not lack empathy - just the ability to use it.
Previous studies had suggested that the brains of psychopaths were different to other people in that the part that processes emotions and self-awareness was diminished or missing altogether.
Fresh research has concluded that the problem is not a lack of empathy but the fact that it is not automatic, suggesting that the personality disorder could be cured through rehabilitation.
People diagnosed with psychopathy often pose a significant threat to society because they are more likely to harm others. Recent research showed they have reduced empathy while witnessing others being harmed.
But researchers at the University of Groningen found that when asked to imagine what a person in pain was feeling, psychopaths could activate empathy.
Harma Merffert, first author of the paper, said: "All participants first watched short movie clips of two people interacting with each other, zoomed in on their hands. The movie clips showed one hand touching the other in a loving, a painful, a socially rejecting or a neutral way. At this stage, we asked them to look at these movies just as they would watch one of their favourite films."
The researchers then asked the 18 psychopath participants to empathise with one of the actors in the films.
"In the third and final part, we performed similar hand interactions with the participants themselves, while they were lying in the scanner, having their brain activity measured," Meffert said.
"We wanted to know to what extent they would activate the same brain regions while they were watching the hand interactions in the movies as they would when they were experiencing these same hand interactions themselves."
In the first part of the test, when they were passive observers, regions of the brain involved in their own actions, emotions and sensations were less active than shown in a normal person.
However, in the second part, they were able to activate emotional responses.
"When explicitly asked to empathise, the differences between how strongly the individuals with and without psychopathy activate their own actions, sensations and emotions almost entirely disappeared in their empathic brain," second author Valeria Gazzola said.
"Psychopathy may not be so much the incapacity to empathise, but a reduced propensity to empathise paired with a preserved capacity to empathise when required to do so."
Researchers believe their reduced spontaneous empathy coupled with the preserved capacity for empathy may be the reason why psychopaths have the ability to harm while being able to be charming.