Among other traits, psychopaths feel a lack of empathy when other people are in pain, and brain scans now reveal why that is.
Psychopathy is a personality disorder marked by callousness, manipulation, sensation seeking and antisocial behaviours. About 23% of people in prison are psychopaths, compared with about 1% of people in the general population.
In this study, researchers used functional MRI to observe brain activity in 121 inmates at a medium-security prison in the United States who were divided into three groups based on the levels of their psychopathy: high, moderate or low.
The participants were shown pictures of physical pain, such as a finger caught in a door or a toe trapped under a heavy object. They were first asked to imagine that these accidents happened to themselves and then to imagine that they happened to others.
When highly psychopathic inmates imagined themselves in these painful situations, they showed higher-than-normal activity in certain brain regions involved in empathy for pain. But these regions failed to become active when they imagined others in pain.
Moreover, when imagining other people in pain, highly psychopathic inmates showed increased activity in a brain area known to be involved in pleasure, according to the study, which was published on 24 September in the journal Frontiers in Human Neuroscience.
The findings may help lead to new treatment approaches for psychopaths, the researchers said in a journal news release.
Mental Health America has more about personality disorders.