A neuroscientist who had his brain scan handy while reviewing those of various psychopaths, schizophrenics, and even some murderers serendipitously diagnosed his own “low activity in areas of the frontal and temporal lobes linked to empathy, morality and self-control.” See image above. According to Joseph Stromberg's blog post at Smithsonian Magazine:
... when he underwent a series of genetic tests, he got more bad news. “I had all these high-risk alleles for aggression, violence and low empathy,” he says, such as a variant of the MAO-A gene that has been linked with aggressive behavior. Eventually, based on further neurological and behavioral research into psychopathy, he decided he was indeed a psychopath—just a relatively good kind, what he and others call a “pro-social psychopath,” someone who has difficulty feeling true empathy for others but still keeps his behavior roughly within socially-acceptable bounds.
It wasn’t entirely a shock to [James] Fallon, as he’d always been aware that he was someone especially motivated by power and manipulating others, he says. Additionally, his family line included seven alleged murderers, including Lizzie Borden, infamously accused of killing her father and stepmother in 1892.