In conjunction with the horrific stories in the news as of late, HLN’s Dr. Drew welcomed Dr. James Fallon, a neuroscientist at the University of California, Irvine, who studies the brains of psychopaths.  

Dr. Fallon began by describing some of the features of a psychopathic killer, noting both the “positive and negative” symptoms.

“The positive ones are those that make the psychopaths very sociable,” he said. “They are charming, extremely sociable -- the life of the party. They can be disarming in that way. They’re very friendly, but also, they lack a certain kind of empathy. They may be empathetic in a very different way … lack of empathy and connectedness with people.”

He continued, “Then there's these negative [symptoms], which involves a hyper-sexuality, being really loose morally, but also some criminality, and not taking responsibility for your actions. All of those things make somebody, in a way, parasitic.”

Watch the full and fascinating interview in the video player above.

Dr. Drew airs Monday through Thursday at 9 p.m. ET on HLN. Follow the show on Facebook and Twitter @DrDrewHLN.