While neither term appears in the Diagnostic and Statistical Manual of Mental Disorders, the medical handbook used by psychiatrists, psychopaths can be divided into two categories, according to James Fallon, a neuroscientist at the University of California at Irvine School of Medicine who specializes in studying psychopaths.

The first category includes what are known as primary psychopaths. The second includes what are known as secondary psychopaths, or sociopaths, reports The Business Insider.

Here's what sets the two apart:

(Note: These definitions are meant to be informative only, not to be used as a diagnostic tool.)