The terms psychopath and sociopath are often used interchangeably, but they aren't quite the same thing.

So what's the difference, you ask?

To find out, we asked James Fallon, a neuroscientist at the University of California at Irvine School of Medicine who specializes in studying psychopaths (and also happens to be one himself).

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

Here's what sets the two apart:

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

But that's not all. According to Fallon, both psychopaths and sociopaths can be further broken down into two subtypes, based on their demeanor: