Hey, let’s face it: Every relationship has its moments. After some arguments, both parties get to walk away feeling like they maybe weren’t at their best. Took things a little too far? A little over the top? A lot over the top? Seems like somebody’s crazy here. Still there’s a big difference between “crazy” with a small “c” and CRAZY, with a capital “K.” Which crazy is it?

Well, real mental illness is no joking matter for anyone, not the person suffering from it, or anyone too nearby. Wouldn’t it be nice to know if that person you’re wondering about is just having a few problems or actually qualifies as a sporadically lovable psychopath who needs professional help? Watch.

Kevin Dutton is a research psychologist at the Calleva Research Centre for Evolution and Human Science, Magdalen College, University of Oxford.