In the never-ending quest to help people co-exist peacefully with their spouses, children, siblings and in-laws, therapists are turning to tools used to assess the psychological stability of pilots, police officers and nuclear-power plant operators: personality tests.

I'm not talking about the pop quizzes in magazines that claim to help you determine the color of your aura or what breed you'd be if you were a dog. I am referring to tests that are scientifically designed and heavily researched, consisting of dozens if not hundreds...