The only way to be sure is to give them the Voit-Comp test.
Make sure that you ask every female on the first date if she knows what a tortoise is.
Nossir. You ask them this. "You're in a desert, walking along in the sand when all of a sudden you look down and see a tortoise. It's crawling toward you. You reach down and flip the tortoise over on its back. The tortoise lays on its back, its belly baking in the hot sun, beating its legs trying to turn itself over. But it can't. Not with out your help. But you're not helping. Why aren't you helping? WHY???!?