Turns out, it's not about the size of the man's hand, it's about which finger is taller: the index or the ring finger. 

If you're checking out a man with a bigger ring finger, he's packin' some heat and is ready to fertilize you any second.

True or false with your situation? I asked some guys on air and they all said their index finger was bigger and that it was wrong... but of course they're going to say that.