My mother always told me to date a guy who was nice to his mother, and I have done that. I have also the opposite of that. In my own personal research, I see a direct correlation between how a man treats his mother and how he treats his woman. (Yes, I just referred to myself as "woman;" I think it gives me some folk-wisdom authority.) Now, there's some science to back it up.
A study that appears in the journal Child Development found that relationships between mothers and sons change from childhood to adolescence, and the closeness between mother and son can affect the child's behavior as a teenager. Perhaps not totally surprising, but potentially useful.
Researchers at several universities monitored 265 mothers and sons from low-income families in the quaint town of Pittsburgh, Pennsylvania from the time the boys were five-years-old through their adolescence. Their findings show that naughty kids (who turned into more rebellious teens) were the same kids who spent less cuddle-time with mom. Also, mothers who were happy with their partners tended to have better relationships with their sons, and in turn, these sons had healthier relationships with friends in adolescence, and likely, beyond.
The study doesn't, of course, tell you how to figure out whether a guy is nice to his mother — in my experience, by the time you've met Mom, it's a little too late. But that's science for you.