Size matters. But when it comes to the size of balls, bigger is definitely not better.  According to a new study published in the journal Proceedings of the National Academy of Science, men with larger testicles may be less caring and involved fathers. Here's how that works:

Big ol' balls= more sperm production

More sperm = more testosterone (generally)

More testosterone = tendency to focus energy on mating, not nurturing children

MRIs of test subjects frrom the study also revealed that men with higher levels of testosterone also showed less activation in the reward centers of their brain when shown pictures of their children. The same men who went less gaga about their kids tended to have more hands-off parenting styles, too.  This suggests that men with more testosterone (and balls) might be biologically less interested in parenting.

Okay, so if men with bigger balls and more testosterone are less invested in parenting, would this guy be the worst Dad ever?