Research has suggested that marriage has a positive effect on most men—causing them to curb not-so-becoming behavior like smoking, excessive drinking and habitual gallivanting on the town with the guys—but a 19-year study shows that becoming a dad in particular significantly decreases a man's bad habits.

"This research suggests that fatherhood can be a transformative experience, even for men engaging in high-risk behavior," says David Kerr, assistant professor of psychology at Oregon State University and lead author of the study. It seems that, with the arrival of Daddy’s Little Girl (or Boy!), comes the desire to step up and be the father he or she deserves.