Okay, set aside all the jokes and laughs about small balls, because having big cojones may mean you're not a good dad.
At least according to a study by Emory University researchers in Atlanta, men who tend to enjoy being a nurturing parent also tend to have smaller testicles.
The study, released Tuesday in the Proceedings of the National Academy of Sciences, involved 70 men aged 21 to 55 with at least one child under 2 years old.
University of Notre Dame anthropologist Lee Gettler, who studies this effect, told NBCNews, “The general idea is that lower testosterone on a day-to-day basis helps attune fathers to the needs of their children.
Lower testosterone may also make men more empathetic, less aggressive, less interested in mating, or all these.
The Emory group is the first to use testicle size as a physical marker, and to see if testicle size correlates with positive feelings from nurturing as a way to help explain differences in male parenting.
Some doctors are skeptical testicle size really matters. The study researchers admit that it poses as many questions as it answers. Such as, do men genetically predisposed to smaller testicles become more nurturing fathers, or does nurturing shrink testicles?
What do you think dads?