Do Smaller Testicles Mean a More Involved Father?

A new study by researchers at Emory University shows that men with smaller testes are more likely to be involved in the hands-on care of raising their child.

The researchers looked at why some fathers spent less time parenting than others, examining several factors including educational background, income, socioeconomic markers and social skills.  

"Our study is the first to investigate whether human anatomy and brain function explain this variance in parenting effort," first author Dr. Jennifer Mascaro, an anthroplogist and neuroscientist said, whose findings were reported today in PNAS.

The study looked at 70 biological fathers with newborns between the ages of 1 and 2. All of the fathers were living with children and their biological mothers during the study.

Both the mother and father were surveyed regarding the father's hands-on involvement in childcare, including changing diapers, taking the infant to the doctor when he or she was sick and bathing the child.

The researchers then measured levels of testosterone, the male sex hormone. Previous results have shown that lower levels of the hormone were linked to greater parental involvement, while higher levels of testosterone could result in higher accounts of infidelity or divorce.

The findings suggested a small correlation between low testosterone levels and better parenting, according to background information via the study. Findings also note that a father's testes volume corresponded with reward centers of the brain. So fathers with lower amounts of testosterone were more likely to notice a greater activation in reward centers when looking at a photo of their child.

Dads, what do you think?

The study was presented Monday (Sept. 9) at the Proceedings of the National Academy of Sciences (PNAS).