A new study by researchers at Emory University in Atlanta suggests that men with smaller testicles may be better dads.
Dr. James Rilling and his team studied 70 dads between the ages of 21 and 43, noted the Daily Mail.
Their testicles were measured, and their brains were scanned with a MRI while they looked at photographs of their own child, a stranger's child and an adult stranger.
The men's female partners answered a questionnaire about the dad's involvement with their children.
Dads who were the most responsive to their child's faces also had smaller testicles and were more involved in taking care of their kids, per the questionnaire.
"The link between testes size and parenting-related brain activity suggests a trade-off between mating and parenting," said Dr. Rilling.
The trade-off is that smaller testicles also mean lower amounts of testosterone, which creates a less likelihood of pregnancy.
Source: Daily Mail