A piece of medical news made the rounds last week with the kind of fodder that makes Web editors dance for joy: the kind of material that demands some choice, search-engine friendly punning in the hed.
“Choose Dads With Smaller ‘Nads,” was the title of a Time Healthland post covering a study released earlier this month demonstrating an inverse correlation between testicular size and parenting abilities. But it’s hard to convey nuance in the face of such incendiary, giggle-inducing copy. “As with other seed-bearing nuts, testicle size determines how much juice is produced, and it seems there’s a kind of law of diminishing returns at work,” wrote Time. “The greater the semen output in each ejaculation, the smaller the parenting output later on.” The Los Angeles Times jumped on board (“Men with smaller testicles make better fathers”) along with USA Today (“Size matters.”)
Now before we all go selecting potential mates based on hed alone, let’s examine these news tidbits a bit deeper. As with almost any scientific finding, the results are only incrementally significant—which means they have to be viewed within the larger paradigm of previous studies. Though many studies have demonstrated different parenting behavior correlating with the quantity of a man’s testosterone, this is the first extrapolating the idea to testicle size. Which means, importantly, that it’s only demonstrating a correlation between a man’s balls and his parenting abilities, not causation. This distinction is even incorporated into the title of the original study, published in Proceedings of the National Academy of Sciences as “Testicular volume is inversely correlated with nurturing-related brain activity in human fathers.”
Any number of things beyond testicle size could account for the correlation in this one particular study, a point brought up later on in the Time post.
“We don’t know the direction of the causality,” [study author James Rilling] admits. “It could be that as men become more involved in caregiving the testes shrink.” But he believes it’s more likely that guys with a little less in the sack are a little better with the crib.
Additionally, the study’s authors aren’t even really talking about “parenting skills,” they’re talking about the engagement of a region of the brain correlated with “nurturing” during an fMRI scan—another form of inquiry laden with journalistic misinterpretation.
It might all be in good fun (and a burst of Web-busting unique views for shoving gonads into your lede), except that, as Gary Schwitzer points out in a Health News Review post, “This is the kind of news coverage about a study that results in science and journalism about science losing credibility.”
As Schwitzer writes, a blog post from Emory University, where the study was completed, provides the most balanced rundown of the correlation’s caveats:
“We’re assuming that testes size drives how involved the fathers are,” Rilling says, “but it could also be that when men become more involved as caregivers, their testes shrink. Environmental influences can change biology. We know, for instance, that testosterone levels go down when men become involved fathers.”
Another important question is whether childhood environment can affect testes size. “Some research has shown that boys who experience childhood stress shift their life strategies,” Rilling says. “Or perhaps fatherless boys react to the absence of their father by adopting a strategy emphasizing mating effort at the expense of parenting effort.”
Still, since the study’s publication, any number of outlets have reported on the findings with misleading, punworthy pieces. There’s CBS News (“Men with smaller testicles may be more nuturing dads”) and the Boston Globe (“Do better dads have smaller gonads? Wacky study suggests, yes”). Or Discover (for shame) which reported “the heftier the sack, the results show, the less loving and engaged the pops.”