At last night's Republican debate, a new issue surfaced when candidate Donald J. Trump responded to Sen. Marco Rubio's previous remark about the size of certain body parts.
"And he [Rubio] referred to my hands: 'If they're small, something else must be small.' I guarantee you there's no problem. I guarantee," Trump said.
Although news organizations have understandably decided to pass on fact-checking this claim, it does raise a scientific question: Is the size of a man's hands related to the size of his manhood? [8 Wild Facts About the Penis]
There have been conflicting results about this question, said Debby Herbenick, a sex researcher at Indiana University.
Some studies have found a correlation between finger length and penis size, and others have not, Herbenick told Live Science. But these studies look at groups of people, not individuals, she said. Certainly, you'll find people with big hands and small penises, small hands and big penises, and every other combination in the real world, she said.
A 2011 study, for example, suggests that there may, in fact, be a link between hand size and penis size. The study, published in the Asian Journal of Andrology, found that the ratio between a man's index finger and ring finger was linked to penis size. Specifically, the researchers found that having mismatched index and ring fingers (meaning these two fingers are different lengths) was linked to having a longer penis.
The association is not as out-of-left-field as it may seem. Some research suggests that testosterone exposure in the womb may play a role in both penis size and finger length, although more studies are needed to confirm this idea, the researchers said.
How big are we talking?
In a 2013 study, researchers found that the average American man's penis is 5.6 inches (14.2 centimeters) long when erect. But there's a great deal of variability. In the study, the researchers found that the shortest penis measured 1.5 inches (4 cm), while the longest measured 10.3 inches (26.2 cm).
Given the range of sizes, it's no surprise that a European condom company, TheyFit LLC, set out to broaden the playing field in 2011 by offering an array of condoms in 95 different sizes.
But, as the age-old question goes, does size really matter?
According to a 2012 study in The Journal of Sexual Medicine, the answer is yes — well, for some women that is. In particular, women who have frequent vaginal orgasms are more likely than other women to say they climax more easily with men with larger penises, according to the study.
"Male anxiety about penis size may not reflect internalized, culturally arbitrary masculine stereotypes but an accurate appreciation that size matters to many women," study researcher Stuart Brody, a psychologist at the University of the West of Scotland, told Live Science in 2012.
But men need not fret if they aren't well endowed. There's also a great deal of variability in women's size preferences, Barry Komisaruk, who researches female sexual response at Rutgers University, told Live Science at the time.
Another study, from 2013, found that penis size is a bigger factor for taller men. In the study, the researchers found that a larger penis had a greater effect on how attractive taller men were to women.
Of course, on the question of whether size matters for the Office of the President, well … "whatever your genitals look like, it just doesn't matter," Herbenick said.