Study suggests most men are too small for most women (Part 2)
A 2015 study investigated women's preferences in penis size using 3D-printed cylinder models. The results showed women overestimated the average penis size and preferred penises even larger than that.
Researchers from the University of California conducted a unique study on women’s preferences in penis size in 2015 using 3D-printed cylinder models.1 The most striking results of the study were largely overlooked by the authors: the women who participated significantly overestimated the average penis size in the male population, and preferred penises larger than even their own overestimation of the average. In this review, I critically examine this study and highlight these overlooked results.
⬅️ Previous part
In the first part, I delved into the study design and who the participants were.
🤥 Result #1: Women overestimate the average penis size
The women who participated in the study were asked to choose the 3D cylinder model closest to what they thought the average penis was in the male population. Only 69 out of the 75 participants completed this task. The average estimate for penis length was around 5.75 inches. Only 46% of the respondents estimated the average length to be 5 or 5.5 inches. 48% thought the average penile length was above that, and 6% thought it was under. One woman picked an 8-inch model for this question.
There is an important nuance here that was completely missed by the study’s authors. In the scientific literature, the estimates of erect penile length in the male population take into account the suprapubic fat layer that lies between the pubic bone and the base of the penis at the surface of the skin—the “bone-to-tip” estimate, as it’s called. When one says that the average penile length is somewhere between 5 and 5.5 inches, which is the most credible estimate from the scientific literature, part of that length is the invisible portion of the penis that is hidden beneath the skin. This invisible portion can be anywhere from 0.5 to 1.5 inches in most people, depending on their body composition.2
When women think of penis length, they generally think only of the visible portion of the penis, excluding the suprapubic fat pad—or “skin-to-tip” estimate, as it’s called. Thus, when the participants picked a 3D cylinder model for what they thought was the average penis size in the male population, they were actually estimating the skin-to-tip length. This means that the results have to be adjusted for the suprapubic fad pad length to yield bone-to-tip estimates. For instance, a woman’s pick of a 6-in cylinder would correspond to an actual bone-to-tip penile length estimate somewhere between 6.5 and 7.5 inches.
The histogram must therefore be shifted to the right by the suprapubic fat pad length, which varies between 0.5 and 1.5 inches. This yields an estimation of the average penile length by the women who participated in the study of 6 to 7.25 inches. If the average suprapubic fat pad length is taken to be 1 inch, then women’s estimation of the average bone-to-tip length in the male population was 6.75 inches. This means that the women overestimated the real average bone-to-tip penile length—or at least the closest estimate we have of it in the scientific literature—by approximately 1.5 inches. Based on this premise, only 6% of the respondents actually chose a model that was, bone-to-tip, 5 or 5.5 inches, while the rest picked a cylinder longer than that.
The finding that the overwhelming majority of participants significantly overestimated the average penis length in the male population, even with a study design that provided them with 3D cylinder models they could touch and manipulate, suggests that the phenomenon of “girl inches” isn’t simply a matter of inaccuracy in women’s estimation of a male partner’s size; it could be that women do, in fact, believe that the average penis is bigger than it actually is. If that is true, why is it so?
Perhaps the women who participated in the study were basing their answers on their own personal experience with penises. In other words, they could have been—at least partly—estimating the mean value of penis size from the pool of their past sexual partners. If this pool isn’t a uniform sample of the male population at large, then the women who participated in the study were actually answering a different research question than they were asked.
Given women’s preferences in men, and everything that is known about men’s penis size anxiety, it’s very unlikely that the past sexual partners of the women who participated in the study were uniformly sampled from the male population. It would be safe to assume that, on average, men with shorter-than-average penises have fewer sexual partners than men with larger-than-average penises, especially in a college or university environment such as the one where the study was conducted. If this speculation holds, then the distribution of those women’s past sexual partners would be skewed toward larger penises.
If that holds, then it’s not surprising that the women who participated in the study estimated a mean value for penile length that was significantly larger than the real average in the male population: they were simply working with a biased sample of the data. Thus, asking women to estimate the average penis size might actually amount to asking them to average out all the penises they’ve sexually interacted with—a different research question indeed.
To elucidate this confusion, it would have been sound to control for the confounder by explicitly asking the women in the study to estimate the average penile length of their past partners only. The questionnaire did include similar tasks, where the women were asked, for instance, to select cylinder models for the biggest and smallest penises they had intercourse with, and for the penis they had the best sex with. Comparing the women’s estimate of the average penis size in the male population and their estimate of the average size of their past partners would have been insightful.
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➡️ Next part
In the next and final part, I delve into the women’s preferences in penis size.
Prause, Nicole, et al. (2015). Women’s Preferences for Penis Size: A New Research Method Using Selection among 3D Models. PLOS One, 10(9), e0133079.
Wessells, Hunter, et al. (1996). Penile Length in the Flaccid and Erect States: Guidelines for Penile Augmentation. The Journal of Urology, 156(3), 995–997.