Friday Weird Science: The big deal on penis size

Apr 12 2013 Published by under Friday Weird Science, Uncategorized

Sigh. The penis story is now 5 days old, and I'm only just now getting to it. Sci is sad and behind the times, but that's because I don't get the awesome press releases that so many journalists are heir to. The joys of academia, I'm the last to hear about the penis study!

The coverage was so...BIG...that Knight Science Journalism Tracker has a whole pile of links. Science News, NBC (complete with the quote of the day "The human male possesses the Italian designer faucet of penises"), National Geographic. Gawker.

So after all this coverage, I went eagerly to read the paper. I mean, this must be a big deal, right?

But really...I'm not sure why all the penis coverage. I admit it's tough to give up a penis in PNAS joke, but I'm not sure what makes this meaty, shall we say. I think what they did is fine and well controlled, met all the standards of scientific rigidity, but I'm not sure they...went all the way. The conclusions were, well, kind of expected, and a little limp.

You see where I'm going here.

Mautz et al. "Penis size interacts with body shape and height to influence male attractiveness" PNAS, 2013.


I think we've all heard that "it's not the size that counts, it's how you use it!". And we all ALSO heard that "no really, it's the size that counts". But is it?

Male penises are out there. They are loud, they are proud. Rather than the retractable penises of some other species (poor ducks have to hide their light under a bushel, due to sheer physiological impossibility otherwise), the human male's penis stands out.

Really, the authors say it better than I can:

The upright body posture and protruding, nonretractable genitalia of male humans make the penis particularly conspicuous, even when flaccid. This observation has generated suggestions by evolutionary biologists that the comparatively large human penis evolved under premating sexual selection (19, 20).

(Let us all pause a moment, and dream of how neat and wacky it would be if humans had retractable penises...)

So the question is: do women think bigger is better? And is this a result of sexual selection?

After all, there was a time before clothing. A time when all went proud and free (or possibly shivering and free, depending on conditions). And during that time, with those stand-out penises...well you're going to get judged. So DID women judge? What there sexual selection? And does this mean that men were the first to invent clothing out of sheer self-defense?!

Obviously other studies have asked women about their penis preference. Some say longer. Some say wider. Some say size doesn't matter. And at least some of these people are lying. After all, while there's a lot of social pressure for men to be packin', there is just as much social pressure for women to say "oh honey, you know I don't care about THAT!" And when you have a questionnaire...well it's hard not to be generous. Or less generous, depending on your mood.

And how do you STUDY the role of penis size in attractiveness? Previous studies just took one drawing of a guy, and changed his penis size. While that might isolate the penis itself, it doesn't really give you a picture of how the penis stands (so to speak) among other bodily traits, like shoulder-to-hip ratio (broad shoulders and narrow waist = more attractive) and height (tall = more attractive).

So the authors of this study made computer generated images, where height, shoulder-to-hip ratio, and flaccid penis length all varied, based on a wide sample of men. They had a group of 105 women look at the figures (there were 343 in all, so they had all possible combinations of penis size, height, and shoulder-to-hip ratio), and had the women rate the attractiveness of the figures. They also looked at how long the women's eyes lingered on the images. Just in case.

penis size1
(This figure kind of looks like an art installation to me)

And DID it show that bigger is always better? Well...yes, but the BIGGEST effect was actually in shoulder to hip ratio. Men with shoulders that fill doorways and small hips were the most attractive, and this body shape was the MOST IMPORTANT variable in determining attractiveness. Not penis size. Body shape.

Penis size came up short (heh), in second place, roughly tied with height. In fact, it scored a little BELOW height in the linear selection gradient. The Shoulder-to-hip ratio linear selection gradient was 1.020, while the penis size was 0.249 and height was 0.269. So while yes, size does matter, it doesn't appear to matter as much as other determinants of attractiveness. Worried men, you can relax. As long as you're tall, and have broad shoulders and a narrow waist. Or clothing. Clothing works, too.

And really, it doesn't even seem like it's the size that counts, it's how you use it the proportionality. The penis has to look proportional or better. If a super tall guy has an average penis, it doesn't look proportional, the bigger penis is needed just to look the right size all over. The size is important in relation to the other traits. And for taller men, the larger penis served them better than for shorter men. Size can only make up for so much, apparently.

Interestingly, this study actually had a lot more to it than penis size (not that the media reported on any of it). It looked at how the WOMEN related to the men they picked as attractive. Taller women? They rated taller men as more attractive (there's a lot of pressure there, no matter what novels you read, the lady is always supposed to look up at the man becomingly through her lashes, and this becomes increasingly hard to do as the poor damsel approaches 6 feet). Heavier women showed a larger effect of penis size on attractiveness rating (does that mean anything?). There was no effect of menstrual phase (though the authors note that they didn't actually check the fertility phases) or of the pill (which is interesting in itself).

The authors also found that the relationship between penis size and attractiveness is non-linear.

penis size2

You can see here the attractiveness ratings (controlled for height and shoulder-to-hip ratio, so just based on the peen) as a function of size. At first ratings go up quickly, but after about 7.6 cm (3 inches, keep in mind these penii were all flaccid), the slope decreases. Though I'll note they never reached the peak. I'd be interested to see whether the attractiveness forms an inverted U shape when you get above, say, 17cm. I mean, if it practically IS a third leg, how attractive is that really?

The conclusion is that...size matters. Size matters, in fact, about as much (thought slightly less than) height. But what really matters? Shoulder-to-hip ratio. But I guess "Shoulder-to-hip ratio counts most!" Doesn't make NEARLY as good of a headline.

And WHY does size matter? Well obviously they didn't investigate that, but they hypothesize that larger penises may lead to better vaginal orgasm and that's totally why the ladies like 'em large. I'm pretty skeptical of this, considering that a relatively small percentage of women have HAD vaginal orgasms. I'd be more likely to hypothesize that a larger member might go along with a larger everything else. Larger penis? It's a good bet he's tall. Tall? It's a good bet he's healthy. So if there is sexual selection going on here (which this study can't conclusively claim, it can only show that size matters in attractiveness), it could well be for the other traits first, and the penis is merely another indicator.

But there are two issues I have with this study: First, the population. All the viewers were heterosexual women (yeah, ok), and they were all Australian. I've never heard anything that speaks particularly to Australian opinions on penis size, but this is a Western culture we're dealing with, where we are told since middle school that bigger is better. So I'd be very interested to see how much of this is a cultural phenomenon. After all:

...novels, magazines, and popular articles often allude to the existence of a relationship between penis size and sexual attractiveness or masculinity (21, 22). Many cultures have fashion items, like penis sheaths and codpieces, that draw attention toward male genitalia.

There is a very large culture around the penis, is what they're saying. Some may be biology, yes, but how much is penis culture?

The second issue I have is...well the study didn't go all the way, as it were. The women only rates the attractiveness of FLACCID members. Not erect ones. Presumably, if, as the authors argue, females can see the male's...morphology...all the time, they'd see it in various states of arousal. Wood happens, you know? And there is, of course, the phenomenon of "showers" vs "growers". The concept is that some men "grow" during an erection while the flaccid penis is unimpressive, while others "show" with an eye-popping flaccid penis that then doesn't inflate as much. I actually don't know if this phenomenon exists, or if it is merely hearsay (SOMEONE needs to study this. It's not THAT hard...oh wait...I guess in some respects it's hard...), but if it does exist, it would be an interesting question: what about the size of the erect penis? How does that rate in terms of attractiveness (once you get over the inevitable giggles involved in looking at hardons in silhouette)?

And in the end...did this study really blow us out of the water with new information? Penis size matters...but only in the sense that the overall package matters, and overall, the shoulder-to-hip ratio matters a whole lot more. A man's attractiveness is more than his penis, but hey, a good penis can help. Stop the presses!

Now, I'm not saying the study is bad! It's fine! It's well controlled! I really love that they pulled in the shoulder-to-hip ratio instead of just studying penis size, I think it gives a much better picture. But you know, I feel like it didn't go all the way to answer the question. I felt like the study could have been more substantial, had more girth...I could go on.

So really, I can only conclude that the reason this study got so much coverage is because...well it was about penis size. And size matters! Really, who needs another reason? I can't fault them, I never do! 🙂

26 responses so far

  • figleaf says:

    Hi Sci,

    As a guy the first thing that jumped out at me (ok, not as good at the weenie humor here so that's the closest I could get) is that they only queried women.

    The assumption being, at least according to the Scientific American post about it, that humans extra prominent penises got that way via women's preference. Which I suppose could also be true about shoulder-hip ratios and height. But I'm sticking with penises (still can't do the humor thing) because that's what everybody's hung up on. (Getting better with that one.) And anyway, I think it's significant that out of the three variables measured everyone is talking about the penis part.

    Anyway, what jumped out at me was that in practice men seem waaaay more concerned about (other men's) penis size than women seem to be. Not that women aren't interested, just not nearly to the same degree.

    For whatever reason, at least in the same societies you're likely to find Australian women, penis size is a *huge* marker of status (and insecurity) in men. And by the way I'm talking about hetero men here, which is why my ears perked up with I saw the study measured preferences for flaccid penises rather than erect ones. Which men are more likely to encounter socially, especially hetero men.

    So my eminently testable hypothesis would be that a graph of hetero men's preferences would tend to be linear rather than u-shaped. Definitely for penis size. Very likely for shoulder-hip. Probably height too. Because while we really don't often compete physically for status we do tend to defer to each other based on those dimensions.

    Here's the kind of deference I'm talking about. Men are amazingly likely to say of a woman who's "out of their league" that they "probably have a boyfriend who could break me in half." Since in fact this common assumption by men isn't actually particularly true -- even when they're big attractive women's partners are rarely physically aggressive. But! There's that hetero male deference to size I was talking about: it's more about male-male competition than female mate preference.

    Anyway, I'm obviously still just guessing here but the cool thing is the researchers already have everything they need to confirm or refute me: run the exact same test on 105 hetero Australian men and see what shakes out. With luck they'll try it. And let us know.


    • scicurious says:

      Hi Figleaf!

      I see your argument, but even if men have always been concerned about their penis size...WHY are they concerned? And does the concern give them any control over the sexual selection that may or may not be taking place? Even if a dude is smaller than another dude...does that have anything to do with competition? How do we know the well-endowed guy would win the fight? I'm just not sure that male-male competition could account for the difference, you know?

      • Brock says:

        > WHY are they concerned

        Because they know women judge them on this. And hetero men don't care about another guy's size. Unless your new girlfriend admits past lovers were bigger. Then he cares.

      • figleaf says:

        Hi Sci,

        I have no idea what the mechanism would be.

        But then I'm not the one who said "The finding suggests that women’s preferences could have fuelled the evolution of the human male penis."

        Like the joke about the bear and the guy putting on running shoes so he could outrun his companion, my hypothesis doesn't have to be the best -- it just has to be better than the current proposal. And as you say the current proposal is pretty weak tea.

        And so I'd like to see them run the experiment on men to see how those results were interpreted in the popular press.


  • Tara Malow says:

    This was *excellent*! Thank you for such an articulate critique of the study and the media coverage. The points you made were things that were bugging me about the story (especially the cultural perspective).

    * giggling helplessly at the puns *

  • Anonymous says:

    There needs to be a study that offers a fourth option: "penises are just silly-looking"

  • BJ Nicholls says:

    Sounds like women are attracted to ancient Minoans (at least as they were painted). I'm guessing that guys that can "bull vault" are even hotter. Ancient Egyptians were pretty slim-hipped and wide-of-shoulder too if you believe the glyphs. And they had such cool hats.

  • Regis says:

    This is a HILARIOUS post, first of all.

    Secondly, I am not surprised by the magnitude of the importance of hip-to-shoulder ratio. That particular look is visible in the silhouettes of comic book heroes and even old portraits of royalty. I wonder if men have a similar ratio they find attractive - perhaps hip-to-waist-to-bust.

    • scicurious says:

      Oh yes! There's well documented preference for a 0.7 waist-to-hip ratio in women. Nothing in the bust. Just the waist to hip.

  • Jay says:

    Best review so far - this actually 'explained' the results - 'all' the other ones (ok, 2 articles...) just parroted the results - results which to me seemed rather contradictory and non-conclusive..

  • cactusren says:

    This is anecdotal, I know, but I can vouch for "growers" vs. "showers" being a real phenomenon (n=2). An actual study that could quantify the average amount of change, the variance, etc., would be great, but there does seem to be a continuum between the two.

  • Nikos Solounias says:

    penis size is limited by the power of the heart to pump - otherwise women would be selecting an ever larger one

  • Bob says:

    I'm pretty sure the grower vs. shower thing is real. There's a lot of variance in penis other than simply size.

  • rshoff says:

    Wow, really enjoyed reading your article. Thank you!! It's entertaining AND more forthcoming than the news agencies' rendition of the study. You covered the territory very well and very delicately.

    I'd like to pipe in that if the study is to measure attributes that determine attractiveness of men to the opposite gender for mating purposes (much the way we may study monkeys or slugs) then I would expect the study to do the evaluation from the top down (so to speak). Penis size being one of many human attributes that coalesce into that thing we call sex appeal, but taken alone, it is an offensive question not worthy of social science.

    And I do find it easy to believe that the shoulder span to waist size ratio is right up there at the top for physical sex appeal chart. But I think most women already have that figure out. They don't need a study for that. And then there's personality, status within the tribe, compatibility, etc, etc etc... I think we can give women more credit than being hot to trot maniacs running around with a tape measure looking for a sex partner.

    I think the real danger with hyping superficial studies like this is that it is feeding into an extremely sexualized youth pop culture and encouraging them to continue to make bad choices around sexuality. And for what? What do we gain from studies like these?

  • Malehanger says:

    Yes, "studies" like these are in fact always biased to some degree and flawed as well. I have yet to come across a similar study which was not.

  • Torbjörn Larsson, OM says:

    "penis size is limited by the power of the heart to pump - otherwise women would be selecting an ever larger one".

    I don't think the mechanics works out that way, unless you are thinking about blood supply. But the likelihood for defects (leakage) would increase with size. Which amounts to teh same conclusion: better making the hard choice of "not too long"! =D

  • Vanessa says:

    Are you a scientist ? A writer, you surely aren't

  • Ana Mercedes says:

    Let me give you my humble opinion. Ok, I am not a scientist, but as an independent escort I get to see more penises than the average woman (or scientist, for that matter), which makes me an expert of some sort. First, it seems to me that the question of whether penis size matters or not is a question that mainly matters to men. Most women I know, including myself, find the discussion boring. Second, the results of the study seem to have been overblown in the press. Penis size is not the most important trait and it interacts with other attributes to determine male sexual attractiveness. Third, the test was done with flaccid penis size. Well, let me tell you from experience, it is not easy to predict what a flaccid penis looks like when erect, and what woman in her right mind would attempt to determine sexual attractiveness by studying a flaccid penis? Fourth and most important of all, even if it were true that penis size is statistically significant, this does not mean that it is significant in real life. There are more important traits that make a man attractive; traits that the study completely ignores. Have you seen the computer-generated images of naked men that were used in study? These are not men! More like robots with penises. What about a pretty face, a nice refreshing smile, and even more important for male attractiveness, a beautiful and charming personality? These are qualities that I value more highly than what the researchers around Professor Mautz studied.

    So boys, don’t worry! Penis size is not what really matters. Penises come in all sizes and penile preferences in women differ, if they care at all. But more important, there are more important qualities in male attractiveness. And penis size does not even matter that much when it comes to sex. For really good sex, a man needs to get more involved than with his penis. And that’s again where other qualities matter, including personality.

    Ana Mercedes

  • Rebecca says:

    It DOES matter, just watch this video from MTV

  • Sherita says:

    Wow, this paragraph is fastidious, my sister is analyzing these kinds of things, thus I am going to convey her.

  • Randy says:

    The women's response to shoulder vs hip width, the classic male "V" shouldn't surprise anyone. Nor should the male response to a .7 waist to hip ratio in women.

    According to an article I remember from Scientific American about twenty years ago: In women fertility is directly, related to this .7 waist to hip ratio, fertility decreases rapidly as a woman's figure moves away from this target.

    It might be a good research project to do a study of sperm viability levels and mobility as a function of the shoulder to hip ratio in men. I'm pretty sure there is a high correlation.

    • Pedro cerrano says:

      You god something dandy going randy!

      I guess it is something tabooed to study so they dont. Imagine if you developed a formula that can say the level of fertility of one individual, it would be unfair and socially unacceptable, but the funny thing is we do it in our heads all the time...

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  • Aron says:

    I already tought wait to hips would give most variation. The % penis is indirect of erect one which it correlates to.For erect I expect flaccid/correlation is the%

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