So I couldn’t resist commenting on this story at Gene Expression about how smarter people have less sex. Tyler Cowen’s original post on the subject can be found here but it’s the analysis from the first link that I really wanted to talk about. In particular the arguments made suggesting that more intelligent individuals have a lower libido are particularly dubious.

For instance here is the primary argument that individuals with high IQ may have lower libidos (emphasis/links from original):

Perhaps more revealing, HS, also showed that intelligence correlates with less sex within marriage for the same age range. While still consistent with pregnancy fears and competing interests, lower sex drive seems like a better fit. In fact another revealing finding from the Counterpoint survey was that while 95% of US men and 70% of women masturbate, this number is only 68% of men and 20% of women at MIT!

Looking only at MIT seems to be a huge biasing factor given that we know foreign students are massively overrepresented at MIT. With many students coming from societies with more traditional attitudes (or just different) about sexuality it would be an error to try and chalk up these differences to intelligence. Still intuitively it seems plausible that nerds (rather than smart people in general) masturbate less than other groups but a much better explanation for this is that sexual experience makes people comfortable with sex. It stands to reason that having had regular sex in a relationship would make one more comfortable with your sexuality than you would have been if you had remained a virgin. In other words there is no reason to believe that the lack of masturbation at MIT causes the lack of sex at MIT rather than vice versa.

The study about sex during marriage is equally uncompelling as it only gives self-reported sexual frequency. Thus this could just as well reflect a correlation between lower intelligence and exaggeration of sexual frequency. Either because of a desire to live up to some macho ideal or simple self-projection of a ‘normal’ amount¹ of sex². In any case it isn’t very conclusive.

Finally let’s look at what Gene Expression cites as the supposed explanation of this effect:

So intelligent people have lower libidos and less masculine physiques. What hormone is responsible for both sex drive and masculine builds? That’s right: testosterone. And two new papers suggest that testosterone may depress IQ. One team found that salivary testosterone levels were lower for preadolescent boys with IQs above 130 and below 70. (the same two groups most likely to be virgins in adolescence)

While there seems to be some fairly compelling research connecting testosterone levels in the low male range/high female range with high intelligence the correlation between Testosterone levels and sex drive is weak and it’s far from obvious that adding more Testosterone to healthy individuals would increase their sex drive.

Also I want to challenge the duality proposed between people with higher intelligence being more sexually conservative or more sexually adventurous. It can both be true that smarter people are more likely to visit a prostitute (there is a larger high risk tail) while the median individual is actually more sexually conservative. I’ll avoid giving personal examples here but based on the people I know this certainly seems like a reasonable possibility.

Ultimately I’m not sure why smarter people end up getting less sex. I suspect some of it has to do with being told they are less sexually desirable, either directly by reducing their pool of sexual partners or indirectly by reducing their confidence. But it could also be that most sex is the result of bad judgment (drunk party sex) or girls being pressured into sex and smart girls/guys are less susceptible to these things. It could be a lot of things but right now we don’t have much hard evidence for any of them.