TL;DR -- She's Just Not That Into You

Psychological Science, February 2012 -- "The Misperception of Sexual Interest," Carin Perilloux, Judith A. Easton, David M. Buss.


As every human knows, it can be hard to know when someone likes you.  We end up devoting a lot of cognitive effort (and song lyrics) to figuring out who would like to have sex with us, and dealing with the consequences of these beliefs.

In this study, Perilloux and colleagues set up a speed-dating situation, while also having each participant provide various ratings (including attractiveness and sexual interest) of each person they met, as well as self-ratings.  This way, they were able to contrast each partner's perception of the other and see how well they matched, or mis-matched. 

They found that men tend to overestimate the sexual interest of women, but that women tend to underestimate the sexual interest of men.  Also, the more attractive a man is, the worse his estimates of interest get, this despite the fact that women tend to also have more genuine interest in more attractive men.  When a woman is rated as more attractive, she's more likely to be misperceived as displaying interest in a man.

So far, so good.  This is a pretty interesting finding, and has implications for understanding complex behaviors such as rape.  However, the researchers try to explain the findings using an evolutionary framework, which I find unnecessary. 

Objection number one: they looked exclusively at an undergraduate sample from the University of Texas (mean age: 18).  You could argue that, as people in their reproductive primes, this sample should be most representative of our evolutionary heritage.  But still, American undergrads are poor representations of the majority of humans on the planet, living or dead.  I always like to see some extensions to different populations before I'm comfortable with an evolutionary hypothesis.

Objection number two: the evolutionary theory isn't needed.  For instance, they try to explain why more attractive women would be more likely to be misperceived as interested by attributing this to an evolutionary bias based on the correlation of fertility and attractiveness.  But this could also be explained by, essentially, wishful thinking.  Our desire for something to be so can influence our estimation of its likelihood.  A cognitive explanation can substitute for an evolutionary one.  And likewise with the difference in over-/under-estimation between men and women: this could be a difference in set points based on the level of sexual interest in the individual him/herself.  Or the finding that more attractive men overestimate more (over-overestimate?): well, as it's pointed out, they also have more success than less attractive men, so could this just be driven by learning?  More frequent reward leads to greater perception of interest, more frequent punishment leads to less?

The authors need to do a better job setting up the kind of background necessary for an evolutionary explanation to be sensible.  Is accuracy of perception of sexual interest linked with differential fitness?  It's not really clear; it's briefly alluded to and glossed with citations -- all of which are connected to one of the authors (Buss).  But this is a prerequisite for making a claim that a trait has evolved!

Overall, there's nothing in this study that couldn't be explained through more fundamental cognitive or learning mechanisms.  Does that mean an evolutionary explanation is wrong?  No.  It just needs more convincing evidence.