Terry Teachout says that “Scientists are forever proving what everybody knows, especially when it comes to music.” Cross out music and replace it with sex, and you’ve also got a substantially true statement. One big advantage to Tim Harford’s The Logic of Life and Dan Ariely’s Predictably Irrational: neither is exclusively about sex or relationships, but both have some unusual experiments. The former discusses how marriage and dating are like markets and how gender imbalances work, while the latter discusses the differences in cognition and choices when in aroused versus unaroused states.

In contrast, Why Women Have Sex gives us a lot of the obvious: women have sex for a variety of reasons, not surprisingly, but the authors don’t go into why a particular reason might predominate at a particular time. The reasons are mostly descriptive instead of explanatory and predictive. Reading the table of contents is almost as good as reading the book: women do it because they’re attracted to the person, for pleasure, for love, for conquest/status, for duty, for adventure, for barter and trade. One could probably figure that out from a few months of reading Cosmo.

We learn that women like men who are tall, have a sense of humor, wealthy, skilled, upbeat, symmetrical, and attractive, the last adjective comprising the earlier ones. On page 22 we learn that “A person’s mood at the time of an initial encounter is an important factor in determining attraction—positive feelings lead to positive evaluations of others and negative feelings lead to negative evaluations.” Really? I had no idea. Notice also the hedging words: mood is an “important factor,” but far from the only one. Later on the same page, we learn that “Having a good sense of humor usually signals an easygoing, fun-loving, adaptable personality.” To my mind, the word “adaptable” is the most interesting word—how does humor signal adaptability?—but the authors don’t pick up on that thread.

The idea behind Why Women Have Sex is to give a large portrait of some of the research findings out there. This is a useful service, and if I were preparing for an academic career in sexuality or sexuality studies, or if I were a journalist who wrote about such issues frequently, I’d buy this book for its bibliography. Even so, however, the book has more scientific trappings than actual science. The introduction states their study was conducted between June 2006 and April 2009 and:

Web links and online classified advertisements requested women’s participation in a study designed to understand sexual motivations. The survey itself was hosted by a database using 128-bit encryption technology to protect the information from hackers and ensure the utmost anonymity to the study’s participants.

The tech terms are poorly used: 128-bit encryption is meaningless without noting the algorithms used, although the authors are probably talking about generic TLS/SSL layers for authentication between client and server. But the larger problem is likely to come from people posing as women who aren’t women and ballot stuffers. Even if they took care of that, they still don’t have a random sample, which would be necessary to draw conclusions about the general population. This means the conclusions that they do draw from their sample aren’t useful. For more on why this is important, take a look at almost any introduction to statistics textbook; the upshot is that their data is suspect, which undermines the book’s conclusions.

I read the first third of Why Women Have Sex closely anyway, and some claims aren’t cited in their bibliography. For example, page 14 says that “DNA fingerprinting studies reveal that roughly 12 percent of women get pregnant by women other than their long-term mates, suggesting that some, but certainly not all, women pursue this dual mating strategy.” That seems improbable, which made me curious about the study backing it up. Page 14 has two research citations; neither relates to this claim.

To me, the biggest reminder Why Women Have Sex offers is why literature retains its power over time while pop sexuality books fade like flowers against the onset of winter. Literature can withstand the onset of cold time because it tells us something that can’t easily be captured by survey; to me, Madame Bovary, The Unbearable Lightness of Being, and Alain de Botton’s On Love have vastly more explanatory power and aesthetic interest than Why Women Have Sex. I’m reminded of this passage from Robertson Davies’ The Lyre of Orpheus:

But Darcourt was not disposed to Freudian interpretations. At best, they were glum half-truths, and they explained and healed extraordinarily little. They explored what Yeats called “the foul rag-and-bone shop of the heart”, but they brought none of the Apollonian light that Yeats and many other poets cast upon the heart’s dunghill.

I quote Davies quoting Yeats: there’s a very fine movement of thought there, which Why Women Have Sex lacks. Even a book like Neil Strauss’ The Game: Penetrating the Secret Society of Pickup Artists offers more explanation, and it doesn’t even have the backstop of the many but still incomplete peer-reviewed studies offered by Why Women Have Sex. In short, there are more useful ways of looking at the questions this book asks. Try reading this interview with the authors or looking at some of the other books mentioned and you’ll begin to find those more useful ways of knowing.