My (CPR) recent post in response to Satoshi Kanazawa's musings on the sexual appeal of "fat chicks" seems to have touched a bit of a nerve. Not a major nerve, but still...
One of the critical responses cited a famous study in evolutionary psychology, by Clark & Hatfield. Rather than bury my response in the comments section, I've posted it here for anyone who might be interested in one of the debates over methodology in the field. "Jason's" comment mentioned the study.
The Clark and Hatfield study is, as you say, famous, but that doesn't make it a good study. In fact, it provides another prime example of the shoddy reasoning in evolutionary psychology that ends up making the whole field seem much weaker than it is:
Clark and Hatfield (1989) used "attractive" undergraduate college students at an American university to approach other students on campus, asking if they would like to go to bed with them. Most of the males immediately agreed to the offer of no-strings sex. Most of those who didn't asked for a rain check. Meanwhile, drum roll please, none of the women approached by strangers offering their services accepted. This study is widely cited (as by Jason) as evidence that men are more into casual sex than women. In general. Universally. It's part of our nature, you see.
Let's think about this for a moment.
American undergraduate students are typically between 18 and 22 years of age. Janus and Janus (1993) found that the majority of even the youngest respondents to their surveys had had their first full sexual experience between the ages of 15 and 18 (70% of males and 68% of females), while a significant number of both males and females didn’t have their first experience of intercourse until they were between 19 and 25 (9% and 16%, respectively).
So we can be confident that most of the young Americans who were approached with the offer of spontaneous sex were either in their first years of sexual activity or had not yet had commenced an active sexual life.
These folks are typical examples of "men" and "women?"
In what sense then can their responses be taken as being representative of male and female sexuality? Blum (1997), Hite (1987), Kinsey and colleagues (1953), Sherfey (1972), and many others have noted that women, in particular, experience dramatic changes in their sexual feelings as they age. In commenting on women’s sexual histories, Kinsey, Pomeroy, and Martin (1953) observed:
"One of the tragedies which appears in a number of marriages originates in the fact that the male may be most desirous of sexual contact in his early years, while the responses of the females are still underdeveloped and while she is still struggling to free herself from the acquired inhibitions which prevent her from participating freely in the marital activity. But over the years most females become less inhibited and develop an interest in sexual relations, which they may maintain until they are in their fifties or even sixties. (pp. 353-354)"
Thanks to research like Kinsey’s, it has become common knowledge that a woman’s sexual peak occurs somewhere around her early 30s (though precisely what is meant by this term remains somewhat vague). It is also well-demonstrated (e.g., Hite, 1987) that safety is an important consideration for women to feel sexually at ease. In the United States in particular, where there is a relatively high incidence of sexual abuse against women (Janus & Janus, 1993), young women being approached by unfamiliar men inviting them to bed would be wise to be extremely suspicious.
Over fifty years ago, sex researchers Ford and Beach flatly declared that, “In those societies which have no double standard in sexual matters and in which a variety of liaisons are permitted, the women avail themselves as eagerly of their opportunity as do the men.”
In addition to the questions of age and safety, this study is a good example of the sometimes bizarre lengths researchers will go to in order to demonstrate a point. Thomas Kuhn (1962) famously described this sort of investigation, “Rather than resembling exploration, normal research seems like the effort to assemble a Chinese cube whose finished outline is known from the start” (p. 262).
My point is that this study was done in a cultural context in which it is virtually unheard of for strangers to approach anyone (other than movie stars or fashion models) with a sincere solicitation of sexual relations – much less in broad daylight and with none of the disinhibiting effects of alcohol. That all of the women smelled a rat is far less intriguing than the fact that so many of the young men accepted the bizarre offer, which a moment’s thought would have shown to be too good to be true.
There are scores of societies around the world where offers of casual sex are cooly accepted (or not) by women and men without a problem (our book contains a discussion of many of them).
Rather than confirmation that women are universally less interested in sex than men, this study – cited in every one of the popular books of evolutionary psychology I own – appears to offer little more than confirmation that young American male university students tend to be far more reckless than young women – an altogether less interesting conclusion obvious to anyone who has ever attended a frat party.
As in the study Dr. Kanazawa cites in his original blog posting, Clark and Hatfield's famed study does not in fact demonstrate what these authors claim it does, but some scientists (and popularizers in search of public attention) seem to be too happy to have their bias confirmed to bother with such matters. This is the Achille's Heel of evolutionary psychology: because the subject matter tends to attract people who already know what they think, many of them are overly willing to accept research that seems to confirm their position while ignoring its flaws. Thus, a lot of research that wouldn't see the light of day in other scientific fields finds its way to notoriety in evolutionary psychology.
A good segment of the public may buy it (literally), but this is probably the main reason evolutionary psychology is largely dismissed in the scientific community -- a tragedy for those (and there are many) who are doing serious work, using serious methodology.
For those readers who may be interested in other perspectives on Kanazawa's "science" I'd recommend this for a look at his use (or non-use) of statistics and this for a more general critique of a piece he wrote on terrorism a few years back.
Update: Here's an interesting bit of research that raises some important questions concerning the validity of research into female sexuality and the lingering effects of cultural suppression. Women's responses changed dramatically when they thought they were hooked up to a lie-detector.
