Thursday, May 08, 2014

Women And Their Eggs. How Ovulation Makes You Act And Other Tales From Evolutionary Psychology.

A new meta-study looks at the vast field of evolutionary psychology studies into menstrual cycle and women's impregnation preferences*.  That term is mine, to cover the field where women are argued to prefer pictures of rough male faces when they ovulate and pictures of smooth and babyish male faces when they don't, and so on.  These preferences are seen as indications of the type of man the woman would prefer to be impregnated by, trading different unconscious objectives:  The rough face provides the best genes but the baby-face is more likely to hang around and help in childcare etc, so women are more likely to pick the rough face to be the baby daddy but let the baby face wear the horns.  And so on.

The menstrual cycle studies even argue that women vote for manly men when they are in the ovulatory part of the cycle.  Or that women wear red or pink when ovulating.

Anyway, the meta study abstract tells us something interesting:

In evolutionary psychology predictions, women’s mate preferences shift between fertile and nonfertile times of the month to reflect ancestral fitness benefits. Our meta-analytic test involving 58 independent reports (13 unpublished, 45 published) was largely nonsupportive. Specifically, fertile women did not especially desire sex in short-term relationships with men purported to be of high genetic quality (i.e., high testosterone, masculinity, dominance, symmetry). The few significant preference shifts appeared to be research artifacts. The effects declined over time in published work, were limited to studies that used broader, less precise definitions of the fertile phase, and were found only in published research.

Bolds are mine.  As PZ Myers notes in his write-up of the study, the work that was not published may have been lower in quality.  But it may also have remained in the file drawers because it found a negative.  Research journals still favor new-and-shocking findings over no-effect findings.

Whether this meta-study gets it right or not, future studies, better done, could find such ovulation effects.  Though I personally doubt that.  Or rather, I doubt that any such effects would be large enough to matter when studied within the complicated context of human cultures.

The reference to "less precise definitions of the fertile phase" in that study abstract is also significant.  For example, if the fertile stage is defined widely enough, then those who want to see when women wear red or pink might be actually (and by accident) measuring women's desire not to wear red or pink when they are menstruating or close to that phase in their cycles.  The reasons for such avoidance (not saying it exists) are rather different from evolutionary explanations.

But what about the guys and ovulation?  Evolutionary psychology has something to say about that, too.  Remember the 2010 study which found that men could smell female ovulation by sniffing at women's sweaty t-shirts?   It was widely popularized, especially by John Tierney of the New York Times:

It may seem hard to believe that men could distinguish a woman who’s at peak fertility simply by sitting next to her for a few minutes. Scientists long assumed that ovulation in humans was concealed from both sexes.
But recent studies have found large changes in cues and behavior when a woman is at this stage of peak fertility. Lap dancers get much higher tips (unless they’re taking birth-control pills that suppress ovulation, in which case their tips remain lower). The pitch of a woman’s voice rises. Men rate her body odor as more attractive and respond with higher levels of testosterone.

It's that body odor stuff which comes from the 2010 study.  But a 2012 study didn't find any such testosterone effect.  That study wasn't an exact replication of the earlier one.  For example, it didn't prime the men by telling that they were going to smell the t-shirts worn by women and it didn't use shirts at all.  On the whole, it looks to me like a more carefully done study.  From the abstract:

Here, we collected axillary sweat samples from women on days near ovulation. In a crossover design, men who were not explicitly aware of the specific stimuli smelled the sweat samples in one session and water samples in a second session. There were no differences in testosterone responses across the experimental conditions.
 Now make a guess.  Did John Tierney write about that 2012 study or not? 

Sigh.  One reason I criticize the coverage of these kinds of studies is the easy pass they get from science pundits such as John Tierney (who has his own views on us wimminfolk).  Another reason is something I've spotted when I read through the articles.  Far too often the literature reviews in evolutionary psychology omit the critical studies, the studies which found nothing, the studies which were unclear.  That makes the edifice look formidably strong but writing the review that way is not ethical, in my humble opinion.  I hope to see this practice change in the future.

 *Thanks to Latverian Diplomat in the comments for the first three links.