(Medical Xpress)—Over the past two decades, studies in reproductive biology and psychology have purported to show a correlation between what women want in a male partner and their time of the month—demonstrating that which guy catches a woman's eye changes across the menstrual cycle.
But an independent analysis led by USC researchers of more than 58 experiments shows that this finding does not hold up. Despite prevailing theories of evolutionary biology and wide media coverage, there appear to be few significant shifts in what women want in a mate over the course of the menstrual cycle.
Fertile women may desire sex with men who seem particularly masculine or genetically fit—but no more so during peak fertility than in any other period of their cycles, reveals the meta-analysis of research led by Wendy Wood, USC Provost Professor of Psychology and Business, and vice dean for social sciences at USC Dornsife. Similarly, when women are not as fertile—sharing certain hormonal profiles with pregnancy—they are not especially oriented toward kinder, gentler mates who can provide for their young.
The thorough review of research on the drivers of human reproduction, in the journal Emotion Review, highlights the importance of verification in the scientific method, as well as potential problems in how science is reported in the media. Wood and her team found that the correlations between menstrual cycle and mate preference declined over time. That is, most subsequent attempts to replicate the findings showed less of an effect. They also reveal that papers that did not show a link between menstrual cycle and sexual preference—that only showed no such correlation existed—were much less likely to be accepted for publication in a journal, often despite more precise methodology.
"These effects have become accepted lore," said Wood, who has a joint appointment at USC Marshall School of Business. "Our failure to find consistent effects of women's hormonal cycling on mate preferences does not, of course, rule out such influences. Yet our review suggests these effects are subtle, if at all present.
"By relying on outmoded theories that emphasize biology to the exclusion of culture, evolutionary psychologists may be missing some of the most important, characteristically human processes—our remarkable ability to exert control over our own behavior."
The USC Dornsife team systematically analyzed prior research, which has used a range of factors to indicate male genetic fitness in experiments including: size of jaw, cheekbone and brow ridges; facial hair; lower voice pitch; dominant behavior conveying power and leadership; symmetry; and sweat odor. Other studies examined women's preferences for partners with relationship skills during less fertile periods.
They then looked at how scientists determined fertility, including assessments of reproductive hormone levels and self-reported menstruation cycles, and compared whether fertile (as opposed to non-fertile) women found genetically fit men sexier.
The results of the meta-analysis showed that fertile and non-fertile women preferred men with masculine attributes who demonstrated dominant behavior. More importantly, the preference for manly males wasn't any stronger among women who were in the fertile phase of their menstrual cycle. And wherever they were on their menstrual cycles, women also preferred kind men, the researchers found, and these preferences held across both long-term and short-term relationships.
"A complete model of human reproduction needs to acknowledge women's impressive capacity to regulate their own behavior and not fall into the trap of biological determinism," said Wood, one of the world's leading experts on self-control and regulation. Wood's past research has played a key role in expanding our understanding of habits, as well as gender differences in social behavior.
"Regardless of what might have been normative in ancestral history, with the advent of cultural roles and complex group living, women showed the capacity to tailor their reproductive activities to a variety of social roles," Wood says.
Laura Kressel, Priyanka D. Joshi and Brian Louie of USC were co-authors of the study. Wendy Wood was supported by a fellowship from the Radcliffe Institute for Advanced Study during initial stages of this work.