Women who settle down with a stable guy instead of a sexy one might subconsciously struggle with that decision during their most fertile window of the month, a new study suggests.
Just before ovulating, women with a more reliable long-term partner are more likely to have negative feelings about their beau than those paired with more sexually desirable men, the researchers found.
"A woman evaluates her relationship differently at different times in her cycle, and her evaluation seems to be colored by how sexually attractive she perceives her partner to be," researcher Martie Haselton, a professor of psychology and communication studies at UCLA, said in a statement.
For the study, Haselton and UCLA doctoral student Christina Larson recruited 41 undergraduate women in long-term heterosexual relationships and tracked their menstrual cycles. The researchers also asked the participants questions about their partners aimed at determining how stable and sexually attractive the guys might be. For example, they asked, "How desirable do you think women find your partner as a short-term mate or casual sex partner, compared to most men?" Then at a high-fertility point (just before ovulation) and low-fertility point, the women were then asked about the quality of their relationship.
Overall, the participants' commitment to and satisfaction with their relationships did not seem to change with fertility, the researchers found. But women with less sexually attractive partners seemed to feel less close to their beaus as they moved from their least fertile to most fertile period. Meanwhile, women matched with the most sexually attractive men seemed to experience the opposite effect.
"Women with the really good, stable guy felt more distant at high-fertility periods than low-fertility periods," Haselton explained in a statement. "That isn't the case with women who were mated to particularly sexually attractive men. The closeness of their relationships got a boost just prior to ovulation."
The researchers found the same trends when they repeated the experiment with 67 new participants. In this phase of the study, the researchers added a new questionnaire that had the women rate their partners' flaws, such as thoughtlessness, moodiness and childishness. Women paired with less sexually attractive guys were significantly more likely to find fault with their partners during the high-fertility period than the low-fertility period. [10 Odd Facts About the Female Body]
The sometimes conflicting desires for stability and sexiness in a partner could come from mating strategies designed to benefit our female ancestors a long time ago, the researchers said.
"Since our female ancestors couldn't directly examine a potential partner's genetic makeup, they had to base their decisions on physical manifestations of the presence of good genes and the absence of genetic mutations, which might include masculine features such as a deep voice, masculine face, dominant behavior and sexy looks," Haselton explained.
But genes aren't everything.
"In the reproductive arena, women probably evolved to desire men who could contribute both quality care and good genes," Haselton said. "The problem is that there is a limited number of potential mates who are high in both. So many women are forced to make trade-offs."
The researchers say "Mr. Stable" need not worry too much as the apparent negative feelings during ovulation don't seem to affect long-term commitment.
"Even when these women are feeling less positive about their relationship, they don't want to end it," Larson said in a statement. But the team is interested in whether the changes in behavior are apparent to guys.
"We don't know if men are picking up on this behavior, but if they are, it must be confusing for them," Larson said.
The study — which will be detailed in the November issue of the journal Hormones and Behavior — is the latest of many that have found a woman's fertile phase can cause subtle changes in her behavior. One suggested that ovulating women have more sexual fantasies, and another found they are more likely to prefer masculine guys when most fertile. A 2011 study even suggested that women are more likely to see Georgia O'Keeffe paintings as erotic during this fertile window. Oh yeah, and fertile gals spot snakes faster than women at other times of the menstrual cycle.
Sign up for the Live Science daily newsletter now
Get the world’s most fascinating discoveries delivered straight to your inbox.