Ovulatory shift hypothesis

Two meta-analyses published in 2014 reached opposing conclusions on whether the existing evidence was robust enough to support the prediction that women's mate preferences change across the cycle.

[3][4] A newer 2018 review does not show women changing the type of men they desire at different times in their fertility cycle.

[7] The hypothesis separately proposes that hormonal changes across the cycle cause women, when they are most likely to get pregnant, to be more attracted to traits in potential short-term male sexual partners that indicate high genetic quality, leading to greater reproductive success.

[12][page needed][13][page needed] However, research has shown that human females may in fact experience subtle but distinct physiological, behavioral, and cognitive changes during the high-fertility phase of their ovulatory cycle,[2][3] and that both men and other women can detect signals that indicate high-fertility in a woman,[14] which may indicate that humans have retained an estrus-like state.

Some researchers have suggested that over evolutionary time, women may have maximized reproductive success by seeking good genes from an extra-pair copulation—cheating on their partner—at high fertility, while also maintaining a long-term pair bond with a partner who provides parenting resources for the offspring, sometimes called the dual strategy hypothesis.

[21][13][page needed] Of course, an optimal partner is one with both sexy cad and good dad traits, but such a man is statistically unlikely to be common.

[25] Numerous studies have demonstrated ovulatory cycle shifts in women's mating-related motivations, preferences, thoughts, and behaviors.

While some studies have found increases in frequency of sexual activity at high fertility,[29][30][31] larger studies have concluded that there is generally no difference in frequency of sexual activity across the ovulatory cycle,[32] possibly due to the multitude of factors that affect the ability to engage in sex (e.g., access to a partner, partner's desire, time for engaging, etc.).

[37] The ovulatory shift hypothesis proposes that women at high fertility should be most attracted to short-term sexual partners with physical and behavioral features that likely signal genetic fitness, or good genes.

Having symmetrical features may indicate that an individual possesses high-quality genes related to health, and that they developed in a stable environment with little disease or trauma.

[38] Studies have found that women rate faces of more symmetrical men as more attractive during high fertility, especially when evaluating them as short-term partners.

[1][40] Although many studies and one meta-analysis have shown that fertility-moderated shifts in attraction to facial and bodily symmetry occur robustly,[3] other reviews have concluded that the effect is small or non-existent.

[46] While many studies have shown that women tend to be attracted to more masculine characteristics at high fertility,[47] results have been mixed,[48] and two meta-analyses have concluded that the effect is not robust.

The ovulatory shift hypothesis proposes that women's behavior during the fertile phase should also reflect evolutionary adaptations for reproductive success.

Fertile-phase women also spend more time on their appearance and tend to wear accessories like jewelry, makeup, or hairstyles that are perceived as trying to look more attractive.

[58][59] Additionally, several studies have demonstrated that women tend to purchase more products related to enhancing their appearance, attractive clothing, shoes, or accessories, during the fertile window.

[60][59] One of the earliest studies on ovulatory shifts found that female lab rats tend to run on their exercise wheels more during their fertile window.

[61][page needed] Subsequent research showed that a variety of species experience an increase in the frequency of spontaneous activity and motor behavior during estrus.

[62][63] Some studies on humans have shown a similar pattern: women walk more steps, as counted by a pedometer, during the high-fertility phase of their cycle.

[69][page needed] The sex that invests more in offspring should be more intersexually selective, or picky when choosing a sexual partner, because they have more time and resources to lose if they make a poor choice.

[35][37] One study found that after interacting with their partner during the fertile phase, men shown a photograph of an attractive man exhibit increased testosterone, which may be a competitive response.

[15] One meta-analysis and a review of the literature have been conducted on both published and unpublished data that support the claim of the ovulatory shift hypothesis that women experience changes in attraction preferences at high fertility.

[3][20] However, another meta-analysis and subsequent commentary concluded that the effect is not actually significant and may be a result of some studies using imprecise measurements of when women are in the fertile window, as well as publication bias.

[4] A review subsequently published also does not show women changing the type of men they desire at different times in their fertility cycle.