Urszula M. Marcinkowska

The role of sexual imprinting and the Westermarck effect in mate choice in humans

Positive sexual imprinting is a process by which individuals use the phenotype of their opposite-sex parent as a template for choosing mates and is suggested to play an important role in human mate choice. In contrast, negative imprinting, or “The Westermarck Effect”, is characterized by individuals developing a strong sexual aversion to others with whom they lived closely in infancy and early childhood. In this review, we evaluate the literature on their effects on mate choice in humans. We find little evidence to support positive imprinting in humans because the studies either have serious design flaws, do not exclude effects of heritable mating preferences, or do not account for several possible alternative explanations. Instead, it seems that the opposite phenomenon, negative sexual imprinting, has some support from natural experiments which have found that individuals avoid mating with those with whom they lived closely in infancy and early childhood. However, it seems that early association does not produce a strong-enough aversion to completely annihilate sexual desire, probably because the mind uses multiple kinship cues to regulate inbreeding avoidance. Thus, it appears that the evidence for both types of imprinting is fairly weak in humans. Thus, more studies are needed to test the role of sexual imprinting on mate choice in humans, especially those measuring interactions between positive and negative imprinting.

Cross cultural variation in men's preference for sexual dimorphism in women's faces

Both attractiveness judgements and mate preferences vary considerably cross-culturally. We investigated whether mens preference for femininity in womens faces varies between 28 countries with diverse health conditions by analysing responses of 1972 heterosexual participants. Although men in all countries preferred feminized over masculinized female faces, we found substantial differences between countries in the magnitude of mens preferences. Using an average femininity preference for each country, we found mens facial femininity preferences correlated positively with the health of the nation, which explained 50.4% of the variation among countries. The weakest preferences for femininity were found in Nepal and strongest in Japan. As high femininity in women is associated with lower success in competition for resources and lower dominance, it is possible that in harsher environments, men prefer cues to resource holding potential over high fecundity.

Cross-cultural variation in women's preferences for cues to sex- and stress-hormones in the male face

Women in the UK prefer the faces of men with low levels of the stress hormone cortisol, and the relationship is moderated by the sex hormone testosterone. In a Latvian sample, however, womens preferences were not affected by cortisol, and the interaction with testosterone differed from that of the UK. To further explore cross-cultural variation in preferences for facial cues to sex- and stress-hormones, we tested the preferences of women from 13 countries for facial composites constructed to differ in combinations of the hormones. We found significant relationships between a measure of societal development (the United Nations human development index 2011) and preferences for cues to testosterone in the face, and the interaction between preferences for cues to testosterone and cortisol. We also found a significant relationship between preferences for cues to testosterone and a societal-level measure of parasite stress. We conclude that societal-level ecological factors influence the relative value of traits revealed by combinations of sex- and stress-hormones.

Sexual Imprinting on Facial Traits of Opposite-Sex Parents in Humans

Positive sexual imprinting is a process by which individuals use the phenotype of their opposite-sex parent as a template for acquiring mates. Recent studies in humans have concluded that an imprinting-like mechanism influences human mate choice in facial traits. However, some of the previous studies have had methodological problems or flaws which might have invalidated or led to an overgeneralization of the original interpretation of their results. In this study, 70 heterosexual adults were used to test if their partners resembled facially their opposite-sex parent as the sexual imprinting hypothesis predicts. Judges assessed the subjective facial similarity between each participants partner and their parent. We found that there was no perceived facial similarity between womens partners and their fathers. However, men tended to pair more often with women that were perceived as resembling the mens own mothers. In contrast to previous studies, the quality of the relationship between participants and their parents did not predict the level of facial resemblance between the participants spouse and their parent.

Lack of support for relation between woman's masculinity preference, estradiol level and mating context.

It has been proposed that womens preferences for male facial sexual dimorphism are positively correlated with conception probability and differ between short- and long-term mating contexts. In this study, we tested this assumption by analyzing relationships between estradiol levels to the womens preferences of male faces that were manipulated to vary in masculinity. Estradiol was measured in daily saliva samples throughout the entire menstrual cycle collected by Polish women with regular menstrual cycles. In our analyses, we included the three most commonly used definitions of the fertile window in the literature. After computing the overall masculinity preference of each participant and measuring hormone levels, we found that i) the timing of ovulation varied greatly among women (between -11 and -17days from the onset of the next menses, counting backwards), ii) there was no relationship between daily, measured during the day of the test (N=83) or average for the cycle (N=115) estradiol levels and masculinity preferences, iii) there were no differences in masculinity preferences between women in low- and high-conception probability phases of the cycle, and iv) there were no differences in masculinity preferences between short- and long-term mating contexts. Our results do not support the idea that womens preferences for a potential sexual partners facial masculinity fluctuate throughout the cycle.

Gaze Properties of Women Judging the Attractiveness of Masculine and Feminine Male Faces

Most studies of female facial masculinity preference have relied upon self-reported preference, with participants selecting or rating the attractiveness of faces that differ in masculinity. However, researchers have not established a consensus as to whether womens general preference is for male faces that are masculine or feminine, and several studies have indicated that women prefer neither. We investigated womens preferences for male facial masculinity using standard two-alternative forced choice (2AFC) preference trials, paired with eye tracking measures, to determine whether conscious and non-conscious measures of preference yield similar results. We found that women expressed a preference for, gazed longer at, and fixated more frequently on feminized male faces. We also found effects of relationship status, relationship context (whether faced are judged for attractiveness as a long- or short-term partner), and hormonal contraceptive use. These results support previous findings that women express a preference for feminized over masculinized male faces, demonstrate that non-conscious measures of preference for this trait echo consciously expressed preferences, and suggest that certain aspects of the preference decision-making process may be better captured by eye tracking than by 2AFC preference trials.

Men’s Preferences for Female Facial Femininity Decline With Age

OBJECTIVES Women tend to have a smaller chin, fuller lips, and rounder eyes than men, due in part to the effects of estrogen. These features associated with facial femininity have been found to be positively associated with fertility. Although young men in their 20s typically judge facial femininity as more attractive than facial masculinity, at all ages, men with higher sexual desire and testosterone levels tend to show a marked preference for feminine faces. In the current study, we extend this research using a large cross-national sample to test the hypothesis that facial femininity preferences will be stronger among younger men than among older men. We also tested whether these preferences are influenced by self-reported sexual openness, national health indices, and gross national income. METHOD We quantified attractiveness judgments (i.e., preferences) among 2,125 heterosexual men (aged 17-73 years) for female faces that were manipulated to appear more or less feminine using a computer graphics program. RESULTS Facial femininity preferences decreased with age, being highest among men in their 30s and lowest among men in their 70s. This pattern was independent of mens sexual openness and cross-national variation in health and socioeconomic development. DISCUSSION Our study shows that mens preferences for facial femininity are age dependent. At the proximate level, differences in preferences could reflect age-related declines in testosterone levels. These age-related declines in preferences could benefit older men, who are less able to invest in mating effort, and thus may opt out of competition with younger men for mates with potentially higher fertility.

Women's preferences for men's beards show no relation to their ovarian cycle phase and sex hormone levels

ABSTRACT According to the ovulatory shift hypothesis, womens mate preferences for male morphology indicative of competitive ability, social dominance, and/or underlying health are strongest at the peri‐ovulatory phase of the menstrual cycle. However, recent meta‐analyses are divided on the robustness of such effects and the validity of the often‐used indirect estimates of fertility and ovulation has been called into question in methodological studies. In the current study, we test whether womens preferences for mens beardedness, a cue of male sexual maturity, androgenic development and social dominance, are stronger at the peri‐ovulatory phase of the menstrual cycle compared to during the early follicular or the luteal phase. We also tested whether levels of estradiol, progesterone, and the estradiol to progesterone ratio at each phase were associated with facial hair preferences. Fifty‐two heterosexual women completed a two‐alternative forced choice preference test for clean‐shaven and bearded male faces during the follicular, peri‐ovulatory (validated by the surge in luteinizing hormone or the drop in estradiol levels) and luteal phases. Participants also provided for one entire menstrual cycle daily saliva samples for subsequent assaying of estradiol and progesterone. Results showed an overall preference for bearded over clean‐shaven faces at each phase of the menstrual cycle. However, preferences for facial hair were not significantly different over the phases of menstrual cycle and were not significantly associated with levels of reproductive hormones. We conclude that womens preferences for mens beardedness may not be related to changes in their likelihood of conception. HighlightsThe first study testing whether hormonal variation among women is associated with preferences for mens beardednessResults showed that preferences did not change over the menstrual cycle.Preferences were also unrelated to changes in estradiol and progesterone over the menstrual cycle.Our results suggest that womens preferences for mens beardedness may not change with fecundability.

Digit ratio (2D:4D) and circulating testosterone, oestradiol, and progesterone levels across the menstrual cycle

BACKGROUND Digit ratio (2D:4D) is used by researchers as an indicator of prenatal sex hormone exposure. Two previous studies have examined associations between 2D:4D and circulating sex steroid concentrations across the menstrual cycle in adult females. One reported that digit ratio correlated positively with oestradiol levels, whereas the other found no such effect; neither observed significant associations with progesterone. AIMS To examine associations between 2D:4D, as well as asymmetry (i.e. right minus left 2D:4D), and circulating sex steroids across the menstrual cycle. STUDY DESIGN Correlational. SUBJECTS 32 naturally cycling adult females from rural southern Poland. OUTCOME MEASURES Salivary oestradiol, progesterone, testosterone, and testosterone to oestradiol ratio (T:O) measured during the follicular, peri-ovulatory, and luteal phases. Average levels across the cycle were also examined. RESULTS AND CONCLUSIONS Asymmetry in digit ratio correlated positively with oestradiol at each phase, as well as with average levels across the cycle. Each association, other than that relating to average levels, remained statistically significant after a range of covariates had been controlled for. No other significant correlations were observed between digit ratio variables and circulating hormone levels. Our results might suggest that low exposure to androgens and/or high exposure to oestrogens during gestation is a predictor of high oestradiol levels in naturally cycling females of reproductive age. However, considering that it was asymmetry in digit ratio, and not either right or left 2D:4D, that was a significant predictor, it is also possible that these effects reflect more general associations between bilateral asymmetry and circulating oestradiol levels.

Value of digit ratio 2D:4D, a biomarker of prenatal hormone exposure, is stable across the menstrual cycle

Digit ratio (2D:4D) is used as a marker of prenatal hormone exposure and, consequently, as a predictor of many characteristics throughout a womans lifespan. A previous study has suggested that values of 2D:4D vary across menstrual cycles and further questioned the reliability of a single measurement of 2D:4D among cycling women, while another study failed to confirm these results. However, these studies estimated the timing of cycle phases based on a date of menstruation reported by participants and also had small sample sizes. For our study, we evaluated potential changes in 2D:4D values across a menstrual cycle in a group of women among whom the phases of the menstrual cycle were determined by hormonal (luteinizing hormone based) ovulation tests. We studied 32 naturally cycling women aged 22-37 from rural Poland. Lengths of second and fourth digits were measured based on scans of both hands taken three times (i.e. in the follicular phase, peri-ovulatory phase and luteal phase of the cycle) for each participant. No differences in 2D:4D value across the menstrual cycle were detected either when right-hand, left-hand, and mean 2D:4D for both hands were analysed, nor when difference in the 2D:4D value between hands (Dleft-right) was evaluated. We documented that 2D:4D is independent of the phase of the menstrual cycle and these findings suggest that among naturally cycling women, a value of 2D:4D can be reliably obtained from measurements taken during any day of the menstrual cycle.