Menstrual cycle phase alters women's sexual preferences for composers of more complex music

Over 140 years ago Charles Darwin first argued that birdsong and human music, having no clear survival benefit, were obvious candidates for sexual selection. Whereas the first contention is now universally accepted, his theory that music is a product of sexual selection through mate choice has largely been neglected. Here, I provide the first, to my knowledge, empirical support for the sexual selection hypothesis of music evolution by showing that women have sexual preferences during peak conception times for men that are able to create more complex music. Two-alternative forced-choice experiments revealed that woman only preferred composers of more complex music as short-term sexual partners when conception risk was highest. No preferences were displayed when women chose which composer they would prefer as a long-term partner in a committed relationship, and control experiments failed to reveal an effect of conception risk on women''s preferences for visual artists. These results suggest that women may acquire genetic benefits for offspring by selecting musicians able to create more complex music as sexual partners, and provide compelling support for Darwin''s assertion ‘that musical notes and rhythm were first acquired by the male or female progenitors of mankind for the sake of charming the opposite sex’.     

Menstrual cycle: Effect on sweetness preferences in women

Variations in how pleasant sugar solutions are, as rated by women, occur at different stages of the menstrual cycle. Following a glucose meal sweet solutions become less pleasant, but this shift is slower at the time of ovulation. The significance of these changes is discussed.     

Do women's preferences for symmetry change across the menstrual cycle?

In many species, symmetry enhances physical attractiveness of the face and body. In humans, facial attractiveness is also enhanced by symmetrical decoration in the form of facial paint [Cárdenas, R. A., & Harris, L. J. (2006)]. According to the good-genes hypothesis [e.g., Thornhill, R., & Gangestad, S. W. (1999)], symmetry is preferred because it is associated with mate quality. According to the receiver bias hypothesis [e.g., Enquist, M., & Johnstone, R. (1997)], it is a by-product of how the visual system is designed. Proponents of the good-genes hypothesis have suggested that a preference for symmetry may vary with fertility, namely, that it will be enhanced in women in the high-fertility phase of the menstrual cycle. Previous research does demonstrate that, during this phase, women prefer the scent of more symmetrical men [e.g., Gangestad, S. W., & Thornhill, R. (1998)]. However, research employing assessment of faces fails to find a similar effect [Koehler, N., Rhodes, G., & Simmons, L. W. (2002)]. Previous research asked subjects to judge faces one at a time during high fertility (around ovulation) and low fertility (menstruation). We used a different face-presentation method, tested women during the other low-fertility (midluteal) phase, and used decorated as well as undecorated faces. As in our prior study [Cárdenas, R. A., & Harris, L. J. (2006)], symmetry of facial features and symmetry of decoration enhanced attractiveness, but, contrary to the possible prediction of the good-genes hypothesis, the effects did not vary across the cycle. The results as they are, therefore, can be equally accommodated by both hypotheses.     

Menstrual cycle, trait estrogen level, and masculinity preferences in the human voice

Men with low testosterone (feminine men) invest in relationships and offspring more than men with high testosterone (masculine men). Women's attraction to testosterone dependent traits (e.g. masculine face shape) is enhanced during the late-follicular, fertile phase of the menstrual cycle. Attractive, feminine women have stronger preferences for masculine men as possible long-term partners than less attractive, masculine women. We manipulated 2 testosterone related vocal traits (voice pitch and apparent vocal-tract length) in voices to test if women prefer masculinized men's voices to feminized men's voices; masculinity preferences are enhanced at the fertile (late-follicular) menstrual cycle phase; the amount that masculinity preferences shift cyclically relates to average estrone-3-glucuronide concentration (the primary urinary metabolite of estrone, E3G). We found women displayed general masculinity preferences for men's voices; masculinity preferences were greater in the fertile (late-follicular) phase of the cycle than the non-fertile (early-follicular and luteal) phase; and this effect was most pronounced for women with low average E3G concentration. As feminine women (i.e. those with high average E3G levels) are most able to obtain investment even from masculine men, these women may not need to change their mating preference or strategy during the menstrual cycle as much as masculine women.     

The health of a nation predicts their mate preferences: cross-cultural variation in women's preferences for masculinized male faces

Recent formulations of sexual selection theory emphasize how mate choice can be affected by environmental factors, such as predation risk and resource quality. Women vary greatly in the extent to which they prefer male masculinity and this variation is hypothesized to reflect differences in how women resolve the trade-off between the costs (e.g. low investment) and benefits (e.g. healthy offspring) associated with choosing a masculine partner. A strong prediction of this trade-off theory is that women''s masculinity preferences will be stronger in cultures where poor health is particularly harmful to survival. We investigated the relationship between women''s preferences for male facial masculinity and a health index derived from World Health Organization statistics for mortality rates, life expectancies and the impact of communicable disease. Across 30 countries, masculinity preference increased as health decreased. This relationship was independent of cross-cultural differences in wealth or women''s mating strategies. These findings show non-arbitrary cross-cultural differences in facial attractiveness judgements and demonstrate the use of trade-off theory for investigating cross-cultural variation in women''s mate preferences.     

Menstrual cycle variation in spatial ability: relation to salivary cortisol levels

This study examined whether menstrual cycle phase was associated with performance on the Primary Mental Abilities Test of Spatial Relations, a test of mental rotation, in undergraduate students (N = 82). As cortisol levels also vary across the menstrual cycle under conditions of stress and influence cognitive performance, saliva samples were obtained before and after the test session to examine whether cortisol levels were related to between- and within-group differences in spatial performance. Men scored higher on the spatial test than all the groups of women, although the difference between men and women in the menstrual phase was not significant. Women in the luteal phase scored lower than the menstrual, follicular, and oral contraceptive user groups of women. There were no sex or menstrual cycle differences in cortisol levels, and no association between cortisol levels and spatial performance. The poorer performance of women in the luteal phase was not related to differences in ratings of perceived stress, perceived success on the test, or mood. Although menstrual cycle phase accounted for a significant proportion of the variance (15%) in performance on the spatial test, this does not explain why men outperformed women regardless of the phase of the cycle. Thus, there are clearly several other variables, sociocultural and physiological, involved in mediating individual differences in spatial performance.     

Hormones and social monitoring: Menstrual cycle shifts in progesterone underlie women's sensitivity to social information

During the luteal phase of the menstrual cycle, women's bodies prepare themselves for possible pregnancy and this preparation includes a dramatic increase in progesterone. This increase in progesterone may underlie a variety of functionally relevant psychological changes designed to help women overcome challenges historically encountered during pregnancy (e.g., warding off social threats and recruiting allies). This paper reports data supporting the hypothesis that increases in progesterone during the luteal phase underlie heightened levels of social monitoring—that is, heightened sensitivity to social cues indicating the presence of social opportunity or threat. Increases in progesterone during the luteal phase were associated with increased accuracy in decoding facial expressions (Study 1) and increased attention to social stimuli (Study 2). Findings suggest that increases in progesterone during the luteal phase may be linked functionally with low-level perceptual attunements that help women effectively navigate their social world.     

Menstrual cycle shifts in attentional bias for courtship language

The current study investigated whether women show an attentional bias toward courtship language during the fertile phase of their menstrual cycle. Thirty heterosexual women (17 naturally cycling, 13 using hormonal contraceptives) completed a dichotic listening task on both a high and low fertility day of their menstrual cycle. Participants were asked to verbally repeat (shadow) an emotionally neutral target passage played in one ear while either a neutral or courtship distracter was played in the other ear. Courtship distracters were flirtatious in content but not overtly sexual. Shadowing errors were coded as a measure of attentional bias toward the distracter. Saliva samples were taken to determine whether levels of estradiol, progesterone and/or testosterone correlated with task performance. As predicted, naturally cycling women made more shadowing errors when listening to a courtship distracter during the fertile phase of their cycle than during the nonfertile phase. This effect was moderated by relationship status, such that fertile, mated women showed an attentional bias for courtship language but fertile single women did not. However, because of small sample sizes in the analysis, this relationship should be viewed as preliminary. Hormonal analysis revealed that higher levels of salivary estradiol predicted greater attentional bias toward courtship language in naturally cycling women. These results suggest that women's attention is drawn to verbal courtship signals when they are fertile, and that this shift is linked to increased estradiol release during the periovulatory phase.     

Menstrual variation in salivary testosterone among regularly cycling women.

To determine menstrual variation in salivary testosterone daily saliva samples were collected from 20 regularly cycling women. Results indicate that the menstrual profile of salivary testosterone for both ovulatory and anovulatory cycles exhibits local peaks during the follicular phase and at midcycle, as well as a luteal trough. However, the testosterone profile for anovulatory cycles exhibited a later midcycle peak than that for ovulatory cycles, as well as significantly higher average testosterone levels. These results extend the observation of a midcycle peak in serum testosterone to saliva and suggest the existence of a follicular peak in unbound testosterone coincident with the early androgen production of a cohort of developing follicles.     

Menstrual cycle exhibits no effect on postprandial lipemia.

Menstrual cycle effects on postprandial lipemia were investigated in 13 healthy women. They were monitored (dietary intake, basal body temperature) for a period of one cycle. Statistically significant follicular-luteal differences were neither observed between fasting triglyceride serum levels nor between areas under triglyceride response curves after a standardized oral fat load.     

Menstrual cycle phase affects temperature regulation during endurance exercise.

We investigated whether menstrual cycle phase would affect temperature regulation during an endurance exercise bout performed at room temperature (Ta) of 22 degrees C and 60% relative humidity. Nine eumenorrheic women [age 27.2 +/- 3.7 yr, peak O2 uptake (VO2) 2.52 +/- 0.35 l/min] performed 60 min of cycle exercise at 65% of peak VO2. Subjects were tested in both midfollicular (F) and midluteal (L) phases, although one woman did not show a rise in serum progesterone (P4) that is typically evident 1 wk after ovulation. VO2, rectal (Tre) and skin (Tsk) temperatures, heart rates (HR), and ratings of perceived exertion (RPE) were measured throughout exercise. Sweat loss (SL) was estimated from pre- and postexercise body weight differences. VO2, SL, and Tsk were not affected by menstrual cycle phase. Preexercise Tre was 0.3 degrees C higher during L than during F conditions, and this difference increased to 0.6 degrees C by the end of exercise (P less than 0.01). Compared with F, HRs during L were approximately 10 beats/min greater (P less than 0.001) at all times, whereas RPE responses were significantly greater (P less than 0.01) by 50 min of cycling. No differences in any measured values were found in the subject whose P4 was low in both test conditions. Results indicate that thermoregulation (specifically, regulation of Tre), as well as cardiovascular strain and perception of exercise, was adversely affected during the L phase.     

Changes in salivary estradiol predict changes in women's preferences for vocal masculinity

Although many studies have reported that women's preferences for masculine physical characteristics in men change systematically during the menstrual cycle, the hormonal mechanisms underpinning these changes are currently poorly understood. Previous studies investigating the relationships between measured hormone levels and women's masculinity preferences tested only judgments of men's facial attractiveness. Results of these studies suggested that preferences for masculine characteristics in men's faces were related to either women's estradiol or testosterone levels. To investigate the hormonal correlates of within-woman variation in masculinity preferences further, here we measured 62 women's salivary estradiol, progesterone, and testosterone levels and their preferences for masculine characteristics in men's voices in five weekly test sessions. Multilevel modeling of these data showed that changes in salivary estradiol were the best predictor of changes in women's preferences for vocal masculinity. These results complement other recent research implicating estradiol in women's mate preferences, attention to courtship signals, sexual motivation, and sexual strategies, and are the first to link women's voice preferences directly to measured hormone levels.     

Eugenol synthase genes in floral scent variation in Gymnadenia species

Floral signaling, especially through floral scent, is often highly complex, and little is known about the molecular mechanisms and evolutionary causes of this complexity. In this study, we focused on the evolution of “floral scent genes” and the associated changes in their functions in three closely related orchid species of the genus Gymnadenia. We developed a benchmark repertoire of 2,571 expressed sequence tags (ESTs) in Gymnadenia odoratissima. For the functional characterization and evolutionary analysis, we focused on eugenol synthase, as eugenol is a widespread and important scent compound. We obtained complete coding complementary DNAs (cDNAs) of two copies of putative eugenol synthase genes in each of the three species. The proteins encoded by these cDNAs were characterized by expression and testing for activity in Escherichia coli. While G. odoratissima and Gymnadenia conopsea enzymes were found to catalyze the formation of eugenol only, the Gymnadenia densiflora proteins synthesize eugenol, as well as a smaller amount of isoeugenol. Finally, we showed that the eugenol and isoeugenol producing gene copies of G. densiflora are evolutionarily derived from the ancestral genes of the other species producing only eugenol. The evolutionary switch from production of one to two compounds evolved under relaxed purifying selection. In conclusion, our study shows the molecular bases of eugenol and isoeugenol production and suggests that an evolutionary transition in a single gene can lead to an increased complexity in floral scent emitted by plants.     

Menstrual cycle phase affects discrimination of infant cuteness

Recent studies have shown that women are more sensitive than men to subtle cuteness differences in infant faces. It has been suggested that raised levels in estradiol and progesterone may be responsible for this advantage. We compared young women's sensitivity to computer-manipulated baby faces varying in cuteness. Thirty-six women were tested once during ovulation and once during the luteal phase of their menstrual cycle. In a two alternative forced-choice experiment, participants chose the baby which they thought was cuter (Task 1), younger (Task 2), or the baby that they would prefer to babysit (Task 3). Saliva samples to assess levels of estradiol, progesterone and testosterone were collected at each test session. During ovulation, women were more likely to choose the cuter baby than during the luteal phase, in all three tasks. These results suggest that cuteness discrimination may be driven by cyclic hormonal shifts. However none of the measured hormones were related to increased cuteness sensitivity. We speculate that other hormones than the ones measured here might be responsible for the increased sensitivity to subtle cuteness differences during ovulation.     

Menstrual cycle characteristics of seasonally breeding rhesus monkeys

Rhesus monkeys in seminatural environments exhibit a distinct seasonal mating cycle with conceptions restricted to the fall and winter months. In the present study, the characteristics of menstrual cycles were examined during a 1-year period in twelve rhesus monkeys in whom pregnancy was prevented. Menses occurred throughout the year, but ovulations were observed only in the fall and winter months. Menses in the spring and summer months occurred irregularly and were associated exclusively with anovulatory cycles. The total number of ovulations exhibited by these females during the breeding season ranged from two to six and was positively related to body weight, mean luteal phase progesterone (P) levels of normal cycles and social dominance rank. Ovulations with a short luteal phase were exhibited by four females (seven cycles), with the likelihood of occurrence increasing as the breeding season progressed. The incidence of abnormal cycles was predicted from the linear combination of parity, body weight and luteal phase P of normal ovulatory cycles. These results suggest that during the seasonally delimited period of ovulation, females exhibit a range in the quality and quantity of ovulations which may be predicted by certain idiosyncratic physical and behavioral traits.     

Olfactory preferences, scent marking, and "proceptivity" in female hamsters

Two appetitive sexual behaviors of female hamsters, attraction to odors of males and vaginal scent marking, were investigated and the correlations of each to reproductive states were determined. Both estrous and diestrous females were more attracted to the odors of intact males than to the odors of females or castrated males; this differential attraction was more pronounced for estrous females. Lactating females, but not pregnant females, were also preferentially attracted to odors of intact males. Thus, odors alone provided sufficient information to allow sexual discrimination by females, and estrous, diestrous, and lactating females were preferentially attracted to odors of intact males whereas pregnant females were not. Reproductive condition had no influence on responses to odors of castrated males or diestrous females. Vaginal scent marking was strongly influenced by reproductive state: Marking frequency was low in estrous, pregnant, and early lactation females, but high in late lactation and diestrous females, suggesting a function of advertisement of approaching receptivity. Thus sexual preferences based on olfactory cues and vaginal scent-marking frequency differed in their relationships to reproductive conditions. It is suggested that in other species such relationships between appetitive sexual behaviors and reproductive condition will depend on the species social organization, ecological niche, and taxonomic group, and consequently that the concept of preceptive behaviors should be broadened to include all appetitive sexual behaviors of females, not just those that are correlated with the hormonal state characterizing estrus.