Age Effects on Women's and Men's Dyadic and Solitary Sexual Desire.

While most studies on sexuality in later life report that sexual desire declines with age, little is known about the exact nature of age effects on sexual desire. Using self-reported dyadic sexual desire relating to a partner, dyadic sexual desire relating to an attractive person, and solitary sexual desire from a large (N > 8000) and age diverse (14.6-80.2 years) online sample, the current study had three goals: First, we investigated relationships between men and women's sexual desire and age. Second, we examined whether individual differences such as gender/sex, sexual orientation, self-rated masculinity, relationship status, self-rated attractiveness, and self-rated health predict sexual desire. Third, we examined how these associations differed across sexual desire facets. On average, the associations between age and both men and women's sexual desire followed nonlinear trends and differed between genders/sexes and types of sexual desire. Average levels of all types of sexual desire were generally higher in men. Dyadic sexual desire related positively to self-rated masculinity and having a romantic partner and solitary desire was higher in people with same-sex attraction. We discuss the results in the context of the evolutionary hypothesis that predict an increase of sexual desire and female reproductive effort prior to declining fertility. Our findings both support and challenge beliefs about gender/sex specificity of age effects on sexual desire and highlight the importance of differentiating between desire types.

Preregistered Direct Replication of "Sick Body, Vigilant Mind: The Biological Immune System Activates the Behavioral Immune System".

The tendency to attend to and avoid cues to pathogens varies across individuals and contexts. Researchers have proposed that this variation is partially driven by immunological vulnerability to infection, though support for this hypothesis is equivocal. One key piece of evidence (Miller & Maner, 2011) shows that participants who have recently been ill-and hence may have a reduced ability to combat subsequent infection-allocate more attention to faces with infectious-disease cues than do participants who have not recently been ill. The current article describes a direct replication of this study using a sample of 402 individuals from the University of Michigan, the University of Glasgow, and Vrije Universiteit Amsterdam-more than 4 times the sample size of the original study. No effect of illness recency on attentional bias for disfigured faces emerged. Though it did not support the original finding, this replication provides suggestions for future research on the psychological underpinnings of pathogen avoidance.

Kin recognition and perceived facial similarity.

Facial similarity between individuals informs kinship judgments in third-party kin recognition. Indeed, one study found that similarity and kinship judgments encapsulate the same information (Maloney & Dal Martello, 2006). Yet, another study found that this is not the case when comparing adult face pairs of different sex (DeBruine et al., 2009). We replicated these studies to further clarify the role of facial similarity in kin recognition. We recruited 318 raters, who were shown 50 sibling pairs and 50 age- and sex-matched unrelated pairs ranging from 3 to 17 years old. Each rater was randomly assigned to make either kinship judgments ("related" or "unrelated") or similarity judgments (scale from 0 [not very similar] to 10 [very similar]). The threshold model found that performance in both tasks was equally accurate, with participants detecting child siblings in the kinship task above chance and giving significantly higher similarity ratings to siblings in the similarity task. In both tasks, opposite-sex siblings were perceived to be siblings less often than same-sex siblings, and judgments of unrelated face pairs were not affected by the sex of faces. Conversely, the effect of age difference within pairs of faces differed for the two tasks: a greater age difference decreased all kinship judgments, but only decreased similarity judgments of siblings, not unrelated pairs. In line with DeBruine et al. (2009), these findings suggest that similarity and kinship judgments are highly correlated but not strictly synonymous. The OSF Pre-registration Challenge for this project can be found at osf.io/ps9hy and the data at osf.io/sef9k.

Does the interaction between partnership status and average progesterone level predict women's preferences for facial masculinity?

Many studies have attempted to identify biological factors that reliably predict individual differences in women's preferences for masculine male faces. Marcinkowska et al. (2018, Hormones & Behavior) recently reported that women's (N = 102) preferences for facial masculinity were predicted by the interaction between their relationship status (partnered versus unpartnered) and average progesterone level. Because previous findings for between-women differences in masculinity preferences have often not replicated well, we attempted to replicate Marcinkowska et al.'s result in an open data set from another recent study that had not tested this hypothesis (Jones et al., 2018, Psychological Science). In this sample of 316 women, we found that facial masculinity preferences were predicted by the interaction between women's relationship status and average progesterone level, consistent with Marcinkowska et al.'s results (data and analysis code are available at https://osf.io/q9szc). Together, these findings suggest that the combined effects of relationship status and average progesterone level may predict facial masculinity preferences relatively reliably.

Facial masculinity is only weakly correlated with handgrip strength in young adult women.

OBJECTIVES: Ancestrally, strength is likely to have played a critical role in determining the ability to obtain and retain resources and the allocation of social status among humans. Responses to facial cues of strength are therefore thought to play an important role in human social interaction. Although many researchers have proposed that sexually dimorphic facial morphology is reliably correlated with physical strength, evidence for this hypothesis is somewhat mixed. Moreover, to date, only one study has investigated the putative relationship between facial masculinity and physical strength in women. Consequently, we tested for correlations between handgrip strength and objective measures of face-shape masculinity. METHODS: 531 women took part in the study. We measured each participant's handgrip strength (dominant hand). Sexual dimorphism of face shape was objectively measured from each face photograph using two methods: discriminant analysis and vector analysis. These methods use shape components derived from principal component analyses of facial landmarks to measure the probability of the face being classified as male (discriminant analysis method) or to locate the face on a female-male continuum (vector analysis method). RESULTS: Our analyses revealed that handgrip strength is, at best, only weakly correlated with facial masculinity in women. There was a weak significant association between handgrip strength and one measure of women's facial masculinity. The relationship between handgrip strength and our other measure of women's facial masculinity was not significant. DISCUSSION: Together, these results do not support the hypothesis that face-shape masculinity is an important cue of physical strength, at least in women.

A Data-Driven Test for Cross-Cultural Differences in Face Preferences.

Previous research has shown strong cross-cultural agreement in facial attractiveness judgments. However, these studies all used a theory-driven approach in which responses to specific facial characteristics are compared between cultures. This approach is constrained by the predictions that can be derived from existing theories and can therefore bias impressions of the extent of cross-cultural agreement in face preferences. We directly addressed this problem by using a data-driven, rather than theory-driven, approach to compare facial attractiveness judgments made by Chinese-born participants who were resident in China, Chinese-born participants currently resident in the UK, and UK-born and UK-resident White participants. Analyses of the principal components along which faces naturally varied suggested that Chinese and White UK participants used face information in different ways, at least when judging women's facial attractiveness. In other words, the data-driven approach used in this study revealed some cross-cultural differences in face preferences that were not apparent in studies using theory-driven approaches.

Contribution of shape and surface reflectance information to kinship detection in 3D face images.

Previous research has established that humans are able to detect kinship among strangers from facial images alone. The current study investigated what facial information is used for making those kinship judgments, specifically the contribution of face shape and surface reflectance information (e.g., skin texture, tone, eye and eyebrow color). Using 3D facial images, 195 participants were asked to judge the relatedness of 100 child pairs, half of which were related and half of which were unrelated. Participants were randomly assigned to judge one of three stimulus versions: face images with both surface reflectance and shape information present (reflectance and shape version), face images with shape information removed but surface reflectance present (reflectance version), or face images with surface reflectance information removed but shape present (shape version). Using binomial logistic mixed models, we found that participants were able to detect relatedness at levels above chance for all three stimulus versions. Overall, both individual shape and surface reflectance information contribute to kinship detection, and both cues are optimally combined when presented together. Preprint, preregistration, code, and data are available on the Open Science Framework (osf.io/7ftxd).

Individual-specific mortality is associated with how individuals evaluate future discounting decisions.

How organisms discount the value of future rewards is associated with many important outcomes, and may be a central component of theories of life-history. According to life-history theories, prioritizing immediacy is indicative of an accelerated strategy (i.e. reaching reproductive maturity quickly and producing many offspring at the cost of long-term investment). Previous work extrapolating life-history theories to facultative calibration of life-history traits within individuals has theorized that cues to mortality can trigger an accelerated strategy; however, compelling evidence for this hypothesis in modern humans is lacking. We assessed whether country-level life expectancy predicts individual future discounting behaviour across multiple intertemporal choice items in a sample of 13 429 participants from 54 countries. Individuals in countries with lower life expectancy were more likely to prefer an immediate reward to one that is delayed. Individuals from countries with greater life expectancy were especially more willing to wait for a future reward when the relative gain in choosing the future reward was large and/or the delay period was short. These results suggest that cues to mortality can influence the way individuals evaluate intertemporal decisions, which in turn can inform life-history trade-offs. We also found that older (but not very old) participants were more willing to wait for a future reward when there is a greater relative gain and/or shorter delay period, consistent with theoretical models that suggest individuals are more future-orientated at middle age.

No Compelling Evidence that Preferences for Facial Masculinity Track Changes in Women's Hormonal Status.

Although widely cited as strong evidence that sexual selection has shaped human facial-attractiveness judgments, findings suggesting that women's preferences for masculine characteristics in men's faces are related to women's hormonal status are equivocal and controversial. Consequently, we conducted the largest-ever longitudinal study of the hormonal correlates of women's preferences for facial masculinity ( N = 584). Analyses showed no compelling evidence that preferences for facial masculinity were related to changes in women's salivary steroid hormone levels. Furthermore, both within-subjects and between-subjects comparisons showed no evidence that oral contraceptive use decreased masculinity preferences. However, women generally preferred masculinized over feminized versions of men's faces, particularly when assessing men's attractiveness for short-term, rather than long-term, relationships. Our results do not support the hypothesized link between women's preferences for facial masculinity and their hormonal status.

No clear evidence for correlations between handgrip strength and sexually dimorphic acoustic properties of voices.

OBJECTIVES: Recent research on the signal value of masculine physical characteristics in men has focused on the possibility that such characteristics are valid cues of physical strength. However, evidence that sexually dimorphic vocal characteristics are correlated with physical strength is equivocal. Consequently, we undertook a further test for possible relationships between physical strength and masculine vocal characteristics. METHODS: We tested the putative relationships between White UK (N = 115) and Chinese (N = 106) participants' handgrip strength (a widely used proxy for general upper-body strength) and five sexually dimorphic acoustic properties of voices: fundamental frequency (F0), fundamental frequency's SD (F0-SD), formant dispersion (Df), formant position (Pf), and estimated vocal-tract length (VTL). RESULTS: Analyses revealed no clear evidence that stronger individuals had more masculine voices. CONCLUSIONS: Our results do not support the hypothesis that masculine vocal characteristics are a valid cue of physical strength.

Are physiological and behavioral immune responses negatively correlated? Evidence from hormone-linked differences in men's face preferences.

Behaviors that minimize exposure to sources of pathogens can carry opportunity costs. Consequently, how individuals resolve the tradeoff between the benefits and costs of behavioral immune responses should be sensitive to the extent to which they are vulnerable to infectious diseases. However, although it is a strong prediction of this functional flexibility principle, there is little compelling evidence that individuals with stronger physiological immune responses show weaker behavioral immune responses. Here we show that men with the combination of high testosterone and low cortisol levels, a hormonal profile recently found to be associated with particularly strong physiological immune responses, show weaker preferences for color cues associated with carotenoid pigmentation. Since carotenoid cues are thought to index vulnerability to infectious illnesses, our results are consistent with the functional flexibility principle's prediction that individuals with stronger physiological immune responses show weaker behavioral immune responses.

Sex-Specificity in the Reward Value of Facial Attractiveness.

Studies of the sex-specificity of sexual arousal in adults (i.e., the tendency to respond more strongly to preferred-sex individuals than non-preferred sex individuals) have suggested that heterosexual men, homosexual men, and homosexual women show stronger sex-specific responses than do heterosexual women. Evidence for a similar pattern of results in studies investigating the reward value of faces is equivocal. Consequently, we investigated the effects of (1) sexual orientation (homosexual vs. heterosexual), (2) sex (male vs. female), (3) image sex (preferred-sex vs. non-preferred-sex), and (4) the physical attractiveness of the individual shown in the image on the reward value of faces. Participants were 130 heterosexual men, 130 homosexual men, 130 heterosexual women, and 130 homosexual women. The reward value of faces was assessed using a standard key-press task. Multilevel modeling of responses indicated that images of preferred-sex individuals were more rewarding than images of non-preferred-sex individuals and that this preferred-sex bias was particularly pronounced when more physically attractive faces were presented. These effects were not qualified by interactions involving either the sexual orientation or the sex of our participants, however, suggesting that the preferred-sex bias in the reward value of faces is similar in heterosexual men, homosexual men, heterosexual women, and homosexual women.

Women's facial attractiveness is related to their body mass index but not their salivary cortisol.

OBJECTIVES: Although many theories of human facial attractiveness propose positive correlations between facial attractiveness and measures of actual health, evidence for such correlations is somewhat mixed. Here we sought to replicate a recent study reporting that women's facial attractiveness is independently related to both their adiposity and cortisol. METHODS: Ninety-six women provided saliva samples, which were analyzed for cortisol level, and their height and weight, which were used to calculate their body mass index (BMI). A digital face image of each woman was also taken under standardized photographic conditions and rated for attractiveness. RESULTS: There was a significant negative correlation between women's facial attractiveness and BMI. By contrast, salivary cortisol and facial attractiveness were not significantly correlated. CONCLUSIONS: Our results suggest that the types of health information reflected in women's faces include qualities that are indexed by BMI but do not necessarily include qualities that are indexed by cortisol. Am. J. Hum. Biol. 28:352-355, 2016. © 2015 Wiley Periodicals, Inc.

Women's Preference for Attractive Makeup Tracks Changes in Their Salivary Testosterone.

Previous research suggests that women's motivation to appear attractive is increased around the time of ovulation. However, the specific hormonal correlates of within-woman changes in motivation to appear attractive have not been investigated. To address this issue, we used a longitudinal design and a data-driven visual preference task. We found that women's preference for attractive makeup increases when their salivary testosterone levels are high. The relationship between testosterone level and preference for attractive makeup was independent of estradiol level, progesterone level, and estradiol-to-progesterone ratio. These results suggest that testosterone may contribute to changes in women's motivation to wear attractive makeup and, potentially, their motivation to appear attractive in general. Our results are also consistent with recent models of the role of testosterone in social behavior, according to which testosterone increases the probability of behaviors that could function to support the acquisition of mates and competition for resources.

The reward value of infant facial cuteness tracks within-subject changes in women's salivary testosterone.

"Baby schema" refers to infant characteristics, such as facial cues, that positively influence cuteness perceptions and trigger caregiving and protective behaviors in adults. Current models of hormonal regulation of parenting behaviors address how hormones may modulate protective behaviors and nurturance, but not how hormones may modulate responses to infant cuteness. To explore this issue, we investigated possible relationships between the reward value of infant facial cuteness and within-woman changes in testosterone, estradiol, and progesterone levels. Multilevel modeling of these data showed that infant cuteness was more rewarding when women's salivary testosterone levels were high. Moreover, this within-woman effect of testosterone was independent of the possible effects of estradiol and progesterone and was not simply a consequence of changes in women's cuteness perceptions. These results suggest that testosterone may modulate differential responses to infant facial cuteness, potentially revealing a new route through which testosterone shapes selective allocation of parental resources.

Reported maternal tendencies predict the reward value of infant facial cuteness, but not cuteness detection.

The factors that contribute to individual differences in the reward value of cute infant facial characteristics are poorly understood. Here we show that the effect of cuteness on a behavioural measure of the reward value of infant faces is greater among women reporting strong maternal tendencies. By contrast, maternal tendencies did not predict women's subjective ratings of the cuteness of these infant faces. These results show, for the first time, that the reward value of infant facial cuteness is greater among women who report being more interested in interacting with infants, implicating maternal tendencies in individual differences in the reward value of infant cuteness. Moreover, our results indicate that the relationship between maternal tendencies and the reward value of infant facial cuteness is not due to individual differences in women's ability to detect infant cuteness. This latter result suggests that individual differences in the reward value of infant cuteness are not simply a by-product of low-cost, functionless biases in the visual system.

Allocentric kin recognition is not affected by facial inversion.

Typical judgments involving faces are disrupted by inversion, with the Thatcher illusion serving as a compelling example. In two experiments, we examined how inversion affects allocentric kin recognition-the ability to judge the degree of genetic relatedness of others. In the first experiment, participants judged whether pairs of photographs of children portrayed siblings or unrelated children. Half of the pairs were siblings, half were unrelated. In three experimental conditions, photographs were viewed in upright orientation, flipped around a horizontal axis, or rotated 180°. Neither rotation nor flipping had any detectable effect on allocentric kin recognition. In the second experiment, participants judged pairs of photographs of adult women. Half of the pairs were sisters, half were unrelated. We again found no significant effect of facial inversion. Unlike almost all other face judgments, judgments of kinship from facial appearance do not rely on perceptual cues disrupted by inversion, suggesting that they rely more on spatially localized cues rather than "holistic" cues. We conclude that kin recognition is not simply a byproduct of other face perception abilities. We discuss the implications for cue combination models of other facial judgments that are affected by inversion.

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.

Sex ratio influences the motivational salience of facial attractiveness.

The sex ratio of the local population influences mating-related behaviours in many species. Recent experiments show that male-biased sex ratios increase the amount of financial resources men will invest in potential mates, suggesting that sex ratios influence allocation of mating effort in humans. To investigate this issue further, we tested for effects of cues to the sex ratio of the local population on the motivational salience of attractiveness in own-sex and opposite-sex faces. We did this using an effort-based key-press task, in which the motivational salience of facial attractiveness was assessed in samples of faces in which the ratio of male to female images was manipulated. The motivational salience of attractive opposite-sex, but not own-sex, faces was greater in the own-sex-biased (high competition for mates) than in the opposite-sex-biased (low competition for mates) condition. Moreover, this effect was not modulated by participant sex. These results present new evidence that sex ratio influences human mating-related behaviours. They also present the first evidence that the perceived sex ratio of the local population may modulate allocation of mating effort in women, as well as men.