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.     

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.     

Children aged 7–9 prefer cuteness in baby faces,and femininity in women's faces

Infant facial features are typically perceived as “cute,” provoking caretaking behaviours. Previous research has focused on adults' perceptions of baby cuteness, and examined how these perceptions are influenced by events of the adult reproductive lifespan, such as ovulation and menopause. However, globally, individuals of all ages, including pre-pubertal children, provide notable proportions of infant care. In this study, we recruited participants in and around northern England, and tested 330 adults and 65 children aged 7–9 using a forced-choice paradigm to assess preferences for infant facial cuteness in two stimulus sets and (as a control task) preferences for femininity in women's faces. We analysed the data with Hierarchical Bayesian Regression Models. The adults and children successfully identified infants who had been manipulated to appear cuter, although children's performance was poorer than adults' performance, and children reliably identified infant cuteness in only one of the two infant stimuli sets. Children chose the feminised over masculinised women's faces as more attractive, although again their performance was poorer than adults' performance. There was evidence for a female advantage in the tasks: girls performed better than boys when assessing the woman stimuli and one of the infant stimulus sets, and women performed better than men when assessing one of the infant stimulus sets. There was no evidence that cuteness judgements differed depending upon exposure to infants (children with siblings aged 0–2; adults with a baby caregiving role), or depending upon being just younger or older than the average age of menopause. Children and grandparents provide notable portions of infant caretaking globally, and cuteness perceptions could direct appropriate caregiving behaviour in these age groups, as well as in adults of reproductive age.     

Adults' responses to infants varying in perceived cuteness

The effects of perceived cuteness of infant photographs on the behaviour of young adults was investigated. Looking, facial muscle activity, and skin conductance were measured during individual presentations of the photographs, whereas only looking was measured during paired presentations. Both measures of looking time were significantly affected by the perceived cuteness of infant photographs, with infants ranked as most cute looked at longest and those ranked least cute looked at for the shortest length of time. Increased facial muscle activity previously associated with pleasant or happy facial expressions was associated with presentations of infant photographs but was not related to perceived cuteness. A second experiment indicated that increased facial muscle activity was specific to infant photographs. Adult responses to infant physical appearance appear to be regulated by two mechanisms: an initial positive response to “babyishness”, reflected by increased facial zygomaticus muscle activity, and an individual cognitive preference response to “cuteness”, reflected by differential looking times.     

Female and male responses to cuteness,age and emotion in infant faces

Neonatal features in the newborn are thought to trigger parental care, the most fundamental prosocial behaviour. The underlying mechanisms that release parental care have not yet been resolved. Here we report sex differences in the ability to discriminate cues to cuteness despite equivalence in the capability to discriminate age and facial expression. These differences become apparent in a task where adults were asked to choose the cuter of two babies. While women could reliably choose the cuter infant, men had more difficulty in doing so. When showing the exact same face pairs but asking to choose the younger or the happier baby, there was no sex difference. These results suggest that the sex difference in the ability to discriminate cues to cuteness in infants underlies female-specific emotive responses. We argue that this reactivity expressed by women evolved to ensure that a female allocates her caretaking resources to her youngest offspring while it needs mothering care.     

Men's Preferences for Women's Femininity in Dynamic Cross-Modal Stimuli

Men generally prefer feminine women''s faces and voices over masculine women''s faces and voices, and these cross-modal preferences are positively correlated. Men''s preferences for female facial and vocal femininity have typically been investigated independently by presenting soundless still images separately from audio-only vocal recordings. For the first time ever, we presented men with short video clips in which dynamic faces and voices were simultaneously manipulated in femininity/masculinity. Men preferred feminine men''s faces over masculine men''s faces, and preferred masculine men''s voices over feminine men''s voices. We found that men preferred feminine women''s faces and voices over masculine women''s faces and voices. Men''s attractiveness ratings of both feminine and masculine faces were increased by the addition of vocal femininity. Also, men''s attractiveness ratings of feminine and masculine voices were increased by the addition of facial femininity present in the video. Men''s preferences for vocal and facial femininity were significantly and positively correlated when stimuli were female, but not when they were male. Our findings complement other evidence for cross-modal femininity preferences among male raters, and show that preferences observed in studies using still images and/or independently presented vocal stimuli are also observed when dynamic faces and voices are displayed simultaneously in video format.     

The motivational salience of infant faces is similar for men and women

Infant facial features are thought to be powerful elicitors of caregiving behaviour. It has been widely assumed that men and women respond in different ways to those features, such as a large forehead and eyes and round protruding cheeks, colloquially described as 'cute'. We investigated experimentally potential differences using measures of both conscious appraisal ('liking') and behavioural responsivity ('wanting') to real world infant and adult faces in 71 non-parents. Overall, women gave significantly higher 'liking' ratings for infant faces (but not adult faces) compared to men. However, this difference was not seen in the 'wanting' task, where we measured the willingness of men and women to key-press to increase or decrease viewing duration of an infant face. Further analysis of sensitivity to cuteness, categorising infants by degree of infantile features, revealed that both men and women showed a graded significant increase in both positive attractiveness ratings and viewing times to the 'cutest' infants. We suggest that infant faces may have similar motivational salience to men and women, despite gender idiosyncrasies in their conscious appraisal.     

Evidence of adaptation for mate choice within women's memory

Sexually dimorphic characteristics in men may act as cues, advertising long-term health, dominance, and reproductive potential to prospective mates. Evolution has accordingly adapted human cognition so that women perceive sexually dimorphic facial features as important when judging the attractiveness and suitability of potential mates. Here we provide evidence showing, for the first time, that women's memory for details encountered in recently experienced episodes is also systematically biased by the presence of men's facial cues signaling enhanced or reduced sexual dimorphism. Importantly, the direction and strength of this bias are predicted by individual differences in women's preferences for masculine versus feminine facial features in men and are triggered specifically while viewing images of male but not female faces. No analogous effects were observed in male participants viewing images of feminized and masculinized women's faces despite the fact that male participants showed strong preferences for feminized facial features. These findings reveal a preference-dependent memory enhancement in women that would promote retention of information from encounters with preferred potential mates. We propose that women's memory for recently experienced episodes may therefore be functionally specialized for mate choice and in particular for the comparative evaluation of alternative potential mates. This also raises the possibility that similar specialization may be present in other species where it has been established that precursor, ‘episodic-like’ forms of memory exist.     

Facial shape provides a valid cue to sociosexuality in men but not women

Existing work suggests that observers' perceptions of sociosexuality from strangers' faces are positively associated with individuals' self-reported sociosexuality. However it is not clear what cues observers use to form these judgements. Over two studies we examined whether sociosexuality is reflected in faces, which cues contain information about sociosexuality, and whether observers' perceptions of sociosexuality from faces are positively associated with individuals' self-reported sociosexuality. In Study One, Geometric Morphometric Modelling (GMM) analysis of 103 Caucasian participants revealed that self-reported sociosexuality was predicted by facial morphology in male but not female faces. In Study Two, 65 Caucasian participants judged the sociosexuality of opposite sex faces (faces from Study One) at zero acquaintance. Perceived sociosexuality predicted self-reported sociosexuality for men, but not women. Participants were also presented with composites of faces of individuals with more unrestricted sociosexuality paired with composites of faces of individuals with more restricted sociosexuality and asked to indicate which was more unrestricted. Participants selected the more unrestricted sociosexuality male, but not female, facial composites at rates significantly above chance. GMM analyses also found that facial morphology statistically significantly predicted perceived sociosexuality in women's and, to a greater extent, in men's faces. Finally, facial shape mediated the relationship between perceived sociosexuality and self-reported sociosexuality in men's but not women's faces. Our results suggest that facial shape acts as a valid cue to sociosexuality in men's but not women's faces.     

The influence of infant facial cues on adoption preferences

Trivers’s theory of parental investment suggests that adults should decide whether or not to invest in a given infant using a cost-benefit analysis. To make the best investment decision, adults should seek as much relevant information as possible. Infant facial cues may serve to provide information and evoke feelings of parental care in adults. Four specific infant facial cues were investigated: resemblance (as a proxy for kinship), health, happiness, and cuteness. It was predicted that these cues would influence feelings of parental care for both sexes, but that resemblance would be more important for men than women because of the importance of paternity uncertainty in the ancestral environment. Seventy-six men and 76 women participated in a hypothetical adoption task in which they made judgments of infant faces. Average zero-order, partial, and component score correlations all revealed that men placed primary emphasis on cues of resemblance, while women placed primary emphasis on cues of health and cuteness (cues of infant quality). The correlations also showed that men placed a significantly greater emphasis on cues of resemblance than did women. This research was supported by a Queen’s University Graduate Award (first author) and a Senior Research Fellowship from the Ontario Mental Health Foundation (second author). Anthony Volk is a Ph.D. candidate at Queen’s University, studying parental investment. Vernon L. Quinsey is a professor of psychology and psychiatry at Queen’s University. His research focuses on forensic and evolutionary psychology. An erratum to this article is available at .     

Manipulation of Infant‐Like Traits Affects Perceived Cuteness of Infant,Adult and Cat Faces

Physical traits that are characteristic of human infants are referred to as baby‐schema, and the notion that these affect perception of cuteness and elicit care giving from adults has a long history. In this study, infant‐similarity was experimentally manipulated using the difference between adult and infant faces. Human infant, human adult and cat faces were manipulated to look more (human) infant‐like or adult‐like. The results from the current study demonstrate the impact of infant‐similarity on human adults' perception of cuteness across the three different types of face. The type of face had a large impact on perceived cuteness in line with the expected infant‐similarity of the images. Infants and cats were cutest while adults were less cute. The manipulations of infant‐similarity, however, had similar effects on the perception of cuteness across all three types of face. Faces manipulated to have infant‐like traits were rated as cuter than their equivalents manipulated to have adult‐like traits. These data demonstrate that baby‐like traits have a powerful hold over human perceptions and that these effects are not simply limited to infant faces.     

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 men''s preference for femininity in women''s 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 men''s preferences. Using an average femininity preference for each country, we found men''s 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.     

Environment contingent preferences: Exposure to visual cues of direct male–male competition and wealth increase women's preferences for masculinity in male faces

Previous studies show that parasite prevalence and mortality/health are related to cultural variation in women's preferences for attractive and masculine traits in men. Other studies have suggested that both male–male competition and wealth may also be important correlates of cross-cultural variation in women's masculinity preferences. Here we examined whether exposure to cues of direct male–male competition, violence, or wealth influenced women's face preferences. We showed women slideshows of images with cues of low and high direct male–male competition/violence or wealth and measured their visual preferences for masculine face traits. Recent visual experience changed women's preferences for facial masculinity, with women preferring more masculine male faces after exposure to images of men engaged in direct physical competition, images of weapons, or images depicting items of high monetary value. Recent visual experience had no significant effects on preferences for masculinity in same-sex faces. Given that high levels of direct physical competition and violence among males may increase the importance of direct intra-sexual competition, it may be adaptive for women to shift visual preferences in favor of males with face cues indicating physical strength and dominance over investment in such environments. Similarly, in wealthy environments investment may be less important than other aspects of quality and so it may be adaptive for women to shift visual preferences in favor of males with face cues indicating other aspects of quality over investment. Overall, our data demonstrate that preferences can be strategically flexible according to recent visual experience and support the notion of environment contingent preferences.     

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.     

Differential Reward Learning for Self and Others Predicts Self-Reported Altruism

In social environments, decisions not only determine rewards for oneself but also for others. However, individual differences in pro-social behaviors have been typically studied through self-report. We developed a decision-making paradigm in which participants chose from card decks with differing rewards for themselves and charity; some decks gave similar rewards to both, while others gave higher rewards for one or the other. We used a reinforcement-learning model that estimated each participant''s relative weighting of self versus charity reward. As shown both in choices and model parameters, individuals who showed relatively better learning of rewards for charity – compared to themselves – were more likely to engage in pro-social behavior outside of a laboratory setting indicated by self-report. Overall rates of reward learning, however, did not predict individual differences in pro-social tendencies. These results support the idea that biases toward learning about social rewards are associated with one''s altruistic tendencies.     

Regional brain responses in nulliparous women to emotional infant stimuli

Infant cries and facial expressions influence social interactions and elicit caretaking behaviors from adults. Recent neuroimaging studies suggest that neural responses to infant stimuli involve brain regions that process rewards. However, these studies have yet to investigate individual differences in tendencies to engage or withdraw from motivationally relevant stimuli. To investigate this, we used event-related fMRI to scan 17 nulliparous women. Participants were presented with novel infant cries of two distress levels (low and high) and unknown infant faces of varying affect (happy, sad, and neutral) in a randomized, counter-balanced order. Brain activation was subsequently correlated with scores on the Behavioral Inhibition System/Behavioral Activation System scale. Infant cries activated bilateral superior and middle temporal gyri (STG and MTG) and precentral and postcentral gyri. Activation was greater in bilateral temporal cortices for low- relative to high-distress cries. Happy relative to neutral faces activated the ventral striatum, caudate, ventromedial prefrontal, and orbitofrontal cortices. Sad versus neutral faces activated the precuneus, cuneus, and posterior cingulate cortex, and behavioral activation drive correlated with occipital cortical activations in this contrast. Behavioral inhibition correlated with activation in the right STG for high- and low-distress cries relative to pink noise. Behavioral drive correlated inversely with putamen, caudate, and thalamic activations for the comparison of high-distress cries to pink noise. Reward-responsiveness correlated with activation in the left precentral gyrus during the perception of low-distress cries relative to pink noise. Our findings indicate that infant cry stimuli elicit activations in areas implicated in auditory processing and social cognition. Happy infant faces may be encoded as rewarding, whereas sad faces activate regions associated with empathic processing. Differences in motivational tendencies may modulate neural responses to infant cues.     

Facial attractiveness is related to women's cortisol and body fat,but not with immune responsiveness

Recent studies suggest that facial attractiveness indicates immune responsiveness in men and that this relationship is moderated by stress hormones which interact with testosterone levels. However, studies testing whether facial attractiveness in women signals their immune responsiveness are lacking. Here, we photographed young Latvian women, vaccinated them against hepatitis B and measured the amount of specific antibodies produced, cortisol levels and percentage body fat. Latvian men rated the attractiveness of the women''s faces. Interestingly, in women, immune responsiveness (amount of antibodies produced) did not predict facial attractiveness. Instead, plasma cortisol level was negatively associated with attractiveness, indicating that stressed women look less attractive. Fat percentage was curvilinearly associated with facial attractiveness, indicating that being too thin or too fat reduces attractiveness. Our study suggests that in contrast to men, facial attractiveness in women does not indicate immune responsiveness against hepatitis B, but is associated with two other aspects of long-term health and fertility: circulating levels of the stress hormone cortisol and percentage body fat.     

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

It has been proposed that women's 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 women's 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 − 17 days 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 women's preferences for a potential sexual partner's facial masculinity fluctuate throughout the cycle.     

Men's facial masculinity predicts changes in their female partners' sexual interests across the ovulatory cycle,whereas men's intelligence does not

A substantial body of work demonstrates that women's mate preferences change across the ovulatory cycle. When fertile in their cycles, women are especially attracted to masculine features (e.g., faces, voices, bodies), socially dominant behavior, and male scents associated with body symmetry and social dominance. Women may also find intelligent men particularly attractive when fertile, though findings are mixed. Related research shows that, on average, romantically-involved women report stronger sexual attraction to men other than their pair-bond partners, but not partners, when fertile, and especially when their partners lack features fertile women prefer (e.g., symmetry). In the current study, we examined whether women's patterns of sexual interests across the cycle are similarly moderated by partners' facial masculinity, facial attractiveness, and intelligence. Results revealed predicted effects of male partners’ facial masculinity but none for partners’ intelligence. Facial attractiveness may have effects, but we find no evidence that it does so independently of facial masculinity.     

Re-evaluating the relationship between pathogen avoidance and preferences for facial symmetry and sexual dimorphism: A registered report

Over the past decade, a small literature has tested how trait-level pathogen-avoidance motives (e.g., disgust sensitivity) and exposure to pathogen cues relate to preferences for facial symmetry and sexual dimorphism. Results have largely been interpreted as suggesting that the behavioral immune system influences preferences for these features in potential mates. However, findings are limited by small sample sizes among studies reporting supportive evidence, the use of small stimulus sets to assess preferences for symmetry and dimorphism, and design features that render implications for theory ambiguous (namely, largely only investigating women's preferences for male faces). Using a sample of 954 White young adult UK participants and a pool of 100 White young adult stimuli, the current registered report applied a standard two-alternative forced-choice approach to evaluate both men's and women's preferences for both facial symmetry and dimorphism in both same- and opposite-sex targets. Participants were randomly assigned to either a pathogen prime or a control prime, and they completed instruments assessing individual differences in pathogen avoidance (disgust sensitivity and contamination sensitivity). Results revealed overall preferences for both facial symmetry and dimorphism. However, they did not reveal a relation between these preferences and disgust sensitivity or contamination sensitivity, nor did they reveal differences in these preferences across control and pathogen prime conditions. Null results of pathogen-avoidance variables were consistent across participant sex, target sex, and interactions between participant sex and target sex. Overall, findings cast doubt on the hypothesis that pathogen-avoidance motives influence preferences for facial symmetry or dimorphism.