Abstract: Chemical communication plays an important role in the social interactions and mating behavior of diverse animal taxa; yet its role in humans remains equivocal. Using a randomized, placebo-controlled experiment involving 243 male participants, we test whether exposure to synthetic copulin – a mixture of volatile fatty acids secreted vaginally in primates, increases 1) men’s sexual motivation using an incentivized behavioral task, 2) self-reported willingness to take sexual risks, 3) preference for short-term mating, 4) perceptions of female attractiveness and 5) self-reported mate value. Because chemical receptors are found throughout the body and human chemosensory pathways have yet to be definitively identified, we also manipulate the location of copulin exposure (i.e. olfactory epithelium versus epidermal keratinocytes in the genital region). Finally, we examine whether prior sexual experience mediate any behavioral effects. Unlike previous reports, we fail to find any effects of copulin exposure on measures of men’s sexual behavior.
Abstract: Olfaction and chemical signaling play an important role in the mating behaviors of many taxa, yet there is minimal empirical research on human putative pheromones. A mixture of five volatile fatty acids secreted vaginally, identified and named ‘‘copulins,’’ significantly increase in concentration during the follicular phase and decrease in concentration during the luteal phase in nonpill using women. Men exposed to copulins exhibit an increase in testosterone, are inhibited in discriminating the attractiveness of women’s faces, and behave less cooperatively. According to Anisogamy, Sexual Selection and Parental Investment Theory, mammalian males, having low cost and high benefit from any copulatory interaction, may adaptively utilize any useful cues to identifying ovulating females and adjust their behavior accordingly in order to maximize their potential reproductive success. In the current study, we attempted a replication of Ju ̈tte and Grammer’s finding indicating copulins inhibit the ability of men to discriminate attractiveness of women’s faces, and we examined the role of copulins in self-reported mate-guarding behaviors and self-perceived sexual desirability. We utilized a randomized placebo-controlled design and as predicted, results indicated men exposed to copulins were more likely to rate themselves as sexually desirable to women and, on average, the copulin group rated women’s faces as more attractive than controls. There were no significant findings with mate guarding.
“Body odor affects mate quality estimations and motivational systems alter approach-avoidance behavior based on these estimations”
Abstract: Chemical communication is sensationalized in the media and promoted in the form of pheromones heavily marketed as aphrodisiacs. Yet, chemical communication is a highly contentious area of research in human biology and psychology stemming from the lack of theoretical frameworks on which to build and test hypotheses relating to the chemosensory communicative effects on social behavior (e.g., mating, kin-detection, alliance formation). The definition of chemical signal is rife too with controversy and while chemical communication is the most ubiquitous mode of communication on the planet, disbelief in human usage of chemical molecules for communication prevails. Here, I answer two questions: (1) Do volatile chemical molecules released at the body surface affect estimates of mate quality and, (2) if so, by what mechanism? I posit an information processing system that integrates functionally relevant chemical inputs into an estimation of an individual’s mate quality and, based on that estimation, the interacting motivational systems sexual disgust and sexual arousal cause predictable behavioral outputs in others. In this model, specific chemical molecule(s) are not proposed as potential pheromones. Instead, the model focuses solely on what information is represented in human body odor (e.g. stable and dynamic characteristics like sex and pathogen load, respectively), how this information is integrated into an assessment of mate quality, and what motivational systems and subsequently behavioral sequences are activated based on the mate quality estimation.
“Hunter-gatherers reveal the role of experience and familiarity on preferences for averageness in faces” (with Anthony Little and Coren Apicella)
Abstract: One of the strongest and most robust findings in psychological research on attractiveness is the preference for average faces — faces with proportions close to the mean of a population. A second and related phenomenon is the preference for familiar items (e.g. the mere-exposure effect), which may contribute to the appeal of averageness. Here we examine the role of experience and familiarity on preferences for averageness in a relatively isolated hunter-gatherer population: the Hadza. Previous work has found that while Hadza prefer more averaged Hadza faces they do not show a preference for more average Caucasian faces, probably since they have little experience with these faces. In study 1, we similarly find that the Hadza also show no preference for mixed-race faces (Caucasian and Hadza blends). In study 2 however, we demonstrate that experience with individual faces produces a preference for composites made up of those faces. In study 3, we expose participants to Caucasian faces exhibiting a discontinuous bi-modal distribution on a given trait where one mode for the trait was more frequent but less extreme than the second mode. We used two traits eye-spacing and skin color. We find that participants preferred the average of the traits to which they were exposed rather than the more frequent or novel versions. Across conditions however, there was a familiarity effect where participants were more likely to choose the frequently occurring trait. Together these studies suggest that the preference for averageness is universal, experience-dependent and distinct from the preference for familiarity. While humans may show an aversion to novel and extreme traits in others, preferences for the traits themselves are relatively flexible and shaped by experience.