Androstadienone, a Chemosignal Found in Human Sweat, Increases Individualistic Behavior and Decreases Cooperative Responses in Men

The Roles of Androgens in Humans: Biology, Metabolic Regulation and Health

Androgens are an important and diverse group of steroid hormone molecular species. They play varied functional roles, such as the control of metabolic energy fate and partition, the maintenance of skeletal and body protein and integrity and the development of brain capabilities and behavioral setup (including those factors defining maleness). In addition, androgens are the precursors of estrogens, with which they share an extensive control of the reproductive mechanisms (in both sexes). In this review, the types of androgens, their functions and signaling are tabulated and described, including some less-known functions. The close interrelationship between corticosteroids and androgens is also analyzed, centered in the adrenal cortex, together with the main feedback control systems of the hypothalamic-hypophysis-gonads axis, and its modulation by the metabolic environment, sex, age and health. Testosterone (T) is singled out because of its high synthesis rate and turnover, but also because age-related hypogonadism is a key signal for the biologically planned early obsolescence of men, and the delayed onset of a faster rate of functional losses in women after menopause. The close collaboration of T with estradiol (E2) active in the maintenance of body metabolic systems is also presented Their parallel insufficiency has been directly related to the ravages of senescence and the metabolic syndrome constellation of disorders. The clinical use of T to correct hypoandrogenism helps maintain the functionality of core metabolism, limiting excess fat deposition, sarcopenia and cognoscitive frailty (part of these effects are due to the E2 generated from T). The effectiveness of using lipophilic T esters for T replacement treatments is analyzed in depth, and the main problems derived from their application are discussed.

Humans and the Olfactory Environment: A Case of Gene-Culture Coevolution?

As hunter-gatherers, humans used their sense of smell to identify plants and animals, to find their way within a foraging area, or to distinguish each other by gender, age, kinship, or social dominance. Because women gathered while men hunted, the sexes evolved different sensitivities to plant and animal odors. They also ended up emitting different odors. Male odors served to intimidate rival males or assert dominance. With the rise of farming and sedentism, humans no longer needed their sense of smell to find elusive food sources or to orient themselves within a large area. Odors now came from a narrower range of plants and animals. Meanwhile, body odor was removed through bathing to facilitate interactions in enclosed spaces. This new phenotype became the template for the evolution of a new genotype: less sensitivity to odors of wild plants and animals, lower emissions of male odors, and a more negative response to them. Further change came with the development of fragrances to reodorize the body and the home. This new olfactory environment coevolved with the ability to represent odors in the mind, notably for storage in memory, for vicarious re-experiencing, or for sharing with other people through speech and writing.

The scent of emotions: A systematic review of human intra- and interspecific chemical communication of emotions

OBJECTIVE

The sense of olfaction has been considered of minor importance in human communication. In recent years, evidence has emerged that humans might be influenced by unconscious messages sent through chemosignals in body odors. Data concerning the ability of humans to recognize fear, maybe related to the evolutionary role of these emotions in the fight-or-flight reactions, are well known.

METHODS

To further understand the role of emotional chemosignals in mediating communication in humans and its influence on animal behaviors, we conducted a systematic literature review.

RESULTS

Chemosignals derived from axillary odors collected under a variety of emotional stimuli and sad tears in humans affect receivers' social interactions, danger detection and risk-taking behavior, social aspects of eating, and performance under stressing conditions. In addition, beyond the fight-or-flight response, even the body odors of happiness can be perceived by others. Furthermore, human chemosignals can influence behaviors and stressful responses in animals, particularly dogs and horses, which may partially explain their special relationship with humans.

CONCLUSION

Our review highlights the importance of chemosignaling in human intra- and interspecific interactions and suggests the need for further investigations, both in physiological conditions and in patients with psychiatric or neurodegenerative disorders.

Androstadienone resulted in a rightward shift of women's preference for sexually dimorphic male faces across the continuum of femininity-masculinity

As a derivative of testosterone, androstadienone (AND) can influence human psychological and physiological states. To explore the influence of AND on women's preferences for male sexual dimorphic faces in a mate-choice context, we asked 52 females in the luteal phase to choose one from four sexual dimorphic male faces in a long-term and short-term context while inhaling 250 μm of AND or a placebo odor on two consecutive days. Results revealed that participants had a greater and lesser preference for the +30% masculinized and 60% feminized faces, respectively, while inhaling AND, as compared to when inhaling the placebo. The AND intervention resulted in a rightward shift of the women's preference for male sexual dimorphic faces across the continuum of femininity-masculinity. The current findings highlight that AND may influence women's preference for male sexually dimorphic faces in a mate-choice context.

Androstadienone, a putative chemosignal of dominance, increases gaze avoidance among men with high social anxiety

Socially anxious individuals show increased sensitivity toward social threat signals, including cues of dominance. This sensitivity may account for the hypervigilance and gaze avoidance commonly reported in individuals with social anxiety. This study examines visual scanning behavior in response to androstadienone (androsta-4,16,-dien-3-one), a putative chemosignal of dominance. We tested whether exposure to androstadienone would increase hypervigilance and gaze avoidance among individuals with high social anxiety. In a double-blind, placebo-controlled, within-subject design, 26 participants with high social anxiety and 26 with low social anxiety were exposed to androstadienone and a control solution on two separate days. On each day, an eye-tracker recorded their spontaneous scanning behavior while they viewed facial images of men depicting dominant and neutral poses. The results indicate that among participants with high social anxiety, androstadienone increased gaze avoidance by reducing the percentage of fixations made to the eye-region and the total amount of time spent gazing at the eye-region of the faces. Participants with low social anxiety did not show this effect. These findings indicate that androstadienone serves as a threatening chemosignal of dominance, further supporting the link between hypersensitivity toward social threat cues and the perpetuation of social anxiety.

Women's fertility cues affect cooperative behavior: Evidence for the role of the human putative chemosignal estratetraenol

Previous studies demonstrating that women's body odor during ovulation is perceived as more attractive suggest that exposure to women's chemosignals of high fertility increases mating motivation. Building on previous evidence showing that cooperative behaviors are perceived as attractive, in the current study we investigated whether chemosignals of women's fertility affect men's tendency to behave cooperatively. In the first experiment we found that in the presence of women's body odor during ovulation, men increase their tendency to apply a cooperative strategy, while their tendency to apply an individualistic strategy decreases. To examine the mechanism underlying this effect, we tested a different sample of men exposed to the putative human pheromone estratetraenol (estra-1,3,5(10),16-tetraen-3-ol) or to a control solution. Exposure toestratetraenol compared with control yielded strikingly similar effects of increased cooperation. The results indicate that women's chemosignals of high fertility increase mating motivation among man, encouraging them to act in a cooperative manner toward others, a response that may highlight their attractive qualities and thus attract mates. We further conclude that estratetraenol may serve as one of the biological agents that mediate the behavioral effects of women's chemosignals of fertility on social behavior.

Effects of androstadienone on dominance perception in males with low and high social anxiety

Increasing evidence suggests that humans can communicate both trait-dominance and state-dominance via body odor. Androstadienone (androsta-4,16,-dien-3-one), a chemosignal found in human sweat, seems to be a likely candidate for signaling dominance in humans. The aim of the current study was to investigate the effects of androstadienone on the perception of social dominance. Moreover, we examined whether high levels of social anxiety, a psychopathology involving concerns that specifically pertain to social dominance, are associated with increased sensitivity to androstadienone as a chemical cue of dominance. In a double-blind, placebo-controlled, within-subject design, 64 heterosexual male participants (32 with high social anxiety and 32 with low social anxiety) viewed facial images of males depicting dominant, neutral and submissive postures, and were asked to recognize and rate the dominance expressed in those images. Participants completed the task twice, once under exposure to androstadienone and once under exposure to a control solution. The results indicate that androstadienone increased the perceived dominance of men's faces, specifically among participants with high social anxiety. These findings suggest a direct influence of androstadienone on dominance perception and further highlight the preferential processing of dominance and social threat signals evident in social anxiety.