Abstract: Research suggests that humans can communicate emotional states (e.g., fear, sadness) via chemosignals. However, thus far little is known about whether sexual arousal can also be conveyed through chemosignals and how these signals might influence the receiver. In three experiments, and a subsequent mini meta-analysis, support was found for the hypothesis that men can process the scent of sexually aroused women and that exposure to these sexual chemosignals affect the subsequent perceptions and sexual motivation of men. Specifically, Experiment 1 revealed that men evaluate the axillary sweat of sexually aroused women as more attractive, compared to the scent of the same women when not sexually aroused. In addition, Experiment 2 showed that exposure to sexual chemosignals increased the men’s sexual arousal. Experiment 3 found support for the thesis that exposure to sexual chemosignals would increase sexual motivation. As predicted, men devoted greater attention to and showed greater interest in mating with women who displayed sexual cues (e.g., scantily dressed, in seductive poses). By contrast, exposure to the sexual chemosignals did not alter males’ attention and mating interest toward women who displayed no sexual cues. It is discussed how sexual chemosignals may function as an additional channel in the communication of sexual interest and how contextual factors can influence the dynamics of human sexual communication.
General Discussion
The
present studies provide support for the hypothesis that men are
sensitive to olfactory signals of sexual arousal released by women.
Overall, Experiments 1–3 and a subsequent mini meta-analysis found that
men evaluated the scent of sexually aroused women as relatively more
attractive. Experiment 2 showed that these sexual chemosignals increased
men’s self-reported sexual arousal. Finally, Experiment 3 found support
for the hypothesis that the sexual chemosignals increased men’s
attention to and interest in women who displayed sexual cues.
Specifically, men spent relatively more time looking at women who
displayed sexual cues, and were more motivated to mate with them. Taken
together, the current findings are among the first to show that that
women’s sexual arousal led to the release of a distinctive scent that
increases men’s sexual motivation.
These findings are consistent with numerous studies, showing that emotional states (e.g., fear, disgust, sadness) produce olfactory signals that orient nearby recipients to the immediate environment and sensitize them to emotionally consistent cues (de Groot et al., 2012; Gelstein et al., 2011; Pause, 2012; Zhou & Chen, 2008). Sexual arousal in particular is both socially and fitness-relevant states, and there are clear interpersonal benefits to its communication for both the sender and the recipient, such as the signaling and detection of mating opportunities, as well as synchronizing mating behavior between partners (Schaller, Park, & Kenrick, 2007). The current research expands on the existing literature by showing that olfactory messages may serve as an additional channel of communication between humans, and in relevant mating contexts, sexual chemosignals may be released along with corresponding visual and auditory expressions of sexual interest to produce a stronger overall signal.
Interestingly, recent research by Hoffmann (2019) also found support for the thesis that men can process the scent of sexually aroused women. Specifically, men were exposed to axillary sweat (collected from women who were sexually aroused vs. not aroused) while the men listened to erotic stories, and the findings showed that the sexual scents elicited greater genital arousal in the men. However, this effect was only detected in response to female scents collected during the luteal phase of their cycle, but not their follicular phase. In contrast to the current studies, Hoffmann (2019) did not find an effect of female scent on men’s self-reported sexual arousal and sexual interest. Those results may have diverged from the findings reported here because of several procedural differences between the two research paradigms. Notably, in our experiments, the scent samples were collected and presented to recipients under different conditions. For instance, the female scent donors in our studies briefly exercised at the start of the experiment to create a similar base rate of physiological arousal in both conditions, in order to control for physiological arousal that is also elevated during sexual arousal. Additionally, in Experiments 2 and 3, men’s sexual arousal was assessed after exposing them to a block of multiple scent samples from either scent condition, rather than each time after exposure to one scent sample. Finally, the current experiments did not present male recipients with any additional sexual stimuli (i.e., an erotic story) in conjunction with the chemosensory primes (Hoffmann, 2019). Whether or not any of these factors contributed to the different findings is an important empirical question that deserves future investigation.
Most studies have examined emotional chemosignals secreted by the axillary regions because they are dense with apocrine glands that produce sweat in response to activation of the sympathetic nervous system (de Groot, Semin, & Smeets, 2014). However, apart from perspiration, there are other volatile body fluids (e.g., urine, sperm, lacrimal fluid) that likely play roles in olfactory signaling (Pause, 2012). For instance, research has shown that exposure to scents from the vulvar area (collected during the periovulatory phase) can increase testosterone secretion and sexual interest in men (Cerda-Molina et al., 2013). In light of the current findings, it would therefore be worth testing whether women’s sexual arousal level moderates men’s responses to scents from the vulvar area.
Additionally, it would be interesting to examine the influence of the context in which men are exposed to female scents. For example, as mentioned earlier, some research paradigms have primed a sexual context when exposing recipients to the scent stimuli (Alves-Oliveira et al., 2018; Hoffmann, 2019). That is, male scent recipients listened to an erotic story or watched audiovisual stimuli (Alves-Oliveira et al., 2018) during exposure to the scents, before measuring the men’s sexual arousal. Thus, men’s reactions to the sexual scents in these studies were always a product of both the olfactory and audiovisual stimuli. In contrast, our experiments showed that the olfactory stimuli alone can elicit a sexual response in recipients, in the absence of a conceptually similar prime in a different sensory modality. Although our findings highlight that sexual chemosignals alone can prime male sexual motivation, it is unclear whether additional sexual priming via different sensory modalities can elicit stronger sexual responses in men. Thus, future research may wish to further investigate the role of priming multiple sensory modalities on how recipients are influenced by sexual chemosignals.
The current research is not without limitations. Although the indices of sexual arousal and sexual motivation used in Experiments 2 and 3 established that men respond to female chemosignals, future work would do well to examine a wider range of measurements of subjective and physiological sexual arousal (e.g., Ciardha, Attard-Johnson, & Bindemann, 2018; Janssen, Prause, & Geer, 2007; Kukkonen, Binik, Amsel, & Carrier, 2007; Laws, 2009; McPhail et al., 2019). In addition, while our studies did not take the donors’ menstrual cycle into account, the recent findings of Hoffmann (2019) highlight that there is scope to further investigate the interaction between menstrual cycle phase and women’s axillary chemosignals, and the influence of these signals on male sexual arousal (see Hoffmann, 2019, for a full discussion of the results). Additionally, future research in chemosignal research would benefit from considering procedural differences in order to understand which factors tend to enhance and mitigate the effects of sexual chemosignals on recipients (Pause, 2012). Moreover, it is perhaps worth considering how sexual arousal chemosignals interact with individual factors we did not specifically examine, such as testosterone levels (Gangestad, Thornhill, & Garver-Apgar, 2010; Thornhill & Gangestad, 1999), or individual differences in disgust sensitivity (Haidt, McCauley, & Rozin, 1994; Stevenson, Case, & Oaten, 2011). Finally, future work could include a wider range of measures to monitor the emotions of the scent donors and the scent recipients during the experiment (de Groot et al., 2015b; Mitchell, DiBartolo, Brown, & Barlow, 1998).
Consistent with the growing evidence that emotional states can be communicated through scent, our findings provide evidence that humans can signal and process olfactory signals of sexual arousal. Importantly, the results showed that perceiving these sexual chemosignals alters the scent receiver’s sexual arousal and their interest and preference for potential mates. Informed by the present findings, we can envision a dynamic exchange of olfactory signals that, combined with corresponding visual and auditory expressions, are communicated between men and women during mating encounters. These encounters may thus entail more than meets the eye and we hope that the current findings encourage further research to examine the role of sexual olfactory signals in human communication.
These findings are consistent with numerous studies, showing that emotional states (e.g., fear, disgust, sadness) produce olfactory signals that orient nearby recipients to the immediate environment and sensitize them to emotionally consistent cues (de Groot et al., 2012; Gelstein et al., 2011; Pause, 2012; Zhou & Chen, 2008). Sexual arousal in particular is both socially and fitness-relevant states, and there are clear interpersonal benefits to its communication for both the sender and the recipient, such as the signaling and detection of mating opportunities, as well as synchronizing mating behavior between partners (Schaller, Park, & Kenrick, 2007). The current research expands on the existing literature by showing that olfactory messages may serve as an additional channel of communication between humans, and in relevant mating contexts, sexual chemosignals may be released along with corresponding visual and auditory expressions of sexual interest to produce a stronger overall signal.
Interestingly, recent research by Hoffmann (2019) also found support for the thesis that men can process the scent of sexually aroused women. Specifically, men were exposed to axillary sweat (collected from women who were sexually aroused vs. not aroused) while the men listened to erotic stories, and the findings showed that the sexual scents elicited greater genital arousal in the men. However, this effect was only detected in response to female scents collected during the luteal phase of their cycle, but not their follicular phase. In contrast to the current studies, Hoffmann (2019) did not find an effect of female scent on men’s self-reported sexual arousal and sexual interest. Those results may have diverged from the findings reported here because of several procedural differences between the two research paradigms. Notably, in our experiments, the scent samples were collected and presented to recipients under different conditions. For instance, the female scent donors in our studies briefly exercised at the start of the experiment to create a similar base rate of physiological arousal in both conditions, in order to control for physiological arousal that is also elevated during sexual arousal. Additionally, in Experiments 2 and 3, men’s sexual arousal was assessed after exposing them to a block of multiple scent samples from either scent condition, rather than each time after exposure to one scent sample. Finally, the current experiments did not present male recipients with any additional sexual stimuli (i.e., an erotic story) in conjunction with the chemosensory primes (Hoffmann, 2019). Whether or not any of these factors contributed to the different findings is an important empirical question that deserves future investigation.
Most studies have examined emotional chemosignals secreted by the axillary regions because they are dense with apocrine glands that produce sweat in response to activation of the sympathetic nervous system (de Groot, Semin, & Smeets, 2014). However, apart from perspiration, there are other volatile body fluids (e.g., urine, sperm, lacrimal fluid) that likely play roles in olfactory signaling (Pause, 2012). For instance, research has shown that exposure to scents from the vulvar area (collected during the periovulatory phase) can increase testosterone secretion and sexual interest in men (Cerda-Molina et al., 2013). In light of the current findings, it would therefore be worth testing whether women’s sexual arousal level moderates men’s responses to scents from the vulvar area.
Additionally, it would be interesting to examine the influence of the context in which men are exposed to female scents. For example, as mentioned earlier, some research paradigms have primed a sexual context when exposing recipients to the scent stimuli (Alves-Oliveira et al., 2018; Hoffmann, 2019). That is, male scent recipients listened to an erotic story or watched audiovisual stimuli (Alves-Oliveira et al., 2018) during exposure to the scents, before measuring the men’s sexual arousal. Thus, men’s reactions to the sexual scents in these studies were always a product of both the olfactory and audiovisual stimuli. In contrast, our experiments showed that the olfactory stimuli alone can elicit a sexual response in recipients, in the absence of a conceptually similar prime in a different sensory modality. Although our findings highlight that sexual chemosignals alone can prime male sexual motivation, it is unclear whether additional sexual priming via different sensory modalities can elicit stronger sexual responses in men. Thus, future research may wish to further investigate the role of priming multiple sensory modalities on how recipients are influenced by sexual chemosignals.
The current research is not without limitations. Although the indices of sexual arousal and sexual motivation used in Experiments 2 and 3 established that men respond to female chemosignals, future work would do well to examine a wider range of measurements of subjective and physiological sexual arousal (e.g., Ciardha, Attard-Johnson, & Bindemann, 2018; Janssen, Prause, & Geer, 2007; Kukkonen, Binik, Amsel, & Carrier, 2007; Laws, 2009; McPhail et al., 2019). In addition, while our studies did not take the donors’ menstrual cycle into account, the recent findings of Hoffmann (2019) highlight that there is scope to further investigate the interaction between menstrual cycle phase and women’s axillary chemosignals, and the influence of these signals on male sexual arousal (see Hoffmann, 2019, for a full discussion of the results). Additionally, future research in chemosignal research would benefit from considering procedural differences in order to understand which factors tend to enhance and mitigate the effects of sexual chemosignals on recipients (Pause, 2012). Moreover, it is perhaps worth considering how sexual arousal chemosignals interact with individual factors we did not specifically examine, such as testosterone levels (Gangestad, Thornhill, & Garver-Apgar, 2010; Thornhill & Gangestad, 1999), or individual differences in disgust sensitivity (Haidt, McCauley, & Rozin, 1994; Stevenson, Case, & Oaten, 2011). Finally, future work could include a wider range of measures to monitor the emotions of the scent donors and the scent recipients during the experiment (de Groot et al., 2015b; Mitchell, DiBartolo, Brown, & Barlow, 1998).
Consistent with the growing evidence that emotional states can be communicated through scent, our findings provide evidence that humans can signal and process olfactory signals of sexual arousal. Importantly, the results showed that perceiving these sexual chemosignals alters the scent receiver’s sexual arousal and their interest and preference for potential mates. Informed by the present findings, we can envision a dynamic exchange of olfactory signals that, combined with corresponding visual and auditory expressions, are communicated between men and women during mating encounters. These encounters may thus entail more than meets the eye and we hope that the current findings encourage further research to examine the role of sexual olfactory signals in human communication.
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