Insect stridulations, amphibian choruses, bird songs, and mammalian vocalizations – among other acoustic signals and cues – play a major role in a broad range of animal taxa. In addition to communicating, e.g., the presence of a predator, or the position and distance to a food source, animal acoustic cues and signals broadcast a wealth of information about the caller, which allows the receiver to assess the potential mate value of an individual of the opposite sex or weigh the risk posed by a prospective rival (see Bradbury and Vehrencamp, 2011).

In primates, vocalizations are produced by the vibration of the vocal folds as air passes through and the resulting pulses are further modified by the structure of supralaryngeal elements (Taylor et al., 2016). In human adults, the larynx and supralaryngeal structures are sexually dimorphic (Lieberman, 1986; Taylor et al., 2016) and the resulting acoustic signals reflect such sex differences. Typically, adult male and female voices differ in mean fundamental frequency (e.g., Bachorowski and Owren, 1999; Feinberg et al., 2018; Aung and Puts, 2020) – the mean vibration frequency of the vocal folds (Ghazanfar and Rendall, 2008) – and formant frequencies (e.g., Fant, 1966; Puts et al., 2012; Cartei et al., 2014) – the resonances of the vibrating air in the vocal tract during speech production (Ghazanfar and Rendall, 2008). While the former is mainly determined by the length and mass of the vocal folds, the latter are determined by the length and cross-sectional area of the vocal tract (Lieberman, 1986; Ghazanfar and Rendall, 2008). Although male and female voices also differ in other acoustic attributes, studies addressing voice dimorphism have usually focused on F0 and related variables, and formant frequencies or derived indices, e.g., formant dispersion (Df) – the average distance between successive formants (Fitch, 1997) – and formant position (Pf) – the average standardized formant value for the first – usually four – formants (Puts et al., 2012).

Male voice pitch – the perceptual correlate of F0 (Ghazanfar and Rendall, 2008) – is affected by sex hormones throughout development. In this direction, for instance, male voice pitch was found to correlate with self- and third-party-rated masculinity (Pereira et al., 2019). During puberty, an increase in testosterone levels drives the thickening of the vocal cords, which in turn results in a significant drop in voice pitch (Evans et al., 2008); similar effects are also observed during testosterone therapy in female-to-male gender transitioning (Irwig et al., 2016). In addition to the effects on the vocal cords, testosterone has important anabolic and ergogenic properties (Handelsman et al., 2018); because of this, several studies have explored the association of dimorphic voice attributes with strength and/or physical dominance. Previous studies found a negative association of male F0 (Hodges-Simeon et al., 2014; Mailhos et al., 2022), Pf (Puts et al., 2012), and the standard deviation of the fundamental frequency (Puts et al., 2012) with physical strength. Other studies, however, failed to find a link between these variables (Sell et al., 2010; Atkinson et al., 2012; Han et al., 2018).

Although in modern societies interpersonal conflicts are rarely settled by fighting or physical strength, physical formidability has been linked to perceived dominance and authority. It has been proposed that physical formidability might have become associated with social status, leadership, and dominance over the course of human evolution (Murray, 2014; Lukaszewski et al., 2016). In this regard, Ko et al. (2015) observed that participants who were assigned to a more powerful role in a negotiation game showed a lower and more monotone pitch than participants assigned to a less powerful role. Similarly, in group settings, it has been observed that raising one’s pitch early during a negotiation predicted a low rank, while a decrease in voice pitch was associated with a high emerging rank (Cheng et al., 2016). In line with these results, Leongómez et al. (2017) observed that males and females who were low in self-perceived dominance increased their pitch more in the presence of a dominant listener than when interacting with a neutral one.

A growing body of evidence suggests that voice attributes are also related to perceived trustworthiness and fidelity. Low-pitched voices have been associated with perceived trustworthiness both in males and females (Tsantani et al., 2016; Schild et al., 2019). However, while Schild and colleagues also observed a significant negative association between mean fundamental frequency and reported infidelity, they did not find a link between voice attributes and trustworthy behavior in economic games. Furthermore, in a recent meta-analysis, these authors found that a lower mean F0 – i.e., voice pitch – might be indeed a valid cue for self-reported infidelity (Schild et al., 2021).

Other studies have explored the association between voice attributes and reproductive success, or some of its proxies, in humans. Apicella et al. (2007) observed a negative association between fundamental frequency and actual reproductive success, i.e., the number of children born to Hadza men – but not to women – even after controlling for age. Similarly, Puts et al. (2006) found a trend where male participants with lower F0 reported a higher number of sexual partners – this trend, however, was found not to be statistically significant. In mammals, including the human species, males can greatly increase their reproductive success by inseminating a large number of females (Buss, 1998), hence the current or desired number of sexual partners or sociosexuality orientation measurements have been used as proxies of reproductive success in males. In the same vein, Hughes et al. (2004) found that opposite-sex ratings of voice attractiveness were negatively correlated with the age of first sexual intercourse, and the reported number of sex partners and extra-pair copulations both in males and females. In turn, Hill et al. (2013) showed that vocal masculinity – a compound measure of voice pitch and formant dispersion – interacts with physical dominance to significantly predict mating success in males. Furthermore, a recent meta-analysis that explored the association of voice pitch and the mating domain – mating attitudes and behavior – in males showed a significant association of those variables (r = 0.132 [0.061,0.204], q = 0.0012; Lidborg et al., 2022). Notwithstanding the former results, other studies reported an association between voice attributes and the reproductive domain in females, but not in males. Atkinson et al. (2012), for instance, found that F0 was a predictor of different reproductive success indicators, including the number of children and grandchildren, in Himba females, but not males.

The groundbreaking work of Kinsey et al. (1948, 1953) allowed for the identification of individual differences in sociosexual behavior and attitudes, including frequency of actual and preferred sexual intercourse, number of actual and preferred sexual partners, and tendency to engage in uncommitted sexual relationships. Simpson and Gangestad (1991) developed the Sociosexual Orientation Inventory (SOI), one of the most widely used instruments to measure this internal dimension or tendency towards unrestricted sociosexual behavior. Sex differences in sociosexuality are generally large and have been observed cross-culturally, although such differences might be modulated environmentally (Schmitt, 2005). That is, sex differences seem to be larger in demanding reproductive environments, whereas sex differences in sociosexuality are more moderate in countries with more political and economic gender equality. Penke and Asendorpf (2008) proposed a revised version of the original one-dimensional SOI– the Revised Sociosexual Orientation Inventory (SOI-R) – and showed that sociosexuality consists of three facets: sociosexual behavior, attitude, and desire, rather than a single dimension. Interestingly, Valentova et al. (2019) observed that male speech F0 was negatively associated with sociosexuality in males but not in females; the relationship between male singing F0 and sociosexuality was, however, inverted.

This study was aimed, thus, at furthering our understanding of the role of human voice cues in mating behavior. To achieve this, we explored the association of several dimorphic attributes of the human voice – i.e., mean fundamental frequency, formant position, and formant dispersion – with the different facets of sociosexual orientation, i.e., sociosexual behavior, attitude, and desire, as measured by SOI-R (Penke and Asendorpf, 2008).

Descriptive statistics of the speakers’ sociosexual and acoustic variables used in this study are shown in Table 1. A Mann–Whitney test showed significant differences in mean fundamental frequency, formant position, and formant dispersion between male and female voices. Similarly, males and females differed in all three dimensions of sociosexuality (SOIR1: sociosexual behavior; SOIR2: sociosexual attitude; and SOIR3: sociosexual desire).

Because acoustic and sociosexual variables were not normally distributed, in order to analyze the relationship between these variables, Spearman rank correlation coefficients were calculated. Tables 2, 3 show the correlations between sociosexual and acoustic variables for males and females, respectively.

Mean fundamental frequency (F0) showed a significant negative correlation with sociosexual behavior (SOIR1) in males but not in females, and formant position exhibited a significant negative correlation with sociosexual desire (SOIR3).

The confidence intervals of all correlations were calculated by means of bootstrapping with 10,000 iterations. All significant correlations were supported by this analysis (see Supplementary Tables S1, S2). In addition, the correlation between male Pf and sociosexual behavior (SOIR1) that approached significance by Spearman rank correlation analysis (r₁₀₀ = −0.22, p = 0.076), reached statistical significance by estimation of the confidence intervals for this correlation (95% CI [−0.406, −0.025]).

Because age showed significant correlations with both Df and sociosexual behavior in females, partial Spearman rank correlations were calculated. After controlling for age, only the correlation between F0 and sociosexual behavior in males, and the correlation between Pf and sociosexual desire in males remain significant (see Table 4).

Voice pitch, the perceptual correlate of mean F0, is one of the most salient features of the human voice and it is also one of the attributes that show the highest degree of sexual dimorphism. Prior studies point to a role of voice pitch in both intrasexual competition and intersexual selection processes. Our results show a negative correlation between mean fundamental frequency and sociosexual behavior – as measured by the behavior facet of the Revised Sociosexual Orientation Inventory (Penke and Asendorpf, 2008) – in males (r₁₀₀ = −0.27, p = 0.023; 95%CI = [−0.45, −0.07]) but not in females (r₁₄₇ = −0.17_, p = 0.103, 95%CI = [−0.32, −0.00]); in other words, our findings show a trend where men with lower-pitched voices exhibit a more unrestricted sexual behavior. This association is in line with previous studies which have shown that male-speech lower F0 is related to higher scores on the SOI-R scale (Valentova et al., 2019; Stern et al., 2021) and that males with lower-pitched voices have higher reproductive success and more children born to them (Apicella et al., 2007). While Stern et al. (2021) did find an association between voice pitch and sociosexuality in women, neither the studies by Apicella et al. (2007) and Valentova et al. (2019) nor the present study found an association between female F0 and sociosexuality.

As mentioned before, F0 and other male voice attributes have been found to provide relevant cues to several biologically relevant attributes of the speaker (e.g., height, physical strength, dominance, trustworthiness, but also self-reported infidelity). Given that male and female reproductive strategies differ – while male reproductive strategies seem to be quantity-oriented, female strategies appear to be quality-oriented – male cues play an important role in reproductive behavior informing receptive females about the mate value of their potential mates.

Sociosexual behavior has been proposed to reflect an individual’s overall allocation of effort (e.g., time, energy, or money) to short-term versus long-term mating strategies (Penke and Asendorpf, 2008). Thus, the correlation between F0 and sociosexual behavior might reflect this internal disposition of the male speakers. Alternatively, because sociosexual behavior (facet 1 of SOI-R) is a composite score that takes into account the number of sexual partners in the last 12 months, lifetime number of single-occasion sexual partners, and number of sexual encounters without an interest in a long-term committed relationship (Penke and Asendorpf, 2008), this variable may as well be affected by the potential partners’ disposition to have sex with the respondent. In this scenario, the correlation between F0 and sociosexual behavior might be in line with previous studies which have shown a consistent female preference for lower-pitched male voices (for a review, see: Pisanski and Feinberg, 2018). Such a preference might be the result of the negative association of voice pitch with body size and physical formidability (Pisanski et al., 2014; Aung and Puts, 2020) which are generally thought to be honest indicators of a male’s ability to pass genes that will increase the survival or reproductive success of her offspring.

The Spearman rank correlation analysis between Pf and sociosexual behavior (SOIR1) and correlation confidence intervals study for this correlation produced mixed results. That is, while the first failed to reach significance, the confidence intervals analysis seems to support a significant correlation between the variables. Further studies will be needed to confirm or reject the true association of the variables. Once again, since Pf has been associated with desirable male attributes, this feature of the male voice may contribute to broadcasting the genetic quality or physiological state of the male to potential mates; or this might simply result from the joint action of male sexual hormones on the brain – thus promoting more typical male behaviors – and peripheric structures.

This study also shows that Pf is associated with sociosexual desire – a motivational state characterized by sexual interest often linked to subjective sexual arousal and sexual fantasies (Penke and Asendorpf, 2008). While the association between voice pitch and sociosexual behavior in males may reflect an adaptive role of F0 in signaling fighting ability or biological quality to potential rivals or mates – that is, males with lower F0 may have a higher number of sexual partners by deterring romantic rivals or by attracting romantic partners – it is more difficult to think of an adaptive function of broadcasting sexual desire. We think the latter correlation probably relies on the simple fact that vocal cords and the neural structures involved in sexual motivation in males are under the effect of the same androgenizing hormones.

Some shortcomings of the present study should be mentioned. The current study analyzes only some of the most widely used acoustic variables. We cannot rule out the possibility that other variables, on their own, or via complex interaction patterns may reflect more accurately an individual’s sociosexuality. In addition, the sample used in this study consisted exclusively of university students; in the future, a more representative sample should be included. Also, while it poses some methodological problems, we believe the use of free speech in a dating or seduction context would much better reflect a person’s sociosexual behavior.

Finally, future research may focus on testing these results in different language groups, and exploring whether the reported association of sociosexual behavior and desire with acoustic features of the male voice are perceptually relevant.

To conclude, in this study, we identified a significant association between F0 and sociosexual behavior, and between Pf and sociosexual desire in males but not in females. While we cannot rule out the possibility that these associations reflect the joint effects of male sex hormones on both the brain and peripheral anatomic structures, our findings are consistent with a role of male voice attributes in advertising desirable genetic and/or physiological attributes for potential mates. By analyzing the relationship between acoustic features of the human voice and sociosexual behavior in a sample of native Spanish-speaking men and women, this study contributes to furthering our understanding of the role of the human voice in the reproductive domain.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

The studies involving human participants were reviewed and approved by Comité de Ética de Investigación, Facultad de Psicología, Universidad de Murcia. The patients/participants provided their written informed consent to participate in this study.

AM and FM-S proposed and designed the study. AM, FM-S, and D-AE-C collected the data. AM and ÁC conducted the data analysis. AM, FM-S, and ÁC wrote the manuscript. All authors contributed to the article and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.