Nonhuman animals have long been known to communicate dominance and aggression through their vocalizations (Morton 1977). Lower frequency vocalizations are typically produced by relatively larger, more dominant individuals and are used by many animals to signal threat (Taylor and Reby 2010). Humans are no exception. Men’s fundamental frequency (F 0 , perceived as voice pitch) and vocal tract resonances or formant frequencies are significantly lower than women’s due mostly to sexual dimorphism in human vocal anatomy (Titze 1989). However, even at the within-sex level, larger or more dominant men and women typically produce lower fundamental and formant frequencies (i.e., lower pitched and more resonant speech) relative to their smaller, subordinate counterparts (Puts et al. 2012a). Listeners are in turn highly sensitive to these correspondences. In fact, in addition to associating low-frequency voices with greater physical size, strength, masculinity, and dominance (reviewed in Pisanski and Bryant 2019), listeners often associate low voice pitch with positive psychological traits such as competence and intelligence (Kreiman and Sidtis 2011 for review; cf. Hughes et al. 2014). These vocal stereotypes can have real-life implications affecting, for instance, who people prefer to vote for in a political election (Gregory Jr. and Gallagher 2002; Klofstad et al. 2015; Tigue et al. 2012) or to hire following a job interview (Schroeder and Epley 2015).

Men with relatively lower voice pitch and perhaps lower formants are often also judged as more attractive compared to men with relatively higher voice frequencies (Pisanski and Feinberg 2019 for review; Puts et al. 2016). In a professional context, both men and women with relatively low voice frequencies are typically judged as more dominant and competent (see e.g., Klofstad et al. 2012). Thus, a low-frequency voice may benefit men in a broad range of social contexts ranging from sexual to political and economic. This is not always the case among women, for whom, like men, low voice frequencies are perceived as masculine (Pisanski and Feinberg 2019), but can be considered unattractive (Feinberg 2008; Puts 2016). Indeed, most studies that have either experimentally manipulated voice frequencies or examined natural variation in nonverbal vocal parameters found that deeper voices are perceived as less attractive in women (Pisanski and Feinberg 2019; Puts et al. 2016). Nevertheless, several studies have found the opposite (Babel et al. 2014; Hughes et al. 2014; Pisanski et al. 2018; Tuomi and Fisher 1979), perhaps because deeper voices may signal sexual interest, maturity, confidence, and/or competence.

Humans can readily and volitionally modulate various nonverbal vocal parameters including their fundamental and formant frequencies (Pisanski et al. 2016a). Yet, despite a growing number of studies highlighting the social relevance of between-individual differences in voice production, few studies have examined vocal variation within individuals. The capacity for voice modulation in humans, in conjunction with evidence for strong vocal stereotypes that can have real life implications, poses the question of whether men and women modulate the frequency components of their voices in specific social contexts to elicit a desired social appraisal or outcome. Indeed, the rare capacity for humans (compared to other animals) to modulate the nonverbal parameters of the voice may have been selected for, and may confer various evolutionary and social advantages (Pisanski et al. 2016a).

A small number of lab-based studies examining voice modulation in socially relevant contexts, most within in a mating context, provide preliminary support for this hypothesis. For example, Puts et al. (2006) demonstrated voice pitch modulation among men taking part in a laboratory-based mock dating game. Men who rated a male competitor as more dominant relative to themselves raised their voice pitch compared to a control condition, whereas men who rated the competitor as less dominant lowered their voice pitch (± 2 Hz on average). Using the same dataset, Hodges-Simeon et al. (2010) found that the standard deviation of men’s fundamental frequency changed from baseline when speaking to a potential date as a function of the man’s self-rated relative dominance. Subsequent research has revealed that both sexes generally modulate their voice pitch when speaking to attractive members of the opposite sex (Fraccaro et al. 2011; Hughes et al. 2010, 2014; Leongómez et al. 2014). Pisanski et al. (2018) recently showed that men and women change their voice pitch during real life speed dating, depending both on whether they show a personal preference for their date, and on his or her overall desirability. Finally, Leongómez et al. (2017) demonstrated that interviewees modulated the pitch of their voices during mock interviews, raising their voice pitch in response to employers they perceived as dominant and prestigious. Several laboratory studies have also demonstrated that men and women can volitionally modulate their voices “on demand”, for example, when instructed to sound ‘confident, intelligent or dominant’ (Hughes et al. 2014), ‘masculine or feminine’ (Cartei et al. 2012), or ‘physically large or small’ (Pisanski et al. 2016c).

Yet, there remains limited evidence for context-dependent voice modulation in real-life social contexts, outside of the laboratory, where the mechanisms and outcomes may differ compared to voice modulation observed in more controlled settings. Much research has related voice modulation to the emotional content of speech (Scherer 2019 for recent review). Other research has sought to identify the patterns and natural sequences of voice modulations occurring when people interact. For instance, nonverbal vocal parameters can change within the same individual across the span of a single conversation or interview (Gregory et al. 1993), during oral examinations (Pisanski et al. 2016d), when lying (Ekman et al. 1976), or depending on the conversational partner (e.g., infant-directed speech: Wang et al. 2019). It is not entirely clear how much of these vocal changes are a consequence of emotional arousal, or a result of conscious voice modulation.

Anecdotal evidence also suggests that people manipulate their voices when taking a position of authority. For example, former British Prime Minister Margaret Thatcher reportedly lowered her voice pitch when delivering political speeches (Karpf 2006). However, very few studies have directly tested this hypothesis. Hunter and Titze (2010) examined teachers’ vocal intensity (voicing percentage per hour, loudness − dB SPL and fundamental frequency) during and after work hours. Occupational voicing percentage per hour was more than twice that of non-occupational, and occupational voices were higher in pitch. However, several elements of the study design (e.g., no experimental conditions, lack of control group, increased noise in a classroom as compared to home environment) limit firm conclusions regarding voice modulation when speaking authoritatively.

The present study was therefore designed to test (a) whether professional men and women alter their voice frequencies when speaking authoritatively about a topic on which they have specific expertise compared to when informally answering a common-knowledge question; (b) whether listeners judge the voices of these men and women as more competent and authoritative when giving expert advice than in the control condition; and (c) whether the production or perception of voice modulation differs for male versus female speakers.