Effects of testosterone on speech production and perception: Linking hormone levels in males to vocal cues and female voice attractiveness ratings.

This study sets out to investigate the potential effect of males' testosterone level on speech production and speech perception. Regarding speech production, we investigate intra- and inter-individual variation in mean fundamental frequency (fo) and formant frequencies and highlight the potential interacting effect of another hormone, i.e. cortisol. In addition, we investigate the influence of different speech materials on the relationship between testosterone and speech production. Regarding speech perception, we investigate the potential effect of individual differences in males' testosterone level on ratings of attractiveness of female voices. In the production study, data is gathered from 30 healthy adult males ranging from 19 to 27 years (mean age: 22.4, SD: 2.2) who recorded their voices and provided saliva samples at 9 am, 12 noon and 3 pm on a single day. Speech material consists of sustained vowels, counting, read speech and a free description of pictures. Biological measures comprise speakers' height, grip strength, and hormone levels (testosterone and cortisol). In the perception study, participants were asked to rate the attractiveness of female voice stimuli (sentence stimulus, same-speaker pairs) that were manipulated in three steps regarding mean fo and formant frequencies. Regarding speech production, our results show that testosterone affected mean fo (but not formants) both within and between speakers. This relationship was weakened in speakers with high cortisol levels and depended on the speech material. Regarding speech perception, we found female stimuli with higher mean fo and formants to be rated as sounding more attractive than stimuli with lower mean fo and formants. Moreover, listeners with low testosterone showed an increased sensitivity to vocal cues of female attractiveness. While our results of the production study support earlier findings of a relationship between testosterone and mean fo in males (which is mediated by cortisol), they also highlight the relevance of the speech material: The effect of testosterone was strongest in sustained vowels, potentially due to a strengthened effect of hormones on physiologically strongly influenced tasks such as sustained vowels in contrast to more free speech tasks such as a picture description. The perception study is the first to show an effect of males' testosterone level on female attractiveness ratings using voice stimuli.

A premium for positive social interest and attractive voices in the acceptability of unfair offers? An ERP study.

Although the attractiveness of voices plays an important role in social interactions, it is unclear how voice attractiveness and social interest influence social decision-making. Here, we combined the ultimatum game with recording event-related brain potentials (ERPs) and examined the effect of attractive versus unattractive voices of the proposers, expressing positive versus negative social interest ("I like you" vs. "I don't like you"), on the acceptance of the proposal. Overall, fair offers were accepted at significantly higher rates than unfair offers, and high voice attractiveness increased acceptance rates for all proposals. In ERPs in response to the voices, their attractiveness and expressed social interests yielded early additive effects in the N1 component, followed by interactions in the subsequent P2, P3 and N400 components. More importantly, unfair offers elicited a larger Medial Frontal Negativity (MFN) than fair offers but only when the proposer's voice was unattractive or when the voice carried positive social interest. These results suggest that both voice attractiveness and social interest moderate social decision-making and there is a similar "beauty premium" for voices as for faces.

Voice attractiveness and decision making in third-party punishment.

This study examined the impact of an attractive voice compared to an unattractive voice in an economic game. Results showed that proposers with an attractive voice were perceived as more reasonable in their monetary allocations and were less likely to receive punishment for unfair allocation.

Dominance of face over voice in human attractiveness judgments: ERP evidence.

The attractiveness of a person, a complex, and socially relevant type of information, is transmitted in many ways, not least through face and voice. However, it is unclear how the stimulus domains carrying attractiveness information interact. The present study explored the audiovisual perception of attractiveness in a Stroop-like paradigm using event-related potentials (ERPs). Participants were presented with face-voice pairs carrying congruent or incongruent attractiveness information and, in turn, judged the attractiveness level of each domain while ignoring the other. Voice attractiveness judgments were influenced by unattended face attractiveness, in terms of both, early perceptual encoding (N170, P200) as well as later evaluative stages (N400, LPC). In contrast, effects of unattended voice attractiveness on face attractiveness judgments were confined to early perceptual encoding (N170). These results demonstrate not only the interaction of multiple domains in human attractiveness perception at different processing stages but also a relative dominance of face over voice attractiveness.

The "beauty premium" effect of voice attractiveness of long speech sounds in outcome-evaluation event-related potentials in a trust game.

Previous research suggested that people with attractive voices had an advantage in economic games, even if the voices were only presented for 400 ms. The present study investigated the influence of voice attractiveness on the cooperative trust behavior with longer exposure times to the voices. Event-related potentials (ERPs) were recorded during the feedback outcome evaluation. Participants heard a voice of the partner for 2,040 ms and decided whether to invest to the partner for a possibility to gain more money. The results showed that participants made more invest choices to the attractive partners, replicating the "beauty premium" effect of the attractive voices. Moreover, participants were more likely to invest to male partners. The ERP analysis for the outcome showed that the difference waves of feedback-related negativity (FRN) amplitude were smaller in the attractive voice condition than in the unattractive voice condition, suggesting that the rewarding effect of attractive voices weakened the frustrating feelings of the loss. In sum, the present study confirms that attractive voices with longer presentation durations facilitate cooperative behavior and modulate the processing of feedback evaluations.

Content matters: Cyclic effects on women's voices depend on social context.

Women's voices reportedly sound more attractive during the fertile days compared to the non-fertile days of their menstrual cycle. Here we investigated whether the speech content modulates the cyclic changes in women's voices. We asked 72 men and women to rate how interested they were in getting to know the speaker based on her voice. Forty-two naturally cycling women were recorded once during the late follicular phase (high fertility) and once during the luteal phase (low fertility) while speaking sentences of neutral and social content. Listeners were more interested in getting to know the speakers when hearing sentences with social content. Furthermore, raters were more interested in getting to know the speakers when these were recorded in the late follicular than in the luteal phase, but only in sentences with social content. Notably, levels of reproductive hormones (EP ratio) across the cycle phases did not significantly predict the preference for late follicular voices, but echoing the perceptual ratings, there was a significant EP ratio x speech content interaction. Phonetic analyses of mean fundamental frequency (F0) revealed a main effect of menstrual cycle phase and speech content but no interaction. Employing an action-oriented task, the present study extends findings of cycle-dependent voice changes by emphasising that speech content critically modulates fertility effects.

Human voice attractiveness processing: Electrophysiological evidence.

Voice attractiveness plays a significant role in social interaction and mate choice. However, how listeners perceive attractive voices and whether this process is mandatory, is poorly understood. The current study explores this question using event-related brain potentials. Participants listened to syllables spoken by male and female voices with high or low attractiveness while completing an implicit (voice un-related) tone detection task or explicitly judging voice attractiveness. In both tasks, attractive male voices elicited a larger N1 than unattractive voices. However, an effect of voice attractiveness on the late positive complex (LPC) was only seen in the explicit task but it was present to both same- and opposite-sex voices. Taken together, voice attractiveness processing during early stages appears to be rapid and mandatory and related to mate selection, whereas during later elaborated processing, voice attractiveness is strategic and aesthetics-based, requiring attentional resources.

Fertility-Dependent Acoustic Variation in Women's Voices Previously Shown to Affect Listener Physiology and Perception.

Previous research demonstrates that listeners perceive women's voices as more attractive when recorded at high compared to low fertility phases of the menstrual cycle. This effect has been repeated with multiple voice recording samples, but one stimuli set has shown particularly robust replications. First collected by Pipitone and Gallup (2008), women were recorded counting from 1-10 on approximately the same day and time once a week for 4 weeks. Repeatedly, studies using these recordings have shown that naturally cycling women recorded at high fertility are rated as more attractive compared to voices of the same women at low fertility. Additionally, these stimuli have been shown to elicit autonomic nervous system arousal and precipitate a rise in testosterone levels among listeners. Although previous studies have examined the acoustic properties of voices across the menstrual cycle, they reach little consensus. The current study evaluates Pipitone and Gallup's voice stimuli from an acoustic perspective, analyzing specific vocal characteristics of both naturally cycling women and women taking hormonal contraceptives. Results show that among naturally cycling women, variation in vocal amplitude (shimmer) was significantly lower in high fertility recordings compared to the women's voices at low fertility. Harmonics-to-noise ratio and variation in voice pitch (jitter) also fluctuated systematically across voices sampled at different times during the menstrual cycle, though these effects were not statistically significant. It is possible that these acoustic changes could account for some of the replicated perceptual, hormonal, and physiological changes documented in prior literature using these voice stimuli.

Interactions between observer and stimuli fertility status: Endocrine and perceptual responses to intrasexual vocal fertility cues.

Both men and women find female voices more attractive at higher fertility times in the menstrual cycle, suggesting the voice is a cue to fertility and/or hormonal status. Preference for fertile females' voices provides males with an obvious reproduction advantage, however the advantage for female listeners is less clear. One possibility is that attention to the fertility status of potential rivals may enable women to enhance their own reproductive strategies through intrasexual competition. If so, the response to having high fertility voices should include hormonal changes that promote competitive behavior. Furthermore, attention and response to such cues should vary as a function of the observer's own fertility, which influences her ability to compete for mates. The current study monitored variation in cortisol and testosterone levels in response to evaluating the attractiveness of voices of other women. All 33 participants completed this task once during ovulation then again during the luteal phase. The voice stimuli were recorded from naturally cycling women at both high and low fertility, and from women using hormonal birth control. We found that listeners rated high fertility voices as more attractive compared to low fertility, with the effect being stronger when listeners were ovulating. Testosterone was elevated following voice ratings suggesting threat detection or the anticipation of competition, but no stress response was found.

Your Cheatin' Voice Will Tell on You: Detection of Past Infidelity from Voice.

Evidence suggests that many physical, behavioral, and trait qualities can be detected solely from the sound of a person's voice, irrespective of the semantic information conveyed through speech. This study examined whether raters could accurately assess the likelihood that a person has cheated on committed, romantic partners simply by hearing the speaker's voice. Independent raters heard voice samples of individuals who self-reported that they either cheated or had never cheated on their romantic partners. To control for aspects that may clue a listener to the speaker's mate value, we used voice samples that did not differ between these groups for voice attractiveness, age, voice pitch, and other acoustic measures. We found that participants indeed rated the voices of those who had a history of cheating as more likely to cheat. Male speakers were given higher ratings for cheating, while female raters were more likely to ascribe the likelihood to cheat to speakers. Additionally, we manipulated the pitch of the voice samples, and for both sexes, the lower pitched versions were consistently rated to be from those who were more likely to have cheated. Regardless of the pitch manipulation, speakers were able to assess actual history of infidelity; the one exception was that men's accuracy decreased when judging women whose voices were lowered. These findings expand upon the idea that the human voice may be of value as a cheater detection tool and very thin slices of vocal information are all that is needed to make certain assessments about others.

Physiological changes in response to hearing female voices recorded at high fertility.

The human voice transmits pertinent information regarding health status and age, with recent evidence suggesting that it plays an important role in mate selection. However, the mechanism that drives preferences for voices of fertile females has yet to be elucidated. The current study examined the physiological changes that occur when listening to voices recorded from naturally cycling females at high and low fertility phases of the menstrual cycle, as well as from females using hormonal contraception. We found the voices of naturally cycling females recorded during a high fertility phase were rated as more attractive and produced the greatest increase in galvanic skin response (GSR). Heart rate (HR) also showed a trend towards the highest increase when listening to naturally cycling, high fertility female voices. There were no differences in ratings of voice attractiveness, GSR, or HR between the voices recorded from females using hormonal contraception. Analyzed separately, male and female listeners both showed a preference for naturally cycling, high fertility voices. Female listeners additionally showed increased GSR and HR responses to naturally cycling, high fertility voices. We discuss the adaptive benefits of detecting vocal changes for male as well as female listeners, and also discuss the role that the nervous system plays during human mate assessments.