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Faking It: The production, perception, and function of social voice modulation

Periodic Reporting for period 1 - Voice Modulation (Faking It: The production, perception, and function of social voice modulation)

Reporting period: 2016-02-01 to 2018-01-31

The project’s goal is to advance our understanding of the nature, functions, and social implications of voice modulation. The capacity to modulate nonverbal dimensions of the voice, including pitch and vocal tract resonances (see Figure I), requires complex neural control of the vocal anatomy. While rare in the animal kingdom, such vocal control is an essential prerequisite for articulated speech in humans. Yet, the extent to which humans modulate the nonverbal components of their voices to convey or exaggerate evolutionarily relevant traits in social contexts has scarcely been investigated. We already know from between-individual studies that nonverbal vocal parameters influence listeners’ judgments of the sex, age, body size, masculinity, dominance, competence, trustworthiness and attractiveness of different male and female speakers. Thus, we predict that within-individual modulation of these parameters could function to exploit listeners’ voice-based perceptual biases, potentially conferring social and reproductive benefits onto the speaker.

In this project, we examined the extent to which people volitionally or spontaneously modulate their voices across various social contexts, from dating to board meetings, and how this influences listeners’ biosocial judgments of speakers. Voice recordings were acoustically analyzed to quantify spectrotemporal parameters, and a variety of physical and demographic measures were taken from speakers and listeners (e.g. sex, age, body size, strength, hormones, ethnicity) to Identify factors affecting the production and perception of modulated speech. We additionally examined longitudinal variability in the voice across the lifetime and following major life events. To increase the generalisability of our results and address a serious need for cross-cultural sampling in the behavioural sciences, we recorded participants’ voices in controlled lab settings and real-world social contexts, and recruited men and women from Canada, China, Cuba, Finland, India, Poland, Tanzania, United Kingdom, United States of America.

In addition to providing new insight into the evolutionally functions and origins of nonverbal communication, this project is important for society because, as our results show, voice modulation is common in everyday social interactions and across diverse cultures, and can influence listeners' judgements and social decision making in personal and professional contexts.
This project has produced 5 peer-reviewed research articles (plus 5 under review), and 5 reviews/chapters (incl. Voice Modulation: A window into the origins of human vocal control? Trends in Cognitive Sciences, 20(4), 304-318.].

The results have been widely disseminated online (e.g. ResearchGate, Twitter, Facebook) through the media (BBC, CBC, Psychology Today, Telegraph, Time magazine, Men's Fitness), and in talks:

Research Conferences and Colloquia:
• Acoustical Societies of America/Japan (Honolulu USA)
• International Bioacoustics Council (Haridwar India)
• Polish Society for Human Evolution (Kraków Poland)
• British Psychological Association (Brighton UK)
• UK Research Office Symposium (Brighton UK)
• Sussex Psychology Colloquium
• Sussex Cognitive Brown Bag
Public Outreach Events:
• Royal Society Summer Science Exhibition (London UK)
• British Science Festival (Brighton UK)
• Get Psyched (Komedia Club, UK)
• BPS’s Weird Psychology (Brighton UK)

Study Summaries and Research Articles:

1. Longitudinal changes in the voice
In a longitudinal study of males aged 7-56, we show that voice pitch decreases during puberty, but remains remarkably stable throughout adulthood. Critically, pre-pubertal pitch predicts men’s pitch as adults, suggesting that within-individual differences in voice pitch that are known to play an important role in men’s reproductive success may be linked to prenatal androgen exposure.
• Published in Royal Society Open Science (doi:10.1098/rsos.160395)
In a follow-up study, we further show that the F0 of babies’ cries at 4 months of age predicts the F0 of their speech at 5 years of age.
• Under revision in Biology Letters
In a study tracking within-individual variation in mothers’ voices across 10 years, we show that mothers’ voices became significantly lower-pitched and more monotonous one year postpartum compared to during pregnancy or before, indicating that pregnancy has a transient and perceptually salient masculinizing effect on women’s voices.
• Under review in Proceedings of the Royal Society B

2. Spontaneous voice modulation across social contexts
To examine voice modulation in a real-life mating context, we recorded men and women in a speed-dating event. Both sexes lowered their voice pitch when interacting with desirable dates, supporting the hypothesis that voice modulation functions to elicit favourable judgments and behaviours from others, including potential mates. We also recorded men and women from UK, China, Finland, Poland, Slovakia and Tanzania (Hadza) in mocked social scenarios.
• Under revision in Evolution & Human Behavior

3. Volitional voice modulation for trait expression and exaggeration
In this study, we show that men and women from diverse countries spontaneously and systemically lower their voice pitch and vocal tract resonances to imitate a large body size. Men do so more than women. These results indicate potentially universal sound-size correspondences or anatomical and biomechanical constraints on voice modulation.
• Published in Scientific Reports (doi: 10.1038/srep34389) and Oxford Handbook of Voice Studies (in press).
With PhD student Jordan Raine, we show that nonverbal vocalisations (roars, screams, grunts) can convey critical cues (e.g. strength, pain intensity, contest outcome), supporting the hypothesis that human competitive vocalisations are homologous in form and function to those of other mammals.
• Published in Animal Behaviour (doi: 10.1016/j.anbehav.2017.06.02)
• Three additional articles under review.

4. Perceptual biases in voice perception
In a series of playback experiments we provide novel evidence for a multidimensional mapping of voice pitch to size and space, and, utilizing a large sample of blind and sighted adults, show that visual deprivation does not affect pitch-size correspondences, implicating a potential role of structurally-innate associations in pitch perception.
• Published in Attention, Perception & Psychophysics (doi: 10.3758/s13414-016-1273-6) and Cognition (doi: 10.1016/j.cognition.2018.02.023)
We anticipate 4-6 additional research articles from ongoing studies, the results of which will be presented at ISHE (Santiago Chile, 09.2018) and PTNCE (Warsaw Poland, 09.2018).

Impact and Implications of the Project:

Our results show that voice modulation, while rare in other animals, is commonly and cross-culturally observed in everyday social interactions among humans. The evolutionary origins of this complex form of vocal behaviour may be closely tied to the social advantages it appears to confer. The broad dissemination of these results to both the research and lay communities has increased awareness of the extent to which nonverbal vocal parameters can influence social stereotyping, highlighting that voice modulation can be used in some contexts to exaggerate or ‘fake’ one’s traits and capabilities, with potentially significant social, political and economic impacts.
Figure I. An illustration of voice frequency modulation