ALBERT

Description: A wealth of theoretical and empirical arguments have suggested that music triggers emotional responses by resembling the inflections of expressive vocalizations, but have done so using low-level acoustic parameters (pitch, loudness, speed) that, in fact, may not be processed by the listener in reference to human voice. Here, we take the opportunity of the recent availability of computational models that allow the simulation of three specifically vocal emotional behaviours: smiling, vocal tremor and vocal roughness. When applied to musical material, we find that these three acoustic manipulations trigger emotional perceptions that are remarkably similar to those observed on speech and scream sounds, and identical across musician and non-musician listeners. Strikingly, this not only applied to singing voice with and without musical background, but also to purely instrumental material. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.

Description: Vocal plasticity can occur in response to environmental and biological factors, including conspecifics' vocalizations and noise. Pinnipeds are one of the few mammalian groups capable of vocal learning, and are therefore relevant to understanding the evolution of vocal plasticity in humans and other animals. Here, we investigate the vocal plasticity of harbour seals ( Phoca vitulina ), a species with vocal learning abilities observed in adulthood but not puppyhood. To evaluate early mammalian vocal development, we tested 1–3 weeks-old seal pups. We tailored noise playbacks to this species and age to induce seal pups to shift their fundamental frequency ( f 0 ), rather than adapt call amplitude or temporal characteristics. We exposed individual pups to low- and high-intensity bandpass-filtered noise, which spanned—and masked—their typical range of f 0 ; simultaneously, we recorded pups' spontaneous calls. Unlike most mammals, pups modified their vocalizations by lowering their f 0 in response to increased noise. This modulation was precise and adapted to the particular experimental manipulation of the noise condition. In addition, higher levels of noise induced less dispersion around the mean f 0 , suggesting that pups may have actively focused their phonatory efforts to target lower frequencies. Noise did not seem to affect call amplitude. However, one seal showed two characteristics of the Lombard effect known for human speech in noise: significant increase in call amplitude and flattening of spectral tilt. Our relatively low noise levels may have favoured f 0 modulation while inhibiting amplitude adjustments. This lowering of f 0 is unusual, as most animals commonly display no such f 0 shift. Our data represent a relatively rare case in mammalian neonates, and have implications for the evolution of vocal plasticity and vocal learning across species, including humans. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.

Description: The human voice is a primary tool for verbal and nonverbal communication. Studies on laughter emphasize a distinction between spontaneous laughter, which reflects a genuinely felt emotion, and volitional laughter, associated with more intentional communicative acts. Listeners can reliably differentiate the two. It remains unclear, however, if they can detect authenticity in other vocalizations, and whether authenticity determines the affective and social impressions that we form about others. Here, 137 participants listened to laughs and cries that could be spontaneous or volitional and rated them on authenticity, valence, arousal, trustworthiness and dominance. Bayesian mixed models indicated that listeners detect authenticity similarly well in laughter and crying. Speakers were also perceived to be more trustworthy, and in a higher arousal state, when their laughs and cries were spontaneous. Moreover, spontaneous laughs were evaluated as more positive than volitional ones, and we found that the same acoustic features predicted perceived authenticity and trustworthiness in laughter: high pitch, spectral variability and less voicing. For crying, associations between acoustic features and ratings were less reliable. These findings indicate that emotional authenticity shapes affective and social trait inferences from voices, and that the ability to detect authenticity in vocalizations is not limited to laughter. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.

Description: Humans are vocal modulators par excellence. This ability is supported in part by the dual representation of the laryngeal muscles in the motor cortex. Movement, however, is not the product of motor cortex alone but of a broader motor network. This network consists of brain regions that contain somatotopic maps that parallel the organization in motor cortex. We therefore present a novel hypothesis that the dual laryngeal representation is repeated throughout the broader motor network. In support of the hypothesis, we review existing literature that demonstrates the existence of network-wide somatotopy and present initial evidence for the hypothesis' plausibility. Understanding how this uniquely human phenotype in motor cortex interacts with broader brain networks is an important step toward understanding how humans evolved the ability to speak. We further suggest that this system may provide a means to study how individual components of the nervous system evolved within the context of neuronal networks. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.

Description: The human voice carries information about a vocalizer's physical strength that listeners can perceive and that may influence mate choice and intrasexual competition. Yet, reliable acoustic correlates of strength in human speech remain unclear. Compared to speech, aggressive nonverbal vocalizations (roars) may function to maximize perceived strength, suggesting that their acoustic structure has been selected to communicate formidability, similar to the vocal threat displays of other animals. Here, we test this prediction in two non-WEIRD African samples: an urban community of Cameroonians and rural nomadic Hadza hunter–gatherers in the Tanzanian bushlands. Participants produced standardized speech and volitional roars and provided handgrip strength measures. Using acoustic analysis and information-theoretic multi-model inference and averaging techniques, we show that strength can be measured from both speech and roars, and as predicted, strength is more reliably gauged from roars than vowels, words or greetings. The acoustic structure of roars explains 40–70% of the variance in actual strength within adults of either sex. However, strength is predicted by multiple acoustic parameters whose combinations vary by sex, sample and vocal type. Thus, while roars may maximally signal strength, more research is needed to uncover consistent and likely interacting acoustic correlates of strength in the human voice. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.

Description: The human voice is dynamic, and people modulate their voices across different social interactions. This article presents a review of the literature examining natural vocal modulation in social contexts relevant to human mating and intrasexual competition. Altering acoustic parameters during speech, particularly pitch, in response to mating and competitive contexts can influence social perception and indicate certain qualities of the speaker. For instance, a lowered voice pitch is often used to exert dominance, display status and compete with rivals. Changes in voice can also serve as a salient medium for signalling a person's attraction to another, and there is evidence to support the notion that attraction and/or romantic interest can be distinguished through vocal tones alone. Individuals can purposely change their vocal behaviour in attempt to sound more attractive and to facilitate courtship success. Several findings also point to the effectiveness of vocal change as a mechanism for communicating relationship status. As future studies continue to explore vocal modulation in the arena of human mating, we will gain a better understanding of how and why vocal modulation varies across social contexts and its impact on receiver psychology. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.

Description: Research on within-individual modulation of vocal cues is surprisingly scarce outside of human speech. Yet, voice modulation serves diverse functions in human and nonhuman nonverbal communication, from dynamically signalling motivation and emotion, to exaggerating physical traits such as body size and masculinity, to enabling song and musicality. The diversity of anatomical, neural, cognitive and behavioural adaptations necessary for the production and perception of voice modulation make it a critical target for research on the origins and functions of acoustic communication. This diversity also implicates voice modulation in numerous disciplines and technological applications. In this two-part theme issue comprising 21 articles from leading and emerging international researchers, we highlight the multidisciplinary nature of the voice sciences. Every article addresses at least two, if not several, critical topics: (i) development and mechanisms driving vocal control and modulation; (ii) cultural and other environmental factors affecting voice modulation; (iii) evolutionary origins and adaptive functions of vocal control including cross-species comparisons; (iv) social functions and real-world consequences of voice modulation; and (v) state-of-the-art in multidisciplinary methodologies and technologies in voice modulation research. With this collection of works, we aim to facilitate cross-talk across disciplines to further stimulate the burgeoning field of voice modulation. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.

Description: Humans have a remarkable capacity to finely control the muscles of the larynx, via distinct patterns of cortical topography and innervation that may underpin our sophisticated vocal capabilities compared with non-human primates. Here, we investigated the behavioural and neural correlates of laryngeal control, and their relationship to vocal expertise, using an imitation task that required adjustments of larynx musculature during speech. Highly trained human singers and non-singer control participants modulated voice pitch and vocal tract length (VTL) to mimic auditory speech targets, while undergoing real-time anatomical scans of the vocal tract and functional scans of brain activity. Multivariate analyses of speech acoustics, larynx movements and brain activation data were used to quantify vocal modulation behaviour and to search for neural representations of the two modulated vocal parameters during the preparation and execution of speech. We found that singers showed more accurate task-relevant modulations of speech pitch and VTL (i.e. larynx height, as measured with vocal tract MRI) during speech imitation; this was accompanied by stronger representation of VTL within a region of the right somatosensory cortex. Our findings suggest a common neural basis for enhanced vocal control in speech and song. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.

Description: Voice modulatory cues such as variations in fundamental frequency, duration and pauses are key factors for structuring vocal signals in human speech and vocal communication in other tetrapods. Voice modulation physiology is highly similar in humans and other tetrapods due to shared ancestry and shared functional pressures for efficient communication. This has led to similarly structured vocalizations across humans and other tetrapods. Nonetheless, in their details, structural characteristics may vary across species and languages. Because data concerning voice modulation in non-human tetrapod vocal production and especially perception are relatively scarce compared to human vocal production and perception, this review focuses on voice modulatory cues used for speech segmentation across human languages, highlighting comparative data where available. Cues that are used similarly across many languages may help indicate which cues may result from physiological or basic cognitive constraints, and which cues may be employed more flexibly and are shaped by cultural evolution. This suggests promising candidates for future investigation of cues to structure in non-human tetrapod vocalizations. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.

Description: Music is universally prevalent in human society and is a salient component of the lives of young families. Here, we studied the frequency of singing and playing recorded music in the home using surveys of parents with infants ( N = 945). We found that most parents sing to their infant on a daily basis and the frequency of infant-directed singing is unrelated to parents’ income or ethnicity. Two reliable individual differences emerged, however: (i) fathers sing less than mothers and (ii) as infants grow older, parents sing less. Moreover, the latter effect of child age was specific to singing and was not reflected in reports of the frequency of playing recorded music. Last, we meta-analysed reports of the frequency of infant-directed singing and found little change in its frequency over the past 30 years, despite substantial changes in the technological environment in the home. These findings, consistent with theories of the psychological functions of music, in general, and infant-directed singing, in particular, demonstrate the everyday nature of music in infancy. This article is part of the theme issue ‘Voice modulation: from origin and mechanism to social impact (Part I)’.