David Reby

Jean Monnet University · Equipe de Neuro Ethologie Sensorielle

It is well established that in human speech perception the left hemisphere (LH) of the brain is specialized for processing intelligible phonemic (segmental) content (e.g., [1–3]), whereas the right hemisphere (RH) is more sensitive to pro-sodic (suprasegmental) cues [4, 5]. Despite evidence that a range of mammal species show LH specialization when...

An unresolved issue in comparative approaches to speech evolution is the apparent absence of an intermediate vocal communication system betweenhuman speech and the lessflexible vocal repertoires of other primates. We argue that humans’ ability to modulate nonverbal vocal features evolutionarily linked to expression of body size and sex (fundamental...

Recent studies have revealed that some mammals possess adaptations that enable them to produce vocal signals with much lower fundamental frequency (F0) and formant frequency spacing (DF) than expected for their size. Although these adaptations are assumed to reflect selection pressures for males to lower frequency components and exaggerate body siz...

Why do distantly related mammals like sheep, giant pandas, and fur seals produce bleats that are characterized by vibrato-like fundamental frequency (F0) modulation? To answer this question, we used psychoacoustic tests and comparative analyses to investigate whether this distinctive vocal feature has evolved to improve the perception of formants,...

How can deceptive communication signals exist in an evolutionarily stable signalling system? To resolve this age-old honest signalling paradox, researchers must first establish whether deception benefits deceivers. However, while vocal exaggeration is widespread in the animal kingdom and assumably adaptive, its effectiveness in biasing listeners ha...

Acoustic signals are key components of animal social behaviour, potentially conveying fitness relevant information about signallers. Howler monkeys produce extremely loud, low frequency roars, which exaggerate the acoustic impression of body size relative to other species. However, it remains unclear whether howler monkey roars contain reliable inf...

Avian begging calls mediate parent–offspring conflict and direct parental care to genetically related progeny. We found that the fundamental frequency of begging calls of African Penguins Spheniscus demersus decreases as the penguins age and gain mass, before reaching a lower plateau when the chick reaches about 1 kg. Our results suggest that the f...

Crop damage and vehicle collisions caused by wild ungulates require effective deterrents. Many commercial acoustic devices use ultrasonic signals, presenting them as aversive to these animals. However, unconvincing results reported in previous studies using (non-frequency modulated) ultrasounds bring their effectiveness as deterrent signals into qu...

Human nonverbal vocalizations such as screams and cries often reflect their evolved functions. Although the universality of these putatively primordial vocal signals and their phylogenetic roots in animal calls suggest a strong reflexive foundation, many of the emotional vocalizations that we humans produce are under our voluntary control. This sug...

At some point in our evolutionary history, humans lost vocal membranes and air sacs, representing an unexpected simplification of the vocal apparatus relative to other apes. One hypothesis is that these simplifications represent anatomical adaptations for speech because a simpler larynx provides a suitably stable and tonal vocal source with fewer n...

Baby cries can convey both static information related to individual identity and dynamic information related to the baby’s emotional and physiological state. How do these dimensions interact? Are they transmitted independently, or do they compete against one another? Here we show that the universal acoustic expression of pain in distress cries over...

Formants (vocal tract resonances) are increasingly analyzed not only by phoneticians in speech but also by behavioral scientists studying diverse phenomena such as acoustic size exaggeration and articulatory abilities of non-human animals. This often involves estimating vocal tract length acoustically and producing scale-invariant representations o...

Across many species, a major function of vocal communication is to convey formidability, with low voice frequencies traditionally considered the main vehicle for projecting large size and aggression. Vocal loudness is often ignored, yet it might explain some puzzling exceptions to this frequency code. Here we demonstrate, through acoustic analyses...

Variation in formant frequencies has been shown to affect social interactions and sexual competition in a range of avian species. Yet, the anatomical bases of this variation are poorly understood. Here, we investigated the morphological correlates of formants production in the vocal apparatus of African penguins. We modelled the geometry of the sup...

What information is encoded in the cries of human babies? While it is widely recognized that cries can encode distress levels, whether cries reliably encode the cause of crying remains disputed. Here, we collected 39201 cries from 24 babies recorded in their homes longitudinally, from 15 days to 3.5 months of age, a database we share publicly for r...

Humans have evolved voluntary control over vocal production for speaking and singing, while preserving the phylogenetically older system of spontaneous nonverbal vocalizations such as laughs and screams. To test for systematic acoustic differences between these vocal domains, we analyzed a broad, cross-cultural corpus representing over 2 h of speec...

Global biodiversity is in rapid decline, and many seabird species have disproportionally poorer conservation statuses than terrestrial birds. A good understanding of population dynamics is necessary for successful conservation efforts, making noninvasive, cost-effective monitoring tools essential. Here, we set out to investigate whether passive aco...

Pet-directed speech (PDS) is often produced by humans when addressing dogs. Similar to infant-directed speech, PDS is marked by a relatively higher and more modulated fundamental frequency ( f 0 ) than is adult-directed speech. We tested the prediction that increasing eye size in dogs, one facial feature of neoteny (juvenilisation), would elicit ex...

The ability to discriminate between different individuals based on identity cues, which is important to support the social behaviour of many animal species, has mostly been investigated in conspecific contexts. A rare example of individual heterospecific discrimination is found in domestic dogs, who are capable of recognising their owners’ voices....

Because the expression of pain in babies’ cries is based on universal acoustic features, it is assumed that adult listeners should be able to detect when a crying baby is experiencing pain1, 2, 3. We report that detecting that a baby’s cry expresses pain actually requires learning through experience. Our psychoacoustic experiments reveal that adult...

While nonlinear phenomena (NLP) are widely reported in animal vocalizations, often causing perceptual harshness and roughness, their communicative function remains debated. Several hypotheses have been put forward: attention-grabbing, communication of distress, exaggeration of body size and dominance. Here, we use state-of-the-art sound synthesis t...

Animals normally vocalise while exhaling. Ingressive, or inspiratory, voice production occurs in humans and many other species, but its communicative function, if any, remains unknown. To test the perceptual effects of ingressive phonation, naturally occurring ingressive syllables in 109 human nonverbal vocalisations (55 laughs, 21 cries, and 33 mo...

Humans possess intuitive associations linking certain non-redundant features of stimuli—e.g. high-pitched sounds with small object size (or similarly, low -pitched sounds with large object size). This phenomenon, known as crossmodal correspondence, has been identified in humans across multiple different senses. There is some evidence that non-human...

Until recently, human nonverbal vocalisations such as cries, laughs, screams, moans, and groans have received relatively little attention in the human behavioural sciences. Yet these vocal signals are ubiquitous in human social interactions across diverse cultures and may represent a missing link between relatively fixed nonhuman animal vocalisatio...

Overcoming gender occupational stereotypes is a major educational objective in removing barriers to children's future career ambitions and employment aspirations. Yet, the mechanisms that underlie the development of occupational stereotypes in school-age children remain unclear. This questionnaire study investigates the developmental relationship b...

When producing intimidating aggressive vocalizations, humans and other animals often extend their vocal tracts to lower their voice resonance frequencies (formants) and thus sound big. Is acoustic size exaggeration more effective when the vocal tract is extended before, or during, the vocalization, and how do listeners interpret within-call changes...

Existing evidence suggests that children from around the age of 8 years strategically alter their public image in accordance with known values and preferences of peers, through the self-descriptive information they convey. However, an important but neglected aspect of this ‘self-presentation’ is the medium through which such information is communic...

Vocal tract elongation, which uniformly lowers vocal tract resonances (formant frequencies) in animal vocalizations, has evolved independently in several vertebrate groups as a means for vocalizers to exaggerate their apparent body size. Here, we propose that smaller speech-like articulatory movements that alter only individual formants can serve a...

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. T...

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...

This document contains all code, and step by step explanations for all analyses, figures and tables (including supplementary figures and tables) for: Kleisner K et al. 2021 Predicting strength from aggressive vocalizations versus speech in African bushland and urban communities. Phil. Trans. R. Soc. B 376, 20200403. (doi:10.1098/rstb.2020.0403). Da...

Distress cries are emitted by many mammal species to elicit caregiving attention. Across taxa, these calls tend to share similar acoustic structures, but not necessarily frequency range, raising the question of their interspecific communicative potential. As domestic dogs are highly responsive to human emotional cues and experience stress when hear...

Quantifying the intensity of animals’ reaction to stimuli is notoriously difficult as classic unidimensional measures of responses such as latency or duration of looking can fail to capture the overall strength of behavioural responses. More holistic rating can be useful but have the inherent risks of subjective bias and lack of repeatability. Here...

Eurasian deer are characterized by the extraordinary diversity of their vocal repertoires. Male sexual calls range from roars with relatively low fundamental frequency (hereafter fo) in red deer Cervus elaphus, to moans with extremely high fo in sika deer Cervus nippon, and almost infrasonic groans with exceptionally low fo in fallow deer Dama dama...

A lion's roar, a dog's bark, an angry yell in a pub brawl: what do these vocalizations have in common? They all sound harsh due to nonlinear vocal phenomena (NLP)—deviations from regular voice production, hypothesized to lower perceived voice pitch and thereby exaggerate the apparent body size of the vocalizer. To test this yet uncorroborated hypot...

African Penguins (Spheniscus demersus) are endangered and declining seabirds which make extensive use of vocal signals for intra‐specific vocal communication. Accordingly, passive acoustic monitoring tools could be developed as robust population monitoring methods that cause minimal disturbance to the birds. In this study, we collected soundscape r...

The adult voice is a strong bio-social marker for masculinity and femininity. In this study we investigated whether children make gender stereotypical judgments about adults’ occupational competence on the basis of their voice. Forty-eight 8- to 10- year olds were asked to rate the competence of adult voices that varied in vocal masculinity (by art...

Nonlinear vocal phenomena (NLPs) are commonly reported in animal calls and, increasingly, in human vocalizations. These perceptually harsh and chaotic voice features function to attract attention and convey urgency, but they may also signal aversive states. To test whether NLPs enhance the perception of negative affect or only signal high arousal,...

Context-related information can be reflected within mammalian vocalisations and could in turn be studied to benefit production animals. Whilst previous research has revealed the contextual, and even emotional content of goat, pig and horse vocalisations, cattle vocalisations remain relatively less explored. In this study we recorded the vocalisatio...

In this study, we explored the use of variation in sex-related cues of the voice to investigate implicit occupational stereotyping in children. Eighty-two children between the ages of 5 and 10 years took part in an imitation task in which they were provided with descriptions of nine occupations (three traditionally male, three traditionally female,...

Understanding how information is encoded in vocal signals, and what function it serves during social and sexual interactions, is a key objective of animal communication research. In this chapter, we focus on the origins and functions of vocal cues to stable, long-term attributes of callers (such as identity, sex, and body size) in terrestrial mamma...

Fundamental frequency (F0, perceived as voice pitch) predicts sex and age, hormonal status, mating success and a range of social traits, and thus functions as an important biosocial marker in modal speech. Yet, the role of F0 in human nonverbal vocalizations remains unclear, and given considerable variability in F0 across call types, it is not know...

Neurobiological changes affecting new mothers are known to support the development of the mother-infant relationship (the 'maternal brain'). However, which aspects of parenting are actually mother-specific and which rely on general cognitive abilities remains debated. For example, refuting earlier findings, a recent study demonstrated that fathers...

Information compression is a general principle of human language: the most frequent words are shorter in length (Zipf's Law of Brevity) and the duration of constituents decreases as the size of the linguistic construct increases (Menzerath-Altmann Law). Vocal sequences of non-human primates have been shown to conform to both these laws, suggesting...

Cattle mother-offspring contact calls encode individual-identity information; however, it is unknown whether cattle are able to maintain individuality when vocalising to familiar conspecifics over other positively and negatively valenced farming contexts. Accordingly, we recorded 333 high-frequency vocalisations from 13 Holstein-Friesian heifers du...

Domesticated animals have been shown to recognize basic phonemic information from human speech sounds and to recognize familiar speakers from their voices. However, whether animals can spontaneously identify words across unfamiliar speakers (speaker normalization) or spontaneously discriminate between unfamiliar speakers across words remains to be...

Crossmodal correspondences are intuitively held relationships between non-redundant features of a stimulus, such as auditory pitch and visual illumination. While a number of correspondences have been identified in humans to date (e.g. high pitch is intuitively felt to be luminant, angular and elevated in space), their evolutionary and developmental...

Low frequency components (i.e. a low pitch (F0) and low formant spacing (ΔF)) signal high salivary testosterone and height in adult male voices and are associated with high masculinity attributions by unfamiliar listeners (in both men and women). However, the relation between the physiological, acoustic and perceptual dimensions of speakers' mascul...

Pre-pubertal boys and girls speak with acoustically different voices despite the absence of a clear anatomical dimorphism in the vocal apparatus, suggesting that a strong component of the expression of gender through the voice is behavioural. Initial evidence for this hypothesis was found in a previous study showing that they can alter their voice...

Despite widespread evidence that nonverbal components of human speech (e.g., voice pitch) communicate information about physical attributes of vocalizers and that listeners can judge traits such as strength and body size from speech, few studies have examined the communicative functions of human nonverbal vocalizations (such as roars, screams, grun...

Full protocol of acoustic analysis. (DOCX)

Supplementary tables. (DOCX)

Significant zero-order correlations. (DOCX)

In the absence of clear sex differences in vocal anatomy, the expression of gender in pre‐pubertal children's voices has a strong behavioural dimension. However, whether children are sensitive to this gender‐related variation in the voice and use it to make inferences about their peers’ masculinity and femininity remains unexplored. Using a cross‐m...

Inter-individual differences in human fundamental frequency (F0, perceived as voice pitch) predict mate quality and reproductive success, and affect lis-teners' social attributions. Although humans can readily and volitionally manipulate their vocal apparatus and resultant voice pitch, for instance, in the production of speech sounds and singing, l...

Voice pitch (fundamental frequency, F0) is a key dimension of our voice that varies between sexes after puberty, and also among individuals of the same sex both before and after puberty. While a recent longitudinal study indicates that inter-individual differences in voice pitch remain stable in men during adulthood and may even be determined befor...

While evidence suggests that pain cries produced by human babies and other mammal infants communicate pain intensity, whether the pain vocalisations of human adults also encode pain intensity, and which acoustic characteristics influence listeners’ perceptions, remains unexplored. Here, we investigated how trained actors communicated pain by compar...

Data S3. Audio Exemplars of Roars and Speech from Three Males and Three Females, Related to Tables 1 and 2, and Figures 1 and 2

Males of several species of deer have a descended and mobile larynx, resulting in an unusually long vocal tract, which can be further extended by lowering the larynx during call production. Formant frequencies are lowered as the vocal tract is extended, as predicted when approximating the vocal tract as a uniform quarter wavelength resonator. Howev...

Although animal vocalizations and human speech are known to communicate physical formidability, no previous study has examined whether human listeners can assess the strength or body size of vocalizers relative to their own, either from speech or from nonverbal vocalizations. Here, although men tended to underestimate women's formidability, and wom...

Women's voice pitch (the perceptual correlate of fundamental frequency, F0) varies across the menstrual cycle and lowers after menopause, and may represent a putative signal of women's fertility and reproductive age. Yet, despite dramatic changes in women's sex hormone levels and bodies during and after pregnancy, previous between-subject and case...

Cross-modal correspondences describe the widespread tendency for attributes in one sensory modality to be consistently matched to those in another modality. For example, high pitched sounds tend to be matched to spiky shapes, small sizes, and high elevations. However, the extent to which these correspondences depend on sensory experience (e.g. regu...

Koalas are characterised by a highly unusual vocal anatomy, with a descended larynx and velar vocal folds, allowing them to produce calls at disproportionately low frequencies. Here we use advanced imaging techniques, histological data, classical macroscopic dissection and behavioural observations to provide the first detailed description and inter...

Despite their ubiquity in human behaviour, the communicative functions of nonverbal vocalizations remain poorly understood. Here, we analysed the acoustic structure of tennis grunts, nonverbal vocalizations produced in a competitive context. We predicted that tennis grunts convey information about the vocalizer and context, similar to nonhuman voca...

Crying is a vital built-in survival mechanism for the human baby. Yet both the information carried by cries and the factors driving the perception and reaction of adult listeners remain under-investigated. Here, we contrasted the relevance of psycho-acoustic vs. acoustic evaluation for the assessment of distress levels in babies’ cries recorded dur...

There is a widespread tendency to associate certain properties of sound with those of colour (e.g., higher pitches with lighter colours). Yet it is an open question how sound influences chroma or hue when properly controlling for lightness. To examine this, we asked participants to adjust physically equiluminant colours until they 'went best' with...

Trumpet calls are very loud voiced signals given by highly aroused elephants, and appear to be produced by a forceful expulsion of air through the trunk. Beyond their characteristic “brassy quality” previously attributed to shockwave formation, some trumpet calls are also characterized by stepwise fundamental frequency increase and decrease. Here w...

Understanding the extent to which humans perceive the emotional state of animals has both theoretical and practical implications. While recent studies indicate that natural selection has led to some convergence of emotion coding among vertebrate species (including humans), highlighting the interspecific value of emotional signals, it has also been...

Pet-directed speech is strikingly similar to infant-directed speech, a peculiar speaking pattern with higher pitch and slower tempo known to engage infants' attention and promote language learning. Here, we report the first investigation of potential factors modulating the use of dog-directed speech, as well as its immediate impact on dogs' behavio...