Vocal Flexibility Research Articles

Morphologically structured vocalizations in female Diana monkeys

Social complexity is often thought of as a driving force in the evolution of communication and cognition, but this is at odds with the fact that nonhuman primates generally display only very limited flexibility in vocal production. Some primates partially overcome their limited vocal flexibility by combining two or more acoustically inflexible calls into complex sequences. Equally relevant is that some primate calls consist of separable morphological elements whose combinations create different meanings. Here, we focus on the vocal system of wild female Diana monkeys, Cercopithecus diana, which produce three call units (R, L, A) either singly or merged as RA or LA call combinations. Previous work has shown that R and L convey information about external events, while A conveys information about caller identity. We tested this hypothesis experimentally, by broadcasting artificially combined utterances to eight adult females. To test the significance of the R and L ‘event’ units, we merged them with the A ‘identity’ unit of a group member. To test the significance of the ‘identity’ unit, we merged an R ‘event’ unit with an ‘identity’ unit from a group member or a neighbouring individual. Subjects responded in ways that suggested that both event and identity units were relevant, suggesting that Diana monkeys’ social calls possess morphosemantic features. We discuss this finding in relation to the coevolution of communication and social complexity in primates.

Voicing the real Self

Voicing the real Self

Vocal flexibility and regional variation in free-tailed bat songs

Male Brazilian free tailed bats (Tadarida brasiliensis), sing to attract females and defend territories during the mating season. These songs are unusual among mammalian vocalizations in that they are highly complex and hierarchically structured. Songs are composed of multiple syllables which are combined into three phrases that vary in number and order across renditions. While much work has been done on regional vocal variation in birds, relatively a few studies have found similar evidence in mammals. This study aimed to determine if T. brasiliensis songs vary across agographical regions. To accomplish this, we compared spectro-temporal characteristics, and phrase composition of songs recorded from wild colonies in various locations throughout Florida, Georgia, and Texas. Although we found considerable inter-individual and within-individual variation, there are salient regional differences in song structure. These findings combined with a high level of within-individual flexibility, and the lack of local adaptation in foraging echolocation pulses, support a possible role of vocal learning in song production in this species.

A Mozart is not a Pavarotti: singers outperform instrumentalists on foreign accent imitation.

Recent findings have shown that people with higher musical aptitude were also better in oral language imitation tasks. However, whether singing capacity and instrument playing contribute differently to the imitation of speech has been ignored so far. Research has just recently started to understand that instrumentalists develop quite distinct skills when compared to vocalists. In the same vein the role of the vocal motor system in language acquisition processes has poorly been investigated as most investigations (neurobiological and behavioral) favor to examine speech perception. We set out to test whether the vocal motor system can influence an ability to learn, produce and perceive new languages by contrasting instrumentalists and vocalists. Therefore, we investigated 96 participants, 27 instrumentalists, 33 vocalists and 36 non-musicians/non-singers. They were tested for their abilities to imitate foreign speech: unknown language (Hindi), second language (English) and their musical aptitude. Results revealed that both instrumentalists and vocalists have a higher ability to imitate unintelligible speech and foreign accents than non-musicians/non-singers. Within the musician group, vocalists outperformed instrumentalists significantly. Conclusion: First, adaptive plasticity for speech imitation is not reliant on audition alone but also on vocal-motor induced processes. Second, vocal flexibility of singers goes together with higher speech imitation aptitude. Third, vocal motor training, as of singers, may speed up foreign language acquisition processes.

White-throated sparrows alter songs differentially in response to chorusing anurans and other background noise

Animals can use acoustic signals to attract mates and defend territories. As a consequence, background noise that interferes with signal transmission has the potential to reduce fitness, especially in birds that rely on song. While much research on bird song has investigated vocal flexibility in response to urban noise, weather and other birds, the possibility of inter-class acoustic competition from anurans has not been previously studied. Using sound recordings from central Ontario wetlands, we tested if white-throated sparrows (Zonotrichia albicolis) make short-term changes to their singing behaviour in response to chorusing spring peepers (Pseudacris crucifer), as well as to car noise, wind and other bird vocalizations. White-throated sparrow songs that were sung during the spring peeper chorus were shorter with higher minimum frequencies and narrower bandwidths resulting in reduced frequency overlap. Additionally, sparrows were less likely to sing when car noise and the vocalizations of other birds were present. These patterns suggest that birds use multiple adjustment strategies. This is the first report to demonstrate that birds may alter their songs differentially in response to different sources of noise.This article is part of a Special Issue entitled: insert SI title.

Possible role of mother-daughter vocal interactions on the development of species-specific song in gibbons.

Mother-infant vocal interactions play a crucial role in the development of human language. However, comparatively little is known about the maternal role during vocal development in nonhuman primates. Here, we report the first evidence of mother-daughter vocal interactions contributing to vocal development in gibbons, a singing and monogamous ape species. Gibbons are well known for their species-specific duets sung between mates, yet little is known about the role of intergenerational duets in gibbon song development. We observed singing interactions between free-ranging mothers and their sub-adult daughters prior to emigration. Daughters sang simultaneously with their mothers at different rates. First, we observed significant acoustic variation between daughters. Co-singing rates between mother and daughter were negatively correlated with the temporal precision of the song’s synchronization. In addition, songs of daughters who co-sang less with their mothers were acoustically more similar to the maternal song than any other adult female’s song. All variables have been reported to be influenced by social relationships of pairs. Therefore those correlations would be mediated by mother-daughter social relationship, which would be modifiable in daughter’s development. Here we hypothesized that daughters who co-sing less often, well-synchronize, and converge acoustically with the maternal acoustic pattern would be at a more advanced stage of social independence in sub-adult females prior to emigration. Second, we observed acoustic matching between mothers and daughters when co-singing, suggesting short-term vocal flexibility. Third, we found that mothers adjusted songs to a more stereotyped pattern when co-singing than when singing alone. This vocal adjustment was stronger for mothers with daughters who co-sang less. These results indicate the presence of socially mediated vocal flexibility in gibbon sub-adults and adults, and that mother-daughter co-singing interactions may enhance vocal development. More comparative work, notably longitudinal and experimental, is now needed to clarify maternal roles during song development.

Vocal Flexibility and Prosodic Strategies in a Professional Impersonator

Voice imitation of a famous personality results in detection and reproduction of some vocal features, including spectral characteristics but also prosody, speech flow, or articulatory patterns. The objective of this study was to describe vocal flexibility in one of the best French impersonators and determine his strategies. Prospective study. We have downloaded the recording of a political speech by former French President Jacques Chirac, who we have chosen for his very specific and recognizable voice. After transcription, we asked one professional impersonator and four control subjects to do several readings in their natural voice and in a spontaneous imitation task (ie, without listening to any of Chirac's recording). To facilitate the control subject's task, we made an additional recording after having them listen to the target sample. Using Praat freeware, we have compared several prosodic measurements taken on each sample: pitch, pitch range, articulatory speed, duration of pauses, and number of pauses. Results showed significant modifications in the participant's prosody and significant differences in the strategies used by the professional impersonator and the control group. The professional impersonator's imitation strategy lies in the reproduction of global characteristics and instant alignment of prosodic variations.

Vocal modifications in primates: Effects of noise and behavioral context on vocalization structure.

During increased noise, modifications of the acoustic structure of vocalizations (amplitude, temporal, and spectral parameters) may allow release from masking, potentially conferring fitness benefits to vocally flexible signalers. Among primates, humans have demonstrated extreme vocal flexibility during noise, with modifications to all three speech parameters affected by both noise type and motivational state of the signaler. While non-human primates have also demonstrated changes to call amplitude and temporal characteristics, to the best of our knowledge spectral modifications have not been observed and the influence of behavioral context remains unknown. This experiment used playbacks of broad (10 kHz) and narrowband (5 kHz) white noise to investigate the effects of noise level and bandwidth on chirps and combination long calls (CLCs) produced by cotton-top tamarins (Saguinus oedipus). Noise amplitude and frequency content both influenced the structure of vocalizations; modifications included increased call amplitude (the Lombard effect), changes to call durations, and previously undocumented spectral shifts. Behavioral context was also relevant; modifications to CLCs were different from those observed in chirps. These results provide the first evidence of noise-induced spectral shifts in non-human primates, and emphasize the importance of behavioral context in vocal noise compensation.

Flexible alarm calling in meerkats: the role of the social environment and predation urgency

Flexible vocal production has been demonstrated in several vertebrate species, with much work focusing on the role of the social “audience” in explaining variation in call production. It is, however, likely that the decision to call is an emergent property of both external and internal factors, and the extent to which these factors are integrated has been little investigated. We addressed this question by examining the production of alarm calls in wild male meerkats (Suricata suricatta) in different social environments and different predator-encounter contexts. Males searching for reproductive opportunities (rovers) were followed 1) in their home group and when prospecting either 2) solitarily or 3) in a coalition with other males. Results showed that conspecific presence influenced the production of flee-alarm and recruitment calls. Solitary rovers were less likely to produce flee-alarm calls compared with when they are with conspecifics, whether coalitionary rovers or the rover’s home group. Experimentally elicited recruitment calls were also produced less when males were solitary than when in their home group. Bark vocalizations, emitted when meerkats were safe, were always produced irrespective of conspecific presence, indicating that these calls function to address predators. The probability of producing flee alarms also increased with the urgency of the predation event. Our results indicate that variation in alarm call production depends on whom the call is addressed to and also on the motivational state of the caller. We argue that neglecting to integrate internal and external factors when elucidating mechanisms underlying vocal production can potentially lead to misguided, parsimonious conclusions regarding vocal flexibility in animals.

Flexibility in Animal Signals Facilitates Adaptation to Rapidly Changing Environments

Charles Darwin posited that secondary sexual characteristics result from competition to attract mates. In male songbirds, specialized vocalizations represent secondary sexual characteristics of particular importance because females prefer songs at specific frequencies, amplitudes, and duration. For birds living in human-dominated landscapes, historic selection for song characteristics that convey fitness may compete with novel selective pressures from anthropogenic noise. Here we show that black-capped chickadees (Poecile atricapillus) use shorter, higher-frequency songs when traffic noise is high, and longer, lower-frequency songs when noise abates. We suggest that chickadees balance opposing selective pressures by use low-frequency songs to preserve vocal characteristics of dominance that repel competitors and attract females, and high frequency songs to increase song transmission when their environment is noisy. The remarkable vocal flexibility exhibited by chickadees may be one reason that they thrive in urban environments, and such flexibility may also support subsequent genetic adaptation to an increasingly urbanized world.

Context-related call combinations in female Diana monkeys

Non-human primates possess species-specific repertoires of acoustically distinct call types that can be found in adults in predictable ways. Evidence for vocal flexibility is generally rare and typically restricted to acoustic variants within the main call types or sequential production of multiple calls. So far, evidence for context-specific call sequences has been mainly in relation to external disturbances, particularly predation. In this study, we investigated extensively the vocal behaviour of free-ranging and individually identified Diana monkeys in non-predatory contexts. We found that adult females produced four vocal structures alone ('H', 'L', 'R' and 'A' calls, the latter consisting of two subtypes) or combined in non-random ways ('HA', 'LA' and 'RA' call combinations) in relation to ongoing behaviour or external events. Specifically, the concatenation of an introductory call with the most frequently emitted and contextually neutral 'A' call seems to function as a contextual refiner of this potential individual identifier. Our results demonstrate that some non-human primates are able to increase the effective size of their small vocal repertoire not only by varying the acoustic structure of basic call types but also by combining them into more complex structures. We have demonstrated this phenomenon for a category of vocalisations with a purely social function and discuss the implications of these findings for evolutionary theories of primate vocal communication.

Social learning of vocal structure in a nonhuman primate?

BackgroundNon-human primate communication is thought to be fundamentally different from human speech, mainly due to vast differences in vocal control. The lack of these abilities in non-human primates is especially striking if compared to some marine mammals and bird species, which has generated somewhat of an evolutionary conundrum. What are the biological roots and underlying evolutionary pressures of the human ability to voluntarily control sound production and learn the vocal utterances of others? One hypothesis is that this capacity has evolved gradually in humans from an ancestral stage that resembled the vocal behavior of modern primates. Support for this has come from studies that have documented limited vocal flexibility and convergence in different primate species, typically in calls used during social interactions. The mechanisms underlying these patterns, however, are currently unknown. Specifically, it has been difficult to rule out explanations based on genetic relatedness, suggesting that such vocal flexibility may not be the result of social learning.ResultsTo address this point, we compared the degree of acoustic similarity of contact calls in free-ranging Campbell's monkeys as a function of their social bonds and genetic relatedness. We calculated three different indices to compare the similarities between the calls' frequency contours, the duration of grooming interactions and the microsatellite-based genetic relatedness between partners. We found a significantly positive relation between bond strength and acoustic similarity that was independent of genetic relatedness.ConclusionGenetic factors determine the general species-specific call repertoire of a primate species, while social factors can influence the fine structure of some the call types. The finding is in line with the more general hypothesis that human speech has evolved gradually from earlier primate-like vocal communication.

Vocal frequency change reflects different responses to anthropogenic noise in two suboscine tyrant flycatchers

Anthropogenic noise is prevalent across the globe and can exclude birds from otherwise suitable habitat and negatively influence fitness; however, the mechanisms responsible for species' responses to noise are not always clear. One effect of noise is a reduction in effective acoustic communication through acoustic masking, yet some urban songbirds may compensate for masking by noise through altering their songs. Whether this vocal flexibility accounts for species persistence in noisy areas is unknown. Here, we investigated the influence of noise on habitat use and vocal frequency in two suboscine flycatchers using a natural experiment that isolated effects of noise from confounding stimuli common to urban habitats. With increased noise exposure, grey flycatcher (Empidonax wrightii) occupancy declined, but vocal frequency did not change. By contrast, ash-throated flycatcher (Myiarchus cinerascens) occupancy was uninfluenced by noise, but individuals in areas with greater noise amplitudes vocalized at a higher frequency, although the increase (≈200 kHz) may only marginally improve communication and may represent a secondary effect from increased vocal amplitude. Even so, the different flycatcher behavioural responses suggest that signal change may help some species persist in noisy areas and prompt important questions regarding which species will cope with an increasingly noisy world.

Locução em Propagandas: Uma Releitura da Caracterização de Vozes Profissionais

A voz humana está presente na maioria das propagandas, publicidades e comerciais veiculados em rádio e televisão. Este artigo apresenta uma caracterização vocal de gravações de locuções profissionais nessas áreas. A análise aborda aspectos de psicodinâmica vocal relacionados aos principais tipos de vozes e parâmetros vocais identificados, comenta as implicações dessas opções vocais na saúde vocal do locutor e estabelece relações com as necessidades atuais da interpretação vocal na locução.

Genes & cells: Gene implicated in speech evolution: Duplicated DNA aided vocal cord flexibility, study suggests

Genes & cells: Gene implicated in speech evolution: Duplicated DNA aided vocal cord flexibility, study suggests

Team Management of Voice Disorders in Singers

Team Management of Voice Disorders in Singers

Investigating noise effects on the call amplitude of endangered Southern Resident killer whales (Orcinus orca)

Anthropogenic sound exposure has been identified as a potential threat to endangered Southern Resident killer whales (SRKWs). Such exposure can mask important biological sounds including those used for social functions. Vocal animals might compensate for increased background noise by calling louder (the Lombard effect). In this study, amplitude compensation was investigated in SRKW communication calls recorded off of San Juan Island, WA, U.S.A. Data were obtained from two calibrated recording systems, a shore-based hydrophone array [V. Veirs, J. Acoust. Soc. Am., 116, 2615 (2004)] and a boat-based vertical array. Calls were localized using time of arrival differences to estimate range and apparent source levels after background levels were subtracted from the signal. Call levels were calculated assuming spreading loss functions determined from sound propagation observations made in situ. Results demonstrated a positive relationship between call levels and background levels. Costs of such vocal flexibility are unknown, but may include changes in energetic demand and/or communicative functionality. Within the data ranges measured in this study, killer whales communicatively adjusted for fluctuating background noise levels. However, other sounds detected during passive listening (e.g. prey sounds) might be more susceptible to masking effects [Work supported by NOAA and Colorado College.]

Cricothyroid subluxation: a new innovation for enhancing the voice with laryngoplastic phonosurgery.

Laryngoplastic phonosurgery has evolved to become a dominant treatment modality for paralytic dysphonia. Current surgical procedures have addressed primarily the position of the musculomembranous vocal fold and the arytenoid in the axial and vertical planes. However. dynamic range capabilities and vocal flexibility have been limited secondary to the flaccid, denervated vocal fold tissue. Therefore. a new procedure was conceived to enhance the acoustic vocal outcome from operations that reposition the vocal edge. Cricothyroid (CT) subluxation was designed as a technique to increase the distance between the cricoarytenoid joint and the insertion of the anterior commissure ligament. Cricothyroid subluxation was done without complication in 9 patients who underwent combined adduction arytenopexy and medialization laryngoplasty, and in 4 patients with medialization laryngoplasty alone. Postoperative stroboscopic assessment was done in all of the 13 patients, while complete analysis of vocal function was available in 10 of the 13 patients; this revealed improvement (as a group) on almost all objective measures over the preoperative state. All patients who underwent CT subluxation had a normal maximum frequency range (pitch variation of more than 2 octaves), as compared with 22% of a prior similar cohort of patients who did not undergo CT subluxation. All patients who underwent CT subluxation had normal glottal airflow and a normal noise-to-harmonics ratio. Cricothyroid subluxation is a relatively easily adjustable procedure that increases the length and viscoelastic tension of the denervated vocal fold. The modified biomechanical properties resulted in improved vocal outcome in all of our patients, which was most remarkable in terms of maximal range capabilities. Cricothyroid subluxation enhanced the postoperative voice of patients regardless of whether they required medialization laryngoplasty alone or whether they also required adduction arytenopexy.

Adduction arytenopexy with medialization laryngoplasty and cricothyroid subluxation: A new approach to paralytic dysphonia

Laryngoplastic phonosurgery has evolved into a dominant treatment modality for paralytic dysphonia. Current surgical procedures have primarily addressed the position of the vocal fold in the axial and vertical planes. However, dynamic range capabilities and vocal flexibility have been limited secondary to the flaccid, dennervated vocal-fold tissue. Two new procedures were designed to optimally position the arytenoid and to restore tension in the dennervated vocal fold. The new adduction arytenopexy procedure more closely models the biomechanics underlying normal cricoarytenoid adduction than the classical arytenoid adduction does. This procedure allows for gliding, rocking, and rotating of the arytenoid on the cricoid facet, thereby simulating simultaneous agonist-antagonist function of the interarytenoid, lateral cricoarytenoid, and posterior cricoarytenoid muscles. Cricothyroid subluxation (C-T sub) was designed as a technique to increase the distance between the cricoarytenoid joint and the insertion of the anterior commissure ligament. This led to an increase in length and tension of the thyroarytenoid musculature so that there is improved dynamic frequency range of the voice. C-T sub enhanced the postoperative voice of patients, regardless of whether they required medialization laryngoplasty alone or with adduction arytenopexy.

Out of the mouths of babes . . . and beaks of birds? A broader interpretation of the frame/content theory for the evolution of speech production

Much of the material MacNeilage cites to support his frame/content theory for the evolution of speech production in humans is not unique to mammals. Parallels can be drawn for comparable evolution of vocal flexibility (specifically the reproduction of human speech) in birds. I describe several such parallels and conclude that MacNeilage's hypotheses may have broader application than he envisioned.