Seven and up: individual differences in male voice fundamental frequency emerge before puberty and remain stable throughout adulthood

Voice pitch (the perceptual correlate of fundamental frequency, F0) varies considerably even among individuals of the same sex and age, communicating a host of socially and evolutionarily relevant information. However, due to the almost exclusive utilization of cross-sectional designs in previous studies, it remains unknown whether these individual differences in voice pitch emerge before, during or after sexual maturation, and whether voice pitch remains stable into adulthood. Here, we measured the F0 parameters of men who were recorded once every 7 years from age 7 to 56 as they participated in the British television documentary Up Series. Linear mixed models revealed significant effects of age on all F0 parameters, wherein F0 mean, minimum, maximum and the standard deviation of F0 showed sharp pubertal decreases between age 7 and 21, yet remained remarkably stable after age 28. Critically, men's pre-pubertal F0 at age 7 strongly predicted their F0 at every subsequent adult age, explaining up to 64% of the variance in post-pubertal F0. This finding suggests that between-individual differences in voice pitch that are known to play an important role in men's reproductive success are in fact largely determined by age 7, and may therefore be linked to prenatal and/or pre-pubertal androgen exposure

Influence of ambient water coloration on habitat and conspecific choice in the female Lake Malawi cichlid, \u3ci\u3eMetriaclima zebra\u3c/i\u3e

Female cichlid fish living in African great lakes are known to have sensory systems that are adapted to ambient light environments. These sensory system adaptations are hypothesized to have influenced the evolution of the diverse male nuptial coloration. In rock-dwelling Lake Malawi mbuna cichlids, however, the extent to which ambient light environments influence female sensory systems and potentially associated male nuptial coloration remains unknown. Yet, the ubiquitous blue flank coloration and UV reflection of male mbuna cichlids suggest the potential impacts of the blue-shifted ambient light environment on these cichlid’s visual perception and male nuptial coloration in the shallow water depth in Lake Malawi. In the present study, we explored whether and how the sensory bias of females influences intersexual communication in the mbuna cichlid, Metriaclima zebra. A series of choice experiments in various light environments showed that M. zebra females 1) have a preference for the blue-shifted light environment, 2) prefer to interact with males in blue-shifted light environments, 3) do not show a preference between dominant and subordinate males in full-spectrum, long-wavelength filtered, and short-wavelength filtered light environments, and 4) show a “reversed” preference for subordinate males in the UV-filtered light environment. These results suggest that the visual perception of M. zebra females may be biased to the ambient light spectra in their natural habitat by local adaptation and that this sensory bias may influence the evolution of blue and UV reflective patterns in male nuptial coloration

Dog-directed speech: why do we use it and do dogs pay attention to it?

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' behaviour. We recorded adult participants speaking in front of pictures of puppies, adult and old dogs, and analysed the quality of their speech. We then performed playback experiments to assess dogs' reaction to dog-directed speech compared with normal speech. We found that human speakers used dog-directed speech with dogs of all ages and that the acoustic structure of dog-directed speech was mostly independent of dog age, except for sound pitch which was relatively higher when communicating with puppies. Playback demonstrated that, in the absence of other non-auditory cues, puppies were highly reactive to dog-directed speech, and that the pitch was a key factor modulating their behaviour, suggesting that this specific speech register has a functional value in young dogs. Conversely, older dogs did not react differentially to dog-directed speech compared with normal speech. The fact that speakers continue to use dog-directed with older dogs therefore suggests that this speech pattern may mainly be a spontaneous attempt to facilitate interactions with non-verbal listeners

What the hyena's laugh tells: Sex, age, dominance and individual signature in the giggling call of Crocuta crocuta

<p>Abstract</p> <p>Background</p> <p>Among mammals living in social groups, individuals form communication networks where they signal their identity and social status, facilitating social interaction. In spite of its importance for understanding of mammalian societies, the coding of individual-related information in the vocal signals of non-primate mammals has been relatively neglected. The present study focuses on the spotted hyena <it>Crocuta crocuta</it>, a social carnivore known for its complex female-dominated society. We investigate if and how the well-known hyena's laugh, also known as the giggle call, encodes information about the emitter.</p> <p>Results</p> <p>By analyzing acoustic structure in both temporal and frequency domains, we show that the hyena's laugh can encode information about age, individual identity and dominant/subordinate status, providing cues to receivers that could enable assessment of the social position of an emitting individual.</p> <p>Conclusions</p> <p>The range of messages encoded in the hyena's laugh is likely to play a role during social interactions. This call, together with other vocalizations and other sensory channels, should ensure an array of communication signals that support the complex social system of the spotted hyena. Experimental studies are now needed to decipher precisely the communication network of this species.</p

Adult human perception of distress in the cries of bonobo, chimpanzee, and human infants

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 argued that interspecific communication of emotions can fail due to species-specific signalling traits impairing information decoding and/or absence of familiarity with heterospecific communication systems. In this article, we show that human listeners pay attention to the mean pitch of vocalizations when asked to rate the distress level expressed by human baby cries, and that they use a similar pitch scale to rate the emotional level of baby non-human ape (bonobo and chimpanzee) distress calls. As a consequence, the very high-pitched bonobo infant calls were systematically rated as expressing overall high distress levels despite being recorded in contexts eliciting various stress intensity. Conversely, chimpanzee infant calls – which are characterized by a relatively lower pitch – were systematically rated as expressing relatively lower distress levels. These results indicate that, in the absence of exposure/familiarity, our spontaneous ability to range the emotional content of vocalizations in closely related ape species remains biased by basic frequency differences, suggesting that the absolute interspecific value of emotional signals should not be overestimated

Enduring voice recognition in bonobos

We would like to thank the French Ministère de l’Enseignement Supérieur et de la Recherche (PhD grant to SK), the Université de Saint-Etienne (research sabbaticals to FL and NM, visiting professorship to KZ and research funding) and the European Research Council (KZ grant PRILANG 283871).Long-term social recognition is vital for species with complex social networks, where familiar individuals can encounter one another after long periods of separation. For non-human primates who live in dense forest environments, visual access to one another is often limited, and recognition of social partners over distances largely depends on vocal communication. Vocal recognition after years of separation has never been reported in any great ape species, despite their complex societies and advanced social intelligence. Here we show that bonobos, Pan paniscus, demonstrate reliable vocal recognition of social partners, even if they have been separated for five years. We experimentally tested bonobos' responses to the calls of previous group members that had been transferred between captive groups. Despite long separations, subjects responded more intensely to familiar voices than to calls from unknown individuals - the first experimental evidence that bonobos can identify individuals utilising vocalisations even years after their last encounter. Our study also suggests that bonobos may cease to discriminate between familiar and unfamiliar individuals after a period of eight years, indicating that voice representations or interest could be limited in time in this species.Publisher PDFPeer reviewe

Effect of pitch range on dogs’ response to conspecific vs. heterospecific distress cries

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 hearing human cries, we explore whether their responses to distress cries from human infants and puppies depend upon sharing conspecific frequency range or species-specific call characteristics. We recorded adult dogs’ responses to distress cries from puppies and human babies, emitted from a loudspeaker in a basket. The frequency of the cries was presented in both their natural range and also shifted to match the other species. Crucially, regardless of species origin, calls falling into the dog call-frequency range elicited more attention. Thus, domestic dogs’ responses depended strongly on the frequency range. Females responded both faster and more strongly than males, potentially reflecting asymmetries in parental care investment. Our results suggest that, despite domestication leading to an increased overall responsiveness to human cues, dogs still respond considerably less to calls in the natural human infant range than puppy range. Dogs appear to use a fast but inaccurate decision-making process to determine their response to distress-like vocalisations

Singing in the Rain Forest: How a Tropical Bird Song Transfers Information

How information transmission processes between individuals are shaped by natural selection is a key question for the understanding of the evolution of acoustic communication systems. Environmental acoustics predict that signal structure will differ depending on general features of the habitat. Social features, like individual spacing and mating behavior, may also be important for the design of communication. Here we present the first experimental study investigating how a tropical rainforest bird, the white-browed warbler Basileuterus leucoblepharus, extracts various information from a received song: species-specific identity, individual identity and location of the sender. Species-specific information is encoded in a resistant acoustic feature and is thus a public signal helping males to reach a wide audience. Conversely, individual identity is supported by song features susceptible to propagation: this private signal is reserved for neighbors. Finally, the receivers can locate the singers by using propagation-induced song modifications. Thus, this communication system is well matched to the acoustic constraints of the rain forest and to the ecological requirements of the species. Our results emphasize that, in a constraining acoustic environment, the efficiency of a sound communication system results from a coding/decoding process particularly well tuned to the acoustic properties of this environment