We report on the emergence of functional flexibility in vocalizations of human infants. This vastly underappreciated capability becomes apparent when prelinguistic vocalizations express a full range of emotional content-positive, neutral, and negative. The data show that at least three types of infant vocalizations (squeals, vowel-like sounds, and growls) occur with this full range of expression by 3-4 mo of age. In contrast, infant cry and laughter, which are speciesspecific signals apparently homologous to vocal calls in other primates, show functional stability, with cry overwhelmingly expressing negative and laughter positive emotional states. Functional flexibility is a sine qua non in spoken language, because all words or sentences can be produced as expressions of varying emotional states and because learning conventional "meanings" requires the ability to produce sounds that are free of any predetermined function. Functional flexibility is a defining characteristic of language, and empirically it appears before syntax, word learning, and even earlier-developing features presumed to be critical to language (e.g., joint attention, syllable imitation, and canonical babbling). The appearance of functional flexibility early in the first year of human life is a critical step in the development of vocal language and may have been a critical step in the evolution of human language, preceding protosyntax and even primitive single words. Such flexible affect expression of vocalizations has not yet been reported for any nonhuman primate but if found to occur would suggest deep roots for functional flexibility of vocalization in our primate heritage.esearch on evolution and development of language has been devoted primarily to syntax, the uniquely human capacity to produce well-formed complex sentences (1-4). Additional work has targeted the emergence of simpler communicative structures and thus has shifted attention back in evolutionary time to an earlier possible split of hominins from the primate background. For example, research has considered the presumably earlier evolution of simple sentences or "protosyntax" (5). Other work influenced by recent trends in evolutionary developmental biology (evo-devo) (6, 7) has focused on infrastructure for language, invoking capabilities logically more foundational even than protosyntax and presumably moving the communicative differentiation of hominins from other primates much farther back. For example, symbolic expression in single words beginning in modern human development at about 12 mo is a precursor to even the simplest syntax (8). Moving the evolutionary focus even farther back in time, joint attention-infant pointing with gaze alternation between an object and an adult interactor, occurring before the end of the first year-is deemed a critical precursor to words (9). Similarly, canonical babbling (onset at about 7 mo) is a crucial step toward verbal vocabulary because development and imitation of canonical syllables (e.g., "baba") is required for extensive word lear...

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Infant phonation is highly variable in many respects, including the basic vibratory patterns by which the vocal tissues create acoustic signals. Previous studies have identified the regular occurrence of non-modal phonation types in normal infant phonation. The glottis is like many oscillating systems that, because of non-linear relationships among the elements, may vibrate in ways representing the deterministic patterns classified theoretically within the mathematical framework of non-linear dynamics. The infant's pre-verbal vocal explorations present such a variety of phonations that it may be possible to find effectively all the classes of vibration predicted by non-linear dynamic theory. The current report defines acoustic criteria for an important subset of such vibratory regimes, and demonstrates that analysts can be trained to reliably use these criteria for a classification that includes all instances of infant phonation in the recorded corpora. The method is thus internally comprehensive in the sense that all phonations are classified, but it is not exhaustive in the sense that all vocal qualities are thereby represented. Using the methods thus developed, this study also demonstrates that the distributions of these phonation types vary significantly across sessions of recording in the first year of life, suggesting developmental changes. The method of regime classification is thus capable of tracking changes that may be indicative of maturation of the mechanism, the learning of categories of phonatory control, and the possibly varying use of vocalizations across social contexts.

Purpose The prelinguistic infant’s babbling repertoire of syllables—the phonological categories that form the basis for early word learning—is noticed by caregivers who interact with infants around them. Prior research on babbling has not explored the caregiver’s role in recognition of early vocal categories as foundations for word learning. In the present work, the authors begin to address this gap. Method The authors explored vocalizations produced by 8 infants at 3 ages (8, 10, and 12 months) in studies illustrating identification of phonological categories through caregiver report, laboratory procedures simulating the caregiver’s natural mode of listening, and the more traditional laboratory approach (phonetic transcription). Results Caregivers reported small repertoires of syllables for their infants. Repertoires of similar size and phonetic content were discerned in the laboratory by judges who simulated the caregiver’s natural mode of listening. However, phonetic transcription with repeated listening to infant recordings yielded repertoire sizes that vastly exceeded those reported by caregivers and naturalistic listeners. Conclusions The results suggest that caregiver report and naturalistic listening by laboratory staff can provide a new way to explore key characteristics of early infant vocal categories, a way that may provide insight into later speech and language development.

Abstract:Aging of the larynx is characterized by involutional changes which alter its biomechanical and neural properties and create a biological environment that is different from younger counterparts. Illustrative anatomical examples are presented. This natural, non-disease process appears to set conditions which may infl uence the effectiveness of botulinum toxin injection and our expectations for its success. Adductor spasmodic dysphonia, a type of laryngeal dystonia, is typically treated using botulinum toxin injections of the vocal folds in order to suppress adductory muscle spasms which are disruptive to production of speech and voice. A few studies have suggested diminished response to treatment in older patients with adductor spasmodic dysphonia. This retrospective study provides a reanalysis of existing pre-to-post treatment data as function of age. Perceptual judgments of speech produced by 42 patients with ADSD were made by two panels of professional listeners with expertise in voice or fl uency of speech. Results demonstrate a markedly reduced positive response to botulinum toxin treatment in the older patients. Perceptual fi ndings are further elucidated by means of acoustic spectrography. Literature on vocal aging is reviewed to provide a specifi c set of biological mechanisms that best account for the observed interaction of botulinum toxin treatment with advancing age.