- Infrastructural theory of human language and its origins
- Empirical work on origins of communication in humans and animals (human infants and children, bonobos, dog, wolf, and squid)
- Studies of communication development in typically developing human infants
- Studies of vocal development in infants with or at risk for disorders (autism, premature birth, deafness, Down syndrome, Fragile X, low socio-economic status)
- Multicultural studies of vocal development
- Automated computational analysis of infant vocal development and vocal disorders
Infrastructural theory of human language and its origins
- Oller, D. K. The Emergence of the Speech Capacity (2000). Erlbaum. This project and its publications provide a theoretical framework for all the other projects in the laboratory, and a basis for collaboration with a wide variety of additional institutions and scholars. The key idea is that language is founded in capabilities that emerge systematically and in an ordered fashion starting in very early infancy. Primitive capabilities to vocalize and use vocalization as well as to express affect facially and through bodily movements form the basis for more advanced capabilities that are built upon them.
- Oller, D. K., Dale, R., Griebel, U. (2016). New frontiers in language evolution and development: the Editors’ Introduction. In New Frontiers in Language Evolution and Development Edited by: Wayne D. Gray. Topics in Cognitive Science (topiCS), 8(2), 353-360. Abstract: This article introduces the Special Issue and its focus on research in language evolution with emphasis on theory as well as computational and robotic modeling. A key theme is based on the growth of evolutionary developmental biology or evo-devo. The Special Issue consists of 13 articles organized in two sections: A) Theoretical foundations and B) Modeling and simulation studies. All the papers are interdisciplinary in nature, encompassing work in biological and linguistic foundations for the study of language evolution as well as a variety of computational and robotic modeling efforts shedding light on how language may be developed and may have evolved.
- Oller, D. K., Griebel, U., & Warlaumont, A. S. (2016). Vocal development as a guide to modeling the evolution of language. In New Frontiers in Language Evolution and Development Edited by: Wayne D. Gray. Topics in Cognitive Science (topiCS), 8(2), 382-392. Abstract: Modeling of evolution and development of language has principally utilized mature units of spoken language, phonemes and words, as both targets and inputs. This approach cannot address the earliest phases of development because young infants are unable to produce such language features. We argue that units of early vocal development—protophones and their primitive illocutionary/perlocutionary forces—should be targeted in evolutionary modeling because they suggest likely units of hominin vocalization/communication shortly after the split from the chimpanzee/bonobo lineage, and because early development of spontaneous vocal capability is a logically necessary step toward vocal language, a root capability without which other crucial steps toward vocal language capability are impossible. Modeling of language evolution/development must account for dynamic change in early communicative units of form/function across time. We argue for interactive contributions of sender/infants and receiver/caregivers in a feedback loop involving both development and evolution and propose to begin computational modeling at the hominin break from the primate communicative background.
Empirical work on origins of communication in humans and animals (human infants and children, bonobos, dog, wolf, and squid)
- Griebel, U. & Oller, D. K. (2008). Evolutionary forces favoring contextual flexibility. In Oller, D.K. and Griebel, U. (editors) Evolution of Communicative Flexibility: Complexity, Creativity, and Adaptability in Human and Animal Communication, MIT Press pp. 9-40. This chapter defines “signal flexibility” and “functional flexibility” as two kinds of contextual flexibility in communication. It evaluates the environmental/social conditions and communication types that seem to favor selection for variability or complexity in communication systems and which may result in signal and functional flexibility. The chapter also presents clear cases of actions such as camouflage and deception, and proposes that some degree of signal flexibility is a prerequisite for functional flexibility. It analyzes the occurrence of the various mapping options for signals and functions in nonhumans from invertebrates to primates, and suggests that human communicative flexibility first emerged under pressures of social cohesion.
- Griebel, U., & Oller, D. K. (2014). Origins of language in a comparative perspective. In P. J. Lafreniere & G. Weisfeld (Eds.), Evolutionary Science of Human Behavior: An Interdisciplinary Approach. Linus Learning, Rokokoma, NY. 257-280. Since our cognitive abilities have evolved from those of our ancestors, we suggest a comparative approach to enlightening us about language origins, examining animal language learning studies to determine what animals actually can come to understand about human language. This approach may lead to better understanding of the cognitive underpinnings of language. It will definitely help to pinpoint features that seem to be uniquely involved in human language, ones that may be present to lesser extents in animal communication, as well as ones that are shared across many species.
- Oller, D. K. & Griebel, U. (2014). On Quantitative Comparative Research in Communication and Language Evolution. Biological Theory, 9, 2, 296-308. doi: 10.1007/s13752-014-0186-7. NIHMSID #613148. PMCID: PMC4179202. Abstract: Quantitative comparison of human language and natural animal communication requires improved conceptualizations. We argue that an infrastructural approach to development and evolution incorporating an extended interpretation of the distinctions among illocution, perlocution, and meaning (Austin 1962; Oller and Griebel 2008) can help place the issues relevant to quantitative comparison in perspective. The approach can illuminate the controversy revolving around the notion of functional referentiality as applied to alarm calls, for example in the vervet monkey. We argue that referentiality offers a poor point of quantitative comparison across language and animal communication in the wild. Evidence shows that even newborn human cry could be deemed to show functional referentiality according to the criteria typically invoked by advocates of referentiality in animal communication. Exploring the essence of the idea of illocution, we illustrate an important realm of commonality among animal communication systems and human language, a commonality that opens the door to more productive, quantifiable comparisons. Finally, we delineate two examples of infrastructural communicative capabilities that should be particularly amenable to direct quantitative comparison across humans and our closest relatives.
- Griebel, U., Pepperberg, I., Oller, D. K. (2016). Developmental Plasticity and Language: A Comparative Perspective. In New Frontiers in Language Evolution and Development Edited by: Wayne D. Gray. Topics in Cognitive Science (topiCS). 8(2), 435-445. Abstract: The growing field of evo-devo is increasingly demonstrating the complexity of steps involved in genetic, intracellular regulatory, and extracellular environmental control of the development of phenotypes. A key result of such work is an account for the remarkable plasticity of organismal form in many species based on relatively minor changes in regulation of highly conserved genes and genetic processes. Accounting for behavioral plasticity is of similar potential interest but has received far less attention. Of particular interest is plasticity in communication systems, where human language represents an ultimate target for research. The present paper considers plasticity of language capabilities in a comparative framework, focusing attention on examples of a remarkable fact: Whereas there exist design features of mature human language that have never been observed to occur in non-humans in the wild, many of these features can be developed to notable extents when non-humans are enculturated through human training (especially with intensive social interaction). These examples of enculturated developmental plasticity across extremely diverse taxa suggest, consistent with the evo-devo theme of highly conserved processes in evolution, that human language is founded in part on cognitive capabilities that are indeed ancient and that even modern humans show self-organized emergence of many language capabilities in the context of rich enculturation, built on the special social/ecological history of the hominin line. Human culture can thus be seen as a regulatory system encouraging language development in the context of a cognitive background with many highly conserved features.
- Tchernichovski, O. & Oller, D. K. (2016) Vocal Development: How marmoset infants express their feelings. Current Biology. 26(10), R422-R424. Abstract: A new study shows that vocal sequences produced by newborn marmoset monkeys are driven by slow fluctuations in physiological state; the results shed light on the evolution of vocal communication between newborns and parents.
- Griebel U., Oller D.K. (2012) Vocabulary learning in a Yorkshire terrier: Slow mapping of spoken words. PLoS ONE. 7(2): e30182. doi:10.1371/journal.pone.0030182. Abstract: Rapid vocabulary learning in children has been attributed to "fast mapping", with new words often claimed to be learned through a single presentation. As reported in 2004 in Science a border collie (Rico) not only learned to identify more than 200 words, but fast mapped the new words, remembering meanings after just one presentation. Our research tests the fast mapping interpretation of the Science paper based on Rico's results, while extending the demonstration of large vocabulary recognition to a lap dog. We tested a Yorkshire terrier (Bailey) with the same procedures as Rico, illustrating that Bailey accurately retrieved randomly selected toys from a set of 117 on voice command of the owner. Second we tested her retrieval based on two additional voices, one male, one female, with different accents that had never been involved in her training, again showing she was capable of recognition by voice command. Third, we did both exclusion-based training of new items (toys she had never seen before with names she had never heard before) embedded in a set of known items, with subsequent retention tests designed as in the Rico experiment. After Bailey succeeded on exclusion and retention tests, a crucial evaluation of true mapping tested items previously successfully retrieved in exclusion and retention, but now pitted against each other in a two-choice task. Bailey failed on the true mapping task repeatedly, illustrating that the claim of fast mapping in Rico had not been proven, because no true mapping task had ever been conducted with him. It appears that the task called retention in the Rico study only demonstrated success in retrieval by a process of extended exclusion.
Studies of communication development in typically developing human infants
- Oller, D. K., Buder, E. H., Ramsdell, H. L., Warlaumont, A. S., Chorna, L., & Bakeman, R. (2013). Functional flexibility of infant vocalization and the emergence of language. Proceedings of the National Academy of Sciences. 110 (16) 6318-6323. doi:10.1073/pnas.1300337110/-/DCSupplemental. PMCID: PMC3631625. Abstract: 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 months of age. In contrast, infant cry and laughter, which are species-specific 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 non-human primate but if found to occur would suggest deep roots for functional flexibility of vocalization in our primate heritage.
- Nathani Iyer, S., Denson, H., Lazar, N. & Oller, D. K. (2016) Volubility of the human infant: Effects of parental interaction (or lack of it). Clinical Linguistic & Phonetics. DOI:10.3109/02699206.2016.1147082, 80747, PMC4902155. Abstract: Although parental volubility, or amount of talk, has received considerable recent attention, infant volubility has received comparatively little attention despite its potential significance for communicative risk status and later linguistic and cognitive outcomes. Volubility of 16 typically developing infants from 2 to 11 months of age was longitudinally investigated in the present study across three social circumstances: parent talking to infant, parent not talking to infant and parent talking to interviewer while the infant was in the room. Results indicated that volubility was least in the Interview circumstance. There were no significant differences in volubility between the parent Talk and No Talk circumstances. Volubility was found to reduce with age. These results suggest that infants vocalize in a variety of circumstances, even when no one talks to or interacts with them. The presence of a stranger or perhaps overhearing adults speaking to each other, however, may significantly reduce infant volubility.
- Jhang. Y., & Oller, D. K (2017). Emergence of Functional Flexibility in Early Infant Vocalization of the First Three Months: Analyses of laboratory recordings. Frontiers in Psychology. 8, DOI:10.3389/fpsyg.2017.00300. Abstract: Functional flexibility, as manifest in the use of any word or sentence to express different affective valences on different occasions, is required in linguistic communication and can be said to be an infrastructural property of language. Early infant vocalizations (protophones), believed to be precursors to speech, occur in the first month and are functionally different from non-speech-like signals (e.g., cries and laughs). Oller et al. (2013) showed that infants by 3 months used three different protophone types with a full range of affect as manifest in facial expression, from positive to neutral to negative. These differences in affect were also shown to correspond to different illocutionary functions, unlike fixed signals, or vegetative sounds, which showed functional rigidity. The present study investigated whether infants show functional flexibility in protophones even earlier than the ages studied by Oller et al. (2013). Data were obtained from 6 infants across the first 3 months. Results showed that as early as the first month, infant protophones were already accompanied by variable facial affect valences and continued to be affectively flexible at the later ages. The present study thus documents the very early emergence of an infrastructural property of human communication.
- Yoo, H., Bidelman, G., Buder, E. H., van Mersbergen, M., Oller, D. K. (2017). Differentiating infant cry from non-cry vocalizations based on perception of negativity and acoustic features. The Journal of the Acoustical Society of America. 141. 3748-3749. Abstract: This study seeks to determine how human listeners discriminate cry vs. non-cry sounds by investigating acoustic factors that may contribute to the perception of negativity in infant vocalizations (e.g., cry, whine, and vowel-like sounds). The assumption is that identification of cry is self-evident; therefore, there has been no attempt to systematically differentiate cry from non-cry vocalizations. Twelve exemplars each of cry, whine, and vowel-like sound segments (36 total) were selected from archival audio recordings of infant vocalizations. Categories were selected from expert-judged audio signals of vocal development. Adult listeners identified each utterance as either cry, whine, or vowel-like sound as quickly and accurately as possible. They also judged the extent of negativity of each utterance. Acoustic features of each utterance were analyzed in association with the categories and degrees of negativity. Results suggest a continuum of negativity from cries (most negative) to vowel-like sounds (least negative), and that acoustic variables are gradated across the negativity continuum. However, preliminary results suggest that peak F0, peak RMS, and spectral slope best differentiate the categories.
- Franklin, B., Warlaumont, A. S., Messinger, D. S., Bene, E., Nathani Iyer, S., Lee, C-C., Lambert, B., Oller, D. K. (2014). Effects of Parental Interaction on Infant Vocalization Rate, Variability and Vocal Type. Language Learning and Development. 10(3):279–296. Abstract: Examination of infant vocalization patterns across interactive and noninteractive contexts may facilitate better understanding of early communication development. In the current study, with 24 infant-parent dyads, infant volubility increased significantly when parent interaction ceased (presenting a “still face,” or SF) after a period of normal interaction (“face-to-face,” or FF). Infant volubility continued at the higher rate than in FF when the parent re-engaged (“reunion,” or RE). Additionally, during SF, the variability in volubility across infants decreased, suggesting the infants adopted relatively similar rates of vocalization to re-engage the parent. The pattern of increasing volubility in SF was seen across all of the most common speech-like vocal types of the first half-year of life (e.g., full vowels, quasivowels, squeals, growls). Parent and infant volubility levels were not significantly correlated. The findings suggest that by six months of age infants have learned that their vocalizations have social value and that changes in volubility can affect parental engagement.
Studies of vocal development in infants with or at risk for disorders (autism, premature birth, deafness, Down syndrome, Fragile X, low socio-economic status)
- Oller, D. K., & Eilers, R. E. (1988). The role of audition in infant babbling. Child Development, 59, 441 449. Abstract: The traditional belief that audition plays only a minor role in infant vocal development depends upon evidence that deaf infants produce the same kinds of babbling sounds as hearing infants. Evidence in support of this position has been very limited. A more extensive comparison of vocal development in deaf and hearing infants indicates that the traditional belief is in error. Well-formed syllable production is established in the first 10 months of life by hearing infants but not by deaf infants, indicating that audition plays an important role in vocal development. The difference between babbling in the deaf and hearing is apparent if infant vocal sounds are observed from a metaphonological perspective, a view that takes account of the articulatory/acoustic patterns of speech sounds in all mature spoken languages.
- Eilers, R. E., & Oller, D. K. (1994). Infant vocalizations and the early diagnosis of severe hearing impairment. Journal of Pediatrics, 124, 199-203. Abstract: To determine whether late onset of canonical babbling could be used as a criterion to determine risk of hearing impairment, we obtained vocalization samples longitudinally from 94 infants with normal hearing and 37 infants with severe to profound hearing impairment. Parents were instructed to report the onset of canonical babbling (the production of well-formed syllables such as "da," "na," "bee," "yaya"). Verification that the infants were producing canonical syllables was collected in laboratory audio recordings. Infants with normal hearing produced canonical vocalizations before 11 months of age (range, 3 to 10 months; mode, 7 months); infants who were deaf failed to produce canonical syllables until 11 months of age or older, often well into the third year of life (range, 11 to 49 months; mode, 24 months). The correlation between age at onset of the canonical stage and age at auditory amplification was 0.68, indicating that early identification and fitting of hearing aids is of significant benefit to infants learning language. The fact that there is no overlap in the distribution of the onset of canonical babbling between infants with normal hearing and infants with hearing impairment means that the failure of otherwise healthy infants to produce canonical syllables before 11 months of age should be considered a serious risk factor for hearing impairment and, when observed, should result in immediate referral for audiologic evaluation.
- Belardi, K., Watson, L. R., Faldowski, R. A., Hazlett, H., Crais, E. R., Baranek, G. T., McComish, C., Patten, E., Oller, D. K. (2017). A retrospective video analysis of canonical babbling and volubility in infants with Fragile-X syndrome at 9-12 months of age. Journal of Autism and Developmental Disorders, 47(4), 1193-1206. doi: 10.1007/s10803-017-3033-4. Abstract: An infant’s vocal capacity develops significantly during the first year of life. Research suggests early measures of pre-speech development, such as canonical babbling and volubility, can differentiate typical versus disordered development. This study offers a new contribution by comparing early vocal development in 10 infants with Fragile X syndrome and 14 with typical development. Results suggest infants with Fragile X syndrome produce fewer syllables and have significantly lower canonical babbling ratios compared to infants who are typically developing. Furthermore, the particular measures of babbling were strong predictors of group membership, adding evidence regarding the possible utility of these markers in early identification.
- Patten, E., Belardi, K., Baranek, G., Oller, D. K. (2014). Vocal patterns in infants with Autism Spectrum Disorder: Canonical babbling status and vocalization frequency. Journal of Autism and Developmental Disorders, 44(10), 2413–2428. doi:10.1007/s10803-014-2047-4. Abstract: Canonical babbling is a critical milestone for speech development and is usually well in place by 10 months. The possibility that infants with autism spectrum disorder (ASD) show late onset of canonical babbling has so far eluded evaluation. Rate of vocalization or "volubility" has also been suggested as possibly aberrant in infants with ASD. We conducted a retrospective video study examining vocalizations of 37 infants at 9-12 and 15-18 months. Twenty-three of the 37 infants were later diagnosed with ASD and indeed produced low rates of canonical babbling and low volubility by comparison with the 14 typically developing infants. The study thus supports suggestions that very early vocal patterns may prove to be a useful component of early screening and diagnosis of ASD.
Multicultural studies of vocal development
- Lee, C-C., Jhang, Y., Chen, L., Relyea, G., Oller, D. K. (2016). Subtlety of ambient-language effects in babbling: A study of English- and Chinese-speaking infants at 8, 10, and 12 months. Language Learning and Development. DOI: 10.1080/15475441.2016.1180983. Abstract: Prior research on ambient-language effects in babbling has often suggested infants produce language-specific phonological features within the first year. These results have been questioned in research failing to find such effects and challenging the positive findings on methodological grounds. We studied English- and Chinese-learning infants at 8, 10, and 12 months and found listeners could not detect ambient-language effects in the vast majority of infant utterances, but only in items deemed to be words or to contain canonical syllables that may have made them sound like words with language-specific shapes. Thus, the present research suggests the earliest ambient-language effects may be found in emerging lexical items or in utterances influenced by language-specific features of lexical items. Even the ambient-language effects for infant canonical syllables and words were very small compared with ambient-language effects for meaningless but phonotactically well-formed syllable sequences spoken by adult native speakers of English and Chinese.
- Farran, L. K., Lee, C-C., Yoo, H., Oller, D. K. (2016). Cross-cultural register differences in infant-directed speech: An initial study. PLoS ONE. 11(3). e0151518. doi:10.1371/journal.pone.0151518. Abstract: Infant-directed speech (IDS) provides an environment that appears to play a significant role in the origins of language in the human infant. Differences have been reported in the use of IDS across cultures, suggesting different styles of infant language-learning. Importantly, both cross-cultural and intra-cultural research suggest there may be a positive relationship between the use of IDS and rates of language development, underscoring the need to investigate cultural differences more deeply. The majority of studies, however, have conceptualized IDS monolithically, granting little attention to a potentially key distinction in how IDS manifests across cultures during the first two years. This study examines and quantifies for the first time differences within IDS in the use of baby register (IDS/BR), an acoustically identifiable type of IDS that includes features such as high pitch, long duration, and smooth intonation (the register that is usually assumed to occur in IDS), and adult register (IDS/AR), the type of IDS that does not include such features and thus sounds as if it could have been addressed to an adult. We studied IDS across 19 American and 19 Lebanese mother-infant dyads, with particular focus on the differential use of registers within IDS as mothers interacted with their infants ages 0–24 months. Our results showed considerable usage of IDS/AR (>30% of utterances) and a tendency for Lebanese mothers to use more IDS than American mothers. Implications for future research on IDS and its role in elucidating how language evolves across cultures are explored.
Automated computational analysis of infant vocal development and vocal disorders
- Oller, D. K., Niyogi, P., S. Gray, J. A. Richards, J. Gilkerson, D. Xu, U. Yapanel, S. F. Warren (2010). Automated Vocal Analysis of Naturalistic Recordings from Children with Autism, Language Delay and Typical Development. Proceedings of the National Academy of Sciences, 107, 30, 13354-13359. PMCID: PMC2922144. Abstract: For generations the study of vocal development and its role in language has been conducted laboriously, with human transcribers and analysts coding and taking measurements from small recorded samples. Our research illustrates a method to obtain measures of early speech development through automated analysis of massive quantities of day-long audio recordings collected naturalistically in children's homes. A primary goal is to provide insights into the development of infant control over infrastructural characteristics of speech through large-scale statistical analysis of strategically selected acoustic parameters. In pursuit of this goal we have discovered that the first automated approach we implemented is not only able to track children's development on acoustic parameters known to play key roles in speech, but also is able to differentiate vocalizations from typically developing children and children with autism or language delay. The method is totally automated, with no human intervention, allowing efficient sampling and analysis at unprecedented scales. The work shows the potential to fundamentally enhance research in vocal development and to add a fully objective measure to the battery used to detect speech-related disorders in early childhood. Thus, automated analysis should soon be able to contribute to screening and diagnosis procedures for early disorders, and more generally, the findings suggest fundamental methods for the study of language in natural environments.
- Warren, S. F., Gilkerson, J., Richards, J., Oller, D. K., Xu, D., Yapanel, U. (2010). What automated vocal analysis reveals about the language learning environment of young children with autism. Journal of Autism and Developmental Disorders, 40, 555-569. Abstract: The study compared the vocal production and language learning environments of 26 young children with autism spectrum disorder (ASD) to 78 typically developing children using measures derived from automated vocal analysis. A digital language processor and audio-processing algorithms measured the amount of adult words to children and the amount of vocalizations they produced during 12-h recording periods in their natural environments. The results indicated significant differences between typically developing children and children with ASD in the characteristics of conversations, the number of conversational turns, and in child vocalizations that correlated with parent measures of various child characteristics. Automated measurement of the language learning environment of young children with ASD reveals important differences from the environments experienced by typically developing children.
- Woynaroski, T. G., Oller, D. K., Kaysili, B. K., Yoder, P. (2016). The stability and validity of automated vocal analysis in preverbal preschoolers with autism spectrum disorder: Automated Vocal Analysis in ASD. Autism Research. DOI: 10.1002/aur.1667 DOI: 10.1002/aur.1667. Abstract: Theory and research suggest that vocal development predicts "useful speech" in preschoolers with autism spectrum disorder (ASD), but conventional methods for measurement of vocal development are costly and time consuming. This longitudinal correlational study examines the reliability and validity of several automated indices of vocalization development relative to an index derived from human coded, conventional communication samples in a sample of preverbal preschoolers with ASD. Automated indices of vocal development were derived using software that is presently "in development" and/or only available for research purposes and using commercially available Language ENvironment Analysis (LENA) software. Indices of vocal development that could be derived using the software available for research purposes: (a) were highly stable with a single day-long audio recording, (b) predicted future spoken vocabulary to a degree that was nonsignificantly different from the index derived from conventional communication samples, and (c) continued to predict future spoken vocabulary even after controlling for concurrent vocabulary in our sample. The score derived from standard LENA software was similarly stable, but was not significantly correlated with future spoken vocabulary. Findings suggest that automated vocal analysis is a valid and reliable alternative to time intensive and expensive conventional communication samples for measurement of vocal development of preverbal preschoolers with ASD in research and clinical practice.
- Warlaumont, A. S., Richards, J. A., Gilkerson, J. & Oller, D. K. (2014). A Social Feedback Loop for Speech Development and Its Reduction in Autism. Psychological Science, 25: 1314-1324. DOI: 10.1177/0956797614531023 NIHMS577758. Abstract: We analyzed the microstructure of child-adult interaction during naturalistic, daylong, automatically labeled audio recordings (13,836 hr total) of children (8- to 48-month-olds) with and without autism. We found that an adult was more likely to respond when the child's vocalization was speech related rather than not speech related. In turn, a child's vocalization was more likely to be speech related if the child's previous speech-related vocalization had received an immediate adult response rather than no response. Taken together, these results are consistent with the idea that there is a social feedback loop between child and caregiver that promotes speech development. Although this feedback loop applies in both typical development and autism, children with autism produced proportionally fewer speech-related vocalizations, and the responses they received were less contingent on whether their vocalizations were speech related. We argue that such differences will diminish the strength of the social feedback loop and have cascading effects on speech development over time. Differences related to socioeconomic status are also reported.
- Abney, D. H., Warlaumont, A. S., Oller, D. K., Wallot, S., & Kello, C. T. (2016). Multiple Coordination Patterns in Infant and Adult Vocalizations. Infancy, 9, 1. doi:10.1111/infa.12165. Abstract: The study of vocal coordination between infants and adults has led to important insights into the development of social, cognitive, emotional, and linguistic abilities. We used an automatic system to identify vocalizations produced by infants and adults over the course of the day for fifteen infants studied longitudinally during the first 2 years of life. We measured three different types of vocal coordination: coincidence-based, rate-based, and cluster-based. Coincidence-based coordination and rate-based coordination are established measures in the developmental literature. Cluster-based coordination is new and measures the strength of matching in the degree to which vocalization events occur in hierarchically nested clusters. We investigated whether various coordination patterns differ as a function of vocalization type, whether different coordination patterns provide unique information about the dynamics of vocal interaction, and how the various coordination patterns each relate to infant age. All vocal coordination patterns displayed greater coordination for infant speech-related vocalizations, adults adapted the hierarchical clustering of their vocalizations to match that of infants, and each of the three coordination patterns had unique associations with infant age. Altogether, our results indicate that vocal coordination between infants and adults is multifaceted, suggesting a complex relationship between vocal coordination and the development of vocal communication.
- Gilkerson, J., Richards, J.A., Warren, S. F., Greenwood, C. R., Oller, D. K., Montgomery, J. K., Hansen, J. H. L., Xu, D. & Paul, T. D. (2017). Mapping the early language environment using all-day recordings and automated analysis. American Journal of Speech Language Pathology. doi:10.1044/2016. Abstract: Purpose: This research provided a first-generation standardization of automated language environment estimates, validated these estimates against standard language assessments, and extended on previous research reporting language behavior differences across socioeconomic groups. Method: Typically developing children between 2 to 48 months of age completed monthly, daylong recordings in their natural language environments over a span of approximately 6-38 months. The resulting data set contained 3,213 12-hr recordings automatically analyzed by using the Language Environment Analysis (LENA) System to generate estimates of (a) the number of adult words in the child's environment, (b) the amount of caregiver-child interaction, and (c) the frequency of child vocal output. Results: Child vocalization frequency and turn-taking increased with age, whereas adult word counts were age independent after early infancy. Child vocalization and conversational turn estimates predicted 7%-16% of the variance observed in child language assessment scores. Lower socioeconomic status (SES) children produced fewer vocalizations, engaged in fewer adult-child interactions, and were exposed to fewer daily adult words compared with their higher socioeconomic status peers, but within-group variability was high. Conclusions: The results offer new insight into the landscape of the early language environment, with clinical implications for identification of children at-risk for impoverished language environments.
- Warlaumont, A. S., Oller, D. K., Buder, E. H., & Westermann, G. (2013). Prespeech motor learning in a neural network using reinforcement. Neural Networks, 38, 64–75. PMCID: PMC3541464. doi:10.1016.j.neunet.2012.11.012. Abstract: Vocal motor development in infancy provides a crucial foundation for language development. Some significant early accomplishments include learning to control the process of phonation (the production of sound at the larynx) and learning to produce the sounds of one's language. Previous work has shown that social reinforcement shapes the kinds of vocalizations infants produce. We present a neural network model that provides an account of how vocal learning may be guided by reinforcement. The model consists of a self-organizing map that outputs to muscles of a realistic vocalization synthesizer. Vocalizations are spontaneously produced by the network. If a vocalization meets certain acoustic criteria, it is reinforced, and the weights are updated to make similar muscle activations increasingly likely to recur. We ran simulations of the model under various reinforcement criteria and tested the types of vocalizations it produced after learning in the different conditions. When reinforcement was contingent on the production of phonated (i.e. voiced) sounds, the network's post-learning productions were almost always phonated, whereas when reinforcement was not contingent on phonation, the network's post-learning productions were almost always not phonated. When reinforcement was contingent on both phonation and proximity to English vowels as opposed to Korean vowels, the model's post-learning productions were more likely to resemble the English vowels and vice versa.