Infant-directed Speech Research Articles

How do Audible Message Notifications Influence the Quantity and Quality of Child-Directed Speech from Parents?

The impact of direct mobile phone usage on child-directed speech (CDS) has been frequently explored. However, little is known about the effects of passive mobile phone interaction regarding this aspect. Using a repeated measures design with counterbalancing and a yoked control design, the present study examines the influence of audible message notifications on the quantity and quality of CDS delivered by parents. Results indicate that receiving message notifications reduces both the amount and quality of CDS and that a familiar message notification has a greater effect on diminishing parent-child interaction than an unfamiliar message notification. The findings thus have implications for parents, highlighting the importance of reducing passive mobile phone usage to construct a better language-learning environment for toddlers.

Revisiting frequencies of phonological sound classes in speech input: Change over time in child-directed speech.

The purpose of the current study was to revisit a controversial topic: whether frequencies of phonological consonant and vowel classes differ in speech directed to children and to adults. In addition, the current study investigated whether the frequency of phonological consonant and vowel classes changes with children's increasing chronological and/or developmental age. This study analyzed speech input from 44 adults to four different age groups of listeners (i.e., three groups of children at 6, 18, and 36 months of age and one group of adult listeners) in terms of frequency of occurrence of consonant and vowel classes. Results revealed that consonant stop, nasal, fricative and glide manner classes as well as all four consonant place classes were significantly different in speech directed to the four different age groups. A perspective is discussed to better understand the nature of frequency input of phonological sound classes.

The acquisition of the passive voice in Northern East Cree

This article analyzes the acquisition of the passive voice in Northern East (NE) Cree and pays particular attention to the interaction of frequency effects and language-specific cues in the way children form and employ expectations, the process of anticipating oncoming structure in the ambient language. The passive has long been of interest in first-language acquisition, and expectations may play a role in the reported challenges acquiring the passive in languages such as English. We present two studies analyzing approximately 24 hours of naturalistic video recordings involving one adult and two children: Daisy (age 3;08–5;11) and Billy (4;06–5;10). Study 1 examines the passive voice in child-directed speech (CDS). CDS employs passive verbs frequently, at rates much higher than what has been reported for other languages. Passives also typically occur without overt arguments and most often are derived from verbs with two animate participants. Study 2 traces the acquisition of the passive by Daisy and Billy. Daisy demonstrates productivity with all three passive suffixes by age 3;11. Billy’s recordings begin at a later age, and he shows productivity with suffixes -naaniu at 4;06, -ikiwi at 4;10, and -ikiniw at 5;05. Both children produce passives at rates much higher than what has been reported in child speech for other languages. They also most frequently produce passives without overt arguments, and they show no difficulties passivizing verbs with two animate arguments. These results expand the typological purview of passives research and shed additional light on the role of expectations in acquiring the passive voice. The combination of high frequency and particular structural characteristics for the passive voice in Cree CDS allows children to build expectations differing greatly from those of children acquiring languages such as English. In turn, children acquiring NE Cree do not show the same difficulties in acquiring the passive voice.

Maternal beliefs about infant-directed speech misalign with interactions with their infants

IntroductionInfant-directed speech (IDS) refers to how people in many societies talk with young children. Compared to speech directed to an adult (ADS), IDS includes a slower rate, fewer words per utterance, higher-than-average pitch, and elongated vowels. Although many benefits are associated with using IDS, there is little information on what parents think about IDS. The current study asked: (1) How do mothers conceptualize IDS; (2) Is there an alignment between mothers' IDS beliefs and their speech register when teaching a new word to their child; and (3) How do mothers' IDS beliefs associate with children's expressive language and performance on a word learning task?MethodsFifty-three mothers and their 15- to 21-month-old monolingual English-reared infants (Mage = 17.92, SD = 1.99, 23 males) participated. Mothers were asked to teach their child a novel word and to complete the Parent Language Belief Questionnaire (PLBQ). Mothers' IDS was recorded as they taught their child a novel word and was compared to their ADS from interacting with the experimenter.ResultsFindings revealed that mothers had mixed beliefs about their use of IDS. Yet, most mothers used IDS as they taught their child a novel word. Lastly, mothers' IDS beliefs did not predict children's language skills or word learning at test.DiscussionThe current study is the first to explore whether mothers' beliefs about their use of infant-directed speech align with their actual use of IDS. As the positive benefits between IDS and children's language development have been documented, identifying the barriers surrounding why parents may not use IDS with their children is essential.

Description of Locomotion Events: Language-Specific Patterns in Child-Directed Speech

Description of Locomotion Events: Language-Specific Patterns in Child-Directed Speech

The lexical representation of coda /t/ by 14-month-olds

We evaluated 14-month-olds’ lexical representation of coda /t/. Pronunciation variation of /t/, one of the most frequent segments in English, is well documented. Crucially, in American English infant-directed speech, /t/s are most often produced as glottal stops. This is particularly the case in word-final position, where words like cat and night are produced as [kæʔ] and [naiʔ] around 42% of the time, but produced with word-final canonical stop consonants (e.g., [kæt] or [nait]) only 25% of the time. In Experiment 1, we found that infants preferred to listen to familiar monosyllabic words ending in glottal stops (like [kæʔ]) when compared to nonce words ([kɪp]). This suggests that infants encode the most frequently occurring variant in their lexical entries. We are now testing whether the preference for familiar words produced with a glottal stop in Experiment 1 is the result of coda underspecification or encoding of glottal stop. If codas are underspecified in infant’s lexical representations, we expect no preference between lists of familiar words with glottal stops ([kæʔ]), compared to minimal pairs with coda mispronunciations ([kæk]). We will discuss implications of these findings for infants’ developing lexical representations and knowledge of allophony, focusing on the contribution of input frequency.

Parent–toddler play talk: Toddler speech is differentially associated with paternal and maternal speech in interaction

Children’s speech is influenced by the speech they hear, in particular by the parental speech addressed directly to them. The aim of this study was to analyse toddlers’ speech with their parents and to investigate the influence of specific characteristics of child-directed speech on child speech in real time during mother–child and father–child dyadic interactions. Eighty-four children ( M = 24.11 months, SD = 1.37, 42 girls) and their parents were video-recorded in dyadic freeplay. Parent and child speech was compared on measures of quantity (number of words), quality (vocabulary diversity, proportion, and composition of nouns/verbs) and productivity or complexity. Overall findings reveal very similar speech produced by mothers and fathers with their toddlers and by toddlers with each parent, with the exception of vocabulary diversity patterns. Furthermore, the child-directed speech of mothers and fathers was differently associated with child speech in interaction. Findings suggest that children may be exposed to different lexical sets by mother and father and there may be added value for the child of engaging in separate dyadic interactions with mother and father. Implications for research include sampling child speech across contexts and conversational partners.

Neural responses to natural and enhanced speech edges in children with and without dyslexia.

Sensory-neural studies indicate that children with developmental dyslexia show impairments in processing acoustic speech envelope information. Prior studies suggest that this arises in part from reduced sensory sensitivity to amplitude rise times (ARTs or speech "edges") in the envelope, accompanied by less accurate neural encoding of low-frequency envelope information. Accordingly, enhancing these characteristics of the speech envelope may enhance neural speech processing in children with dyslexia. Here we applied an envelope modulation enhancement (EME) algorithm to a 10-min story read in child-directed speech (CDS), enhancing ARTs and also enhancing low-frequency envelope information. We compared neural speech processing (as measured using MEG) for the EME story with the same story read in natural CDS for 9-year-old children with and without dyslexia. The EME story affected neural processing in the power domain for children with dyslexia, particularly in the delta band (0.5-4 Hz) in the superior temporal gyrus. This may suggest that prolonged experience with EME speech could ameliorate some of the impairments shown in natural speech processing by children with dyslexia.

Phonological Variation in Child-Directed Speech is Modulated by Lexical Frequency.

We investigate whether child-directed speech (CDS) contains a higher proportion of canonical pronunciations compared to adult-directed speech (ADS), focusing on Korean noun stem-final obstruent variation. In a word-teaching task, we observed that mothers use a higher rate of canonical pronunciation when addressing infants than when addressing adults. In a follow-up experiment, adults exhibited a higher rate of canonical pronunciation for high- than low-frequency words. Additional analyses conducted with only the high-frequency monosyllabic words from the two experiments found no evidence for simplified phonology in CDS when lexical frequency was controlled for. Our findings suggest that the higher rate of canonical forms in CDS, with respect to Korean morphophonological rules, is mediated by the frequency of word usage. Thus, the didactic function of CDS phonology appears to be a byproduct of mothers using familiar words with children. These results highlight the importance of considering word usage in investigating the nature of CDS.

Mothers' and fathers' infant-directed speech have similar acoustic properties, but these are not associated with direct or indirect measures of word comprehension in 8-month-old infants.

Previous research on infant-directed speech (IDS) and its role in infants' language development has largely focused on mothers, with fathers being investigated scarcely. Here we examine the acoustics of IDS as compared to adult-directed speech (ADS) in Norwegian mothers and fathers to 8-month-old infants, and whether these relate to direct (eye-tracking) and indirect (parental report) measures of infants' word comprehension. Forty-five parent-infant dyads participated in the study. Parents (24 mothers, 21 fathers) were recorded reading a picture book to their infant (IDS), and to an experimenter (ADS), ensuring identical linguistic context across speakers and registers. Results showed that both mothers' and fathers' IDS had exaggerated prosody, expanded vowel spaces, as well as more variable and less distinct vowels. We found no evidence that acoustic features of parents' speech were associated with infants' word comprehension. Potential reasons for the lack of such a relationship are discussed.

Real-time monitoring of infant theta power during naturalistic social experiences

Infant-directed speech and direct gaze are important social cues that shape infant’s attention to their parents. Traditional methods for probing their effect on infant attention involve a small number of pre-selected screen-based stimuli, which do not capture the complexity of real-world interactions. Here, we used neuroadaptive Bayesian Optimization (NBO) to search a large ‘space’ of different naturalistic social experiences that systematically varied in their visual (gaze direct to averted) and auditory properties (infant directed speech to nonvocal sounds). We measured oscillatory brain responses (relative theta power) during episodes of naturalistic social experiences in 57 typically developing 6- to 12-month-old infants. Relative theta power was used as input to the NBO algorithm to identify the naturalistic social context that maximally elicited attention in each individual infant. Results showed that individual infants were heterogeneous in the stimulus that elicited maximal theta with no overall stronger attention for direct gaze or infant-directed speech; however, individual differences in attention towards averted gaze were related to interpersonal skills and greater likelihood of preferring speech and direct gaze was observed in infants whose parents showed more positive affect. Our work indicates NBO may be a fruitful method for probing the role of distinct social cues in eliciting attention in naturalistic social contexts at the individual level.

Theta power relates to infant object encoding in naturalistic mother-infant interactions.

This study investigates infants' neural and behavioral responses to maternal ostensive signals during naturalistic mother-infant interactions and their effects on object encoding. Mothers familiarized their 9- to 10-month-olds (N = 35, 17 females, mainly White, data collection: 2018-2019) with objects with or without mutual gaze, infant-directed speech, and calling the infant's name. Ostensive signals focused infants' attention on objects and their mothers. Infant theta activity synchronized and alpha activity desynchronized during interactions compared to a nonsocial resting phase (Cohen' d: 0.49-0.75). Yet, their amplitudes were unrelated to maternal ostensive signals. Ostensive signals did not facilitate object encoding. However, higher infant theta power during encoding predicted better subsequent object recognition. Results strengthen the role of theta-band power for early learning processes.

Word segmentation from transcriptions of child-directed speech using lexical and sub-lexical cues.

We compare two frameworks for the segmentation of words in child-directed speech, PHOCUS and MULTICUE. PHOCUS is driven by lexical recognition, whereas MULTICUE combines sub-lexical properties to make boundary decisions, representing differing views of speech processing. We replicate these frameworks, perform novel benchmarking and confirm that both achieve competitive results. We develop a new framework for segmentation, the DYnamic Programming MULTIple-cue framework (DYMULTI), which combines the strengths of PHOCUS and MULTICUE by considering both sub-lexical and lexical cues when making boundary decisions. DYMULTI achieves state-of-the-art results and outperforms PHOCUS and MULTICUE on 15 of 26 languages in a cross-lingual experiment. As a model built on psycholinguistic principles, this validates DYMULTI as a robust model for speech segmentation and a contribution to the understanding of language acquisition.

Phonetic variation in English infant-directed speech: A large-scale corpus analysis

Learning sound categories is central to language acquisition – but we know little about the extent of phonetic variability in the learner’s input. In this study, we phonetically annotated coronal segments (/t/, /d/, /s/, /z/, and /n/) in a corpus of naturalistic American English infant-directed speech (IDS). We did not find evidence that IDS is consistently more canonical than adult-directed speech (ADS), challenging the notion of IDS as a learning register. While IDS is not more canonical than ADS overall, the canonical form was nonetheless the most frequent form in IDS for all segments except /t/. We also considered how infants may move beyond the task of identifying the canonical form to how they may learn to cluster allophones; for this purpose, we quantified the dissimilarity in the phonological environments of the variants in question. Lastly, we investigated a case in which the overwhelming majority of instantiations were not canonical – word-final t and d – and demonstrated that morphologically-conditioned suffixes were more canonical than other word final segments. This corpus is a vital step towards understanding how infants can learn to categorize sounds from their input and will be an invaluable tool for future sociolinguistic, computational and theoretical modeling of language learning.

Predicting Age of Acquisition for Children's Early Vocabulary in Five Languages Using Language Model Surprisal.

What makes a word easy to learn? Early-learned words are frequent and tend to name concrete referents. But words typically do not occur in isolation. Some words are predictable from their contexts; others are less so. Here, we investigate whether predictability relates to when children start producing different words (age of acquisition; AoA). We operationalized predictability in terms of a word's surprisal in child-directed speech, computed using n-gram and long-short-term-memory (LSTM) language models. Predictability derived from LSTMs was generally a better predictor than predictability derived from n-gram models. Across five languages, average surprisal was positively correlated with the AoA of predicates and function words but not nouns. Controlling for concreteness and word frequency, more predictable predicates and function words were learned earlier. Differences in predictability between languages were associated with cross-linguistic differences in AoA: the same word (when it was a predicate) was produced earlier in languages where the word was morepredictable.

Early verb production in Nungon.

This brief research report presents a comparison of the early verb productions of four children acquiring the Papuan language Nungon as a first language. A previous case study examined only verb productions of the child TO; these are now compared with those from three other children, studied from ages 1;1-2;7 (non-dense corpus; one child, AB) and ages 2;4-2;7 (dense corpora; two children, MK and MF). Two of the most striking features of TO's early verb productions are shown to be outliers relative to the other three children: her 'root nominals' stage and her delayed near future tense production. Neither of these is transparently linked to patterns in her parents' child-directed speech. The other children also display differing strategies into language production. The dense corpus is beneficial for catching tokens of less-frequent inflections, but the frequent long recording sessions may be difficult for at least one child to tolerate.

The Puss in Boots effect

Abstract 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 exaggerated prosodic qualities or pet-directed speech. We experimentally manipulated eye size in photographs of twelve dog breeds by −15%, +15% and +30%. We first showed that dogs with larger eyes were indeed perceived as younger. We then recorded men and women speaking towards these photographs, who also rated these images for cuteness. Linear mixed-effects models demonstrated that increasing eye size by 15% significantly increased pitch range (f 0 range) and variability (f 0CV) among women only. Cuteness ratings did not vary with eye size, due to a possible ceiling effect across eye sizes. Our results offer preliminary evidence that large eyes can elicit pet-directed speech and suggest that PDS may be modulated by perceived juvenility rather than cuteness. We discuss these findings in the context of inter-species vocal communication.

Relating referential clarity and phonetic clarity in infant-directed speech.

Psycholinguistic research on children's early language environments has revealed many potential challenges for language acquisition. One is that in many cases, referents of linguistic expressions are hard to identify without prior knowledge of the language. Likewise, the speech signal itself varies substantially in clarity, with some productions being very clear, and others being phonetically reduced, even to the point of uninterpretability. In this study, we sought to better characterize the language-learning environment of American English-learning toddlers by testing how well phonetic clarity and referential clarity align in infant-directed speech. Using an existing Human Simulation Paradigm (HSP) corpus with referential transparency measurements and adding new measures of phonetic clarity, we found that the phonetic clarity of words' first mentions significantly predicted referential clarity (how easy it was to guess the intended referent from visual information alone) at that moment. Thus, when parents' speech was especially clear, the referential semantics were also clearer. This suggests that young children could use the phonetics of speech to identify globally valuable instances that support better referential hypotheses, by homing in on clearer instances and filtering out less-clear ones. Such multimodal "gems" offer special opportunities for early word learning. RESEARCH HIGHLIGHTS: In parent-infant interaction, parents' referential intentions are sometimes clear and sometimes unclear; likewise, parents' pronunciation is sometimes clear and sometimes quite difficult to understand. We find that clearer referential instances go along with clearer phonetic instances, more so than expected by chance. Thus, there are globally valuable instances ("gems") from which children could learn about words' pronunciations and words' meanings at the same time. Homing in on clear phonetic instances and filtering out less-clear ones would help children identify these multimodal "gems" during word learning.

Dog brains are sensitive to infant- and dog-directed prosody

When addressing preverbal infants and family dogs, people tend to use specific speech styles. While recent studies suggest acoustic parallels between infant- and dog-directed speech, it is unclear whether dogs, like infants, show enhanced neural sensitivity to prosodic aspects of speech directed to them. Using functional magnetic resonance imaging on awake unrestrained dogs we identify two non-primary auditory regions, one that involve the ventralmost part of the left caudal Sylvian gyrus and the temporal pole and the other at the transition of the left caudal and rostral Sylvian gyrus, which respond more to naturalistic dog- and/or infant-directed speech than to adult-directed speech, especially when speak by female speakers. This activity increase is driven by sensitivity to fundamental frequency mean and variance resulting in positive modulatory effects of these acoustic parameters in both aforementioned non-primary auditory regions. These findings show that the dog auditory cortex, similarly to that of human infants, is sensitive to the acoustic properties of speech directed to non-speaking partners. This increased neuronal responsiveness to exaggerated prosody may be one reason why dogs outperform other animals when processing speech.

The Children's Picture Books Lexicon (CPB-LEX): A large-scale lexical database from children's picture books.

This article presents CPB-LEX, a large-scale database of lexical statistics derived from children's picture books (age range 0-8 years). Such a database is essential for research in psychology, education and computational modelling, where rich details on the vocabulary of early print exposure are required. CPB-LEX was built through an innovative method of computationally extracting lexical information from automatic speech-to-text captions and subtitle tracks generated from social media channels dedicated to reading picture books aloud. It consists of approximately 25,585 types (wordforms) and their frequency norms (raw and Zipf-transformed), a lexicon of bigrams (two-word sequences and their transitional probabilities) and a document-term matrix (which shows the importance of each word in the corpus in each book). Several immediate contributions of CPB-LEX to behavioural science research are reported, including that the new CPB-LEX frequency norms strongly predict age of acquisition and outperform comparable child-input lexical databases. The database allows researchers and practitioners to extract lexical statistics for high-frequency words which can be used to develop word lists. The paper concludes with an investigation of how CPB-LEX can be used to extend recent modelling research on the lexical diversity children receive from picture books in addition to child-directed speech. Our model shows that the vocabulary input from a relatively small number of picture books can dramatically enrich vocabulary exposure from child-directed speech and potentially assist children with vocabulary input deficits. The database is freely available from the Open Science Framework repository: https://tinyurl.com/4este73c .