The development of tone discrimination in infancy: Evidence from a cross-linguistic, multi-lab report.

We report the findings of a multi-language and multi-lab investigation of young infants' ability to discriminate lexical tones as a function of their native language, age and language experience, as well as of tone properties. Given the high prevalence of lexical tones across human languages, understanding lexical tone acquisition is fundamental for comprehensive theories of language learning. While there are some similarities between the developmental course of lexical tone perception and that of vowels and consonants, findings for lexical tones tend to vary greatly across different laboratories. To reconcile these differences and to assess the developmental trajectory of native and non-native perception of tone contrasts, this study employed a single experimental paradigm with the same two pairs of Cantonese tone contrasts (perceptually similar vs. distinct) across 13 laboratories in Asia-Pacific, Europe and North-America testing 5-, 10- and 17-month-old monolingual (tone, pitch-accent, non-tone) and bilingual (tone/non-tone, non-tone/non-tone) infants. Across the age range and language backgrounds, infants who were not exposed to Cantonese showed robust discrimination of the two non-native lexical tone contrasts. Contrary to this overall finding, the statistical model assessing native discrimination by Cantonese-learning infants failed to yield significant effects. These findings indicate that lexical tone sensitivity is maintained from 5 to 17 months in infants acquiring tone and non-tone languages, challenging the generalisability of the existing theoretical accounts of perceptual narrowing in the first months of life. RESEARCH HIGHLIGHTS: This is a multi-language and multi-lab investigation of young infants' ability to discriminate lexical tones. This study included data from 13 laboratories testing 5-, 10-, and 17-month-old monolingual (tone, pitch-accent, non-tone) and bilingual (tone/non-tone, non-tone/non-tone) infants. Overall, infants discriminated a perceptually similar and a distinct non-native tone contrast, although there was no evidence of a native tone-language advantage in discrimination. These results demonstrate maintenance of tone discrimination throughout development.

Relating the prosody of infant-directed speech to children's vocabulary size.

This study examines correlations between the prosody of infant-directed speech (IDS) and children's vocabulary size. We collected longitudinal speech data and vocabulary information from Dutch mother-child dyads with children aged 18 (N = 49) and 24 (N = 27) months old. We took speech context into consideration and distinguished between prosody when mothers introduce familiar vs. unfamiliar words to their children. The results show that IDS mean pitch predicts children's vocabulary growth between 18 and 24 months. In addition, the degree of prosodic modification when mothers introduce unfamiliar words to their children correlates with children's vocabulary growth during this period. These findings suggest that the prosody of IDS, especially in word-learning contexts, may serve linguistic purposes.

Examining Dutch children's vocabularies across infancy and toddlerhood: Demographic effects are age-specific and task-specific.

Limited studies have examined demographic differences in children's vocabulary in longitudinal samples, while there are questions regarding the duration, direction, and magnitude of these effects across development. In this longitudinal study, we included over 400 Dutch children. Caregivers filled out N-CDIs when children were 9-11 months (measuring word comprehension, word production, and gestures) and around 2-5 years of age (measuring word production). At 2-5 years, we also administered a receptive vocabulary task in the lab. We examined demographic effects on vocabulary size across infancy and toddlerhood. We found a disadvantage for males in infants' gestures and toddlers' vocabulary production. We found a negative effect of maternal education on infants' caregiver-reported vocabulary, but a positive effect on toddlers' lab-administered receptive vocabulary. Lastly, we found a negative effect of multilingualism - but only for the lab-administered task. Examining predictors in large, longitudinal samples ensures their robustness and generalisability across development.

Avoiding stress on non-lexical material in nouns and verbs: predictable verb prosody in Serbo-Croatian stress standard varieties.

We consider two asymmetries reported in the literature on word prosodic systems: the tendency to allow more prosodic contrast in nouns than in verbs and the tendency to avoid stress on functional material. We focus on the interaction between these two tendencies and propose a formal mechanism to handle this interaction couched in Optimality Theory. In a case study on a group of standard Serbo-Croatian varieties that have predictable stress in verbs but contrastive stress in nouns, we develop an analysis of predictable and morphologically conditioned stress assignment. Our analysis features a family of constraints militating against stress on non-lexical material on three different levels: stress on inflection proper (*Infl-Stress-1), stress on non-lexical material in the locality domain of inflection (*Infl-Stress-2), and stress on non-lexical material altogether (*Infl-Stress-3). Analyzing a class of prosodically exceptional denominal and borrowed verbs, we show that lexical-category effects exist between and within categories: denominal verbs allow exceptional preservation of nominal stress, which leads to additional prosodic contrast in this class of verbs. Finally, we explore the option of subsuming exceptionally contrast-preserving borrowed verbs under denominal verbs, offering arguments in favor of the hotly debated view from the literature that verbs are universally borrowed as denominal.

Lexical and Prosodic Pitch Modifications in Cantonese Infant-directed Speech.

The functions of acoustic-phonetic modifications in infant-directed speech (IDS) remain a question: do they specifically serve to facilitate language learning via enhanced phonemic contrasts (the hyperarticulation hypothesis) or primarily to improve communication via prosodic exaggeration (the prosodic hypothesis)? The study of lexical tones provides a unique opportunity to shed light on this, as lexical tones are phonemically contrastive, yet their primary cue, pitch, is also a prosodic cue. This study investigated Cantonese IDS and found increased intra-talker variation of lexical tones, which more likely posed a challenge to rather than facilitated phonetic learning. Although tonal space was expanded which could facilitate phonetic learning, its expansion was a function of overall intonational modifications. Similar findings were observed in speech to pets who should not benefit from larger phonemic distinction. We conclude that lexical-tone adjustments in IDS mainly serve to broadly enhance communication rather than specifically increase phonemic contrast for learners.

Pitch properties of infant-directed speech specific to word-learning contexts: a cross-linguistic investigation of Mandarin Chinese and Dutch.

This study investigates the pitch properties of infant-directed speech (IDS) specific to word-learning contexts in which mothers introduce unfamiliar words to children. Using a semi-spontaneous story-book telling task, we examined (1) whether mothers made distinctions between unfamiliar and familiar words with pitch in IDS compared to adult-directed speech (ADS); (2) whether pitch properties change when mothers address children from 18 to 24 months; and (3) how Mandarin Chinese and Dutch IDS differ in their pitch properties in word-learning contexts. Results show that the mean pitch of Mandarin Chinese IDS was already ADS-like when children were 24 months, but Dutch IDS remained exaggerated in pitch at the same age. Crucially, Mandarin Chinese mothers used a higher pitch and a larger pitch range in IDS when introducing unfamiliar words, while Dutch mothers used a higher pitch specifically for familiar words. These findings contribute to the language-specificity of prosodic input in early lexical development.

Statistical learning of speech sounds is most robust during the period of perceptual attunement.

Although statistical learning has been shown to be a domain-general mechanism, its constraints, such as its interactions with perceptual development, are less well understood and discussed. This study is among the first to investigate the distributional learning of lexical pitch in non-tone-language-learning infants, exploring its interaction with language-specific perceptual attunement during the first 2years after birth. A total of 88 normally developing Dutch infants of 5, 11, and 14months were tested via a distributional learning paradigm and were familiarized on a unimodal or bimodal distribution of high-level versus high-falling tones in Mandarin Chinese. After familiarization, they were tested on a tonal contrast that shared equal distributional information in either modality. At 5months, infants in both conditions discriminated the contrast, whereas 11-month-olds showed discrimination only in the bimodal condition. By 14months, infants failed to discriminate the contrast in either condition. Results indicate interplay between infants' long-term linguistic experience throughout development and short-term distributional learning during the experiment, and they suggest that the influence of tonal distributional learning varies along the perceptual attunement trajectory, such that opportunities for distributional learning effects appear to be constrained in the beginning and at the end of perceptual attunement. The current study contributes to previous research by demonstrating an effect of age on learning from distributional cues.

Enhanced music sensitivity in 9-month-old bilingual infants.

This study explores the influence of bilingualism on the cognitive processing of language and music. Specifically, we investigate how infants learning a non-tone language perceive linguistic and musical pitch and how bilingualism affects cross-domain pitch perception. Dutch monolingual and bilingual infants of 8-9 months participated in the study. All infants had Dutch as one of the first languages. The other first languages, varying among bilingual families, were not tone or pitch accent languages. In two experiments, infants were tested on the discrimination of a lexical (N = 42) or a violin (N = 48) pitch contrast via a visual habituation paradigm. The two contrasts shared identical pitch contours but differed in timbre. Non-tone language learning infants did not discriminate the lexical contrast regardless of their ambient language environment. When perceiving the violin contrast, bilingual but not monolingual infants demonstrated robust discrimination. We attribute bilingual infants' heightened sensitivity in the musical domain to the enhanced acoustic sensitivity stemming from a bilingual environment. The distinct perceptual patterns between language and music and the influence of acoustic salience on perception suggest processing diversion and association in the first year of life. Results indicate that the perception of music may entail both shared neural network with language processing, and unique neural network that is distinct from other cognitive functions.

Categorical phonotactic knowledge filters second language input, but probabilistic phonotactic knowledge can still be acquired.

Probabilistic phonotactic knowledge facilitates perception, but categorical phonotactic illegality can cause misperceptions, especially of non-native phoneme combinations. If misperceptions induced by first language (L1) knowledge filter second language input, access to second language (L2) probabilistic phonotactics is potentially blocked for L2 acquisition. The facilitatory effects of L2 probabilistic phonotactics and categorical filtering effects of L1 phonotactics were compared and contrasted in a series of cross-modal priming experiments. Dutch native listeners and L1 Spanish and Japanese learners of Dutch had to perform a lexical decision task on Dutch words that started with /sC/ clusters that were of different degrees of probabilistic wellformedness in Dutch but illegal in Spanish and Japanese. Versions of target words with Spanish illegality resolving epenthesis in the clusters primed the Spanish group, showing an L1 filter; a similar effect was not found for the Japanese group. In addition, words with wellformed /sC/ clusters were recognised faster, showing a positive effect on processing of probabilistic wellformedness. However, Spanish learners with higher proficiency were facilitated to a greater extent by wellformed but epenthesised clusters, showing that although probabilistic learning occurs in spite of the L1 filter, the acquired probabilistic knowledge is still affected by L1 categorical knowledge. Categorical phonotactic and probabilistic knowledge are of a different nature and interact in acquisition.

Infants' behaviours elicit different verbal, nonverbal, and multimodal responses from caregivers during early play.

Caregivers use a range of verbal and nonverbal behaviours when responding to their infants. Previous studies have typically focused on the role of the caregiver in providing verbal responses, while communication is inherently multimodal (involving audio and visual information) and bidirectional (exchange of information between infant and caregiver). In this paper, we present a comprehensive study of caregivers' verbal, nonverbal, and multimodal responses to 10-month-old infants' vocalisations and gestures during free play. A new coding scheme was used to annotate 2036 infant vocalisations and gestures of which 87.1 % received a caregiver response. Most caregiver responses were verbal, but 39.7 % of all responses were multimodal. We also examined whether different infant behaviours elicited different responses from caregivers. Infant bimodal (i.e., vocal-gestural combination) behaviours elicited high rates of verbal responses and high rates of multimodal responses, while infant gestures elicited high rates of nonverbal responses. We also found that the types of verbal and nonverbal responses differed as a function of infant behaviour. The results indicate that infants influence the rates and types of responses they receive from caregivers. When examining caregiver-child interactions, analysing caregivers' verbal responses alone undermines the multimodal richness and bidirectionality of early communication.

Prosodic input and children's word learning in infant- and adult-directed speech.

This study examines (1) whether infant-directed speech (IDS) facilitates children's word learning compared to adult-directed speech (ADS); and (2) the link between the prosody of IDS in word-learning contexts and children's word learning from ADS and IDS. Twenty-four Dutch mother-child dyads participated when children were 18 and 24 months old. We collect mothers' ADS and IDS at both ages and test children's word learning from ADS and IDS at 24 months. We find that Dutch 24-month-old children could reliably learn novel words from both ADS and IDS, and IDS had a facilitative effect. In addition, children's word learning from IDS (but not ADS) is predicted by IDS pitch range when mothers introduce unfamiliar words to children at 18 months. Our findings contribute to an understanding of the role of IDS prosody in language development, highlighting both individual differences and contextual differences in IDS prosody.

The ability to use contextual cues to achieve phonological constancy emerges by 14 months.

The ability to map similar sounding words to different meanings alone is far from enough for successful speech processing. To overcome variability in the speech signal, young learners must also recognize words across surface variations. Previous studies have shown that infants at 14 months are able to use variations in word-internal cues (i.e., acoustic cues within the target word) to form phonological categories and to learn words. The present study takes into consideration the fact that talker variability can easily lead to acoustic overlap between phonological categories, in which case reliance on word-external cues (i.e., acoustic cues in the context preceding and/or following the target word, also referred to as contextual cues) as a frame of reference is obligatory for successful talker adaptation. In a series of experiments, the present study examines when infants are able to use word-external cues to tune to different talkers for the benefit of word learning. Cantonese-learning 14-month-old, 18-month-old, and 24-month-old infants (N = 258) were tested on the associative learning of Cantonese Tone 1-Tone 3 contrast. Results showed that talker variability that yielded acoustic overlap between the two tonal categories compromised infants' ability to map the contrast onto word meanings. However, when given speaker-matched contextual cues, infants as young as 14 months of age demonstrated a certain degree of talker adaptation which may have subserved their use of phonetic details in novel word learning. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Effect of Complexity on Speech Sound Development: Evidence From Meta-Analysis Review of Treatment-Based Studies.

In the current study, we aimed at understanding the effect of exposure to complex input on speech sound development, by conducting a systematic meta-analysis review of the existing treatment-based studies employing complex input in children with speech sound disorders. In the meta-analysis review, using a list of inclusion criteria, we narrowed 280 studies down to 12 studies. Data from these studies were extracted to calculate effect sizes that were plotted as forest plots to determine the efficacy of complexity-based treatment approaches. The outcome variables of interest were improvement on the treated and generalization to the untreated sounds. Meta-analysis revealed that the exposure to complex input not only promoted improvement in production of complex speech sounds (d = 1.08, CI = 0.98-1.19) but also facilitated the production of untreated simple speech sounds (d = 2.69, CI = 1.98-3.54). Overall, the current findings revealed that the exposure to complex input promotes acquisition of both complex and simple speech sounds. The current findings are in line with the models of language learnability. The current findings have implications in the treatment of speech sound disorders.

Linking Variation in Perception and Production in Sound Change: Evidence from Dutch Obstruent Devoicing.

This study investigates the link between the perception and production in sound change in progress, both at the regional and the individual level. Two devoicing processes showing regional variation in Dutch are studied: the devoicing of initial labiodental fricatives and of initial bilabial stops. Five regions were selected, to represent different stages of change in progress. For each region, 20 participants took part in production (Study 1) and perception (Study 2) experiments. First, the results of the production tasks give additional insight in the regional and individual patterns of sound change. Second, the regional perceptual patterns in fricatives match the differences in production: perception is the most categorical in regions where the devoicing process is starting, and the least categorical in regions where the process of devoicing is almost completed. Finally, a clear link is observed between the production and perception systems undergoing sound change at the individual level. Changes in the perceptual system seem to precede changes in production. However, at the sound change completion, perception lags behind: individuals still perceive a contrast they no longer produce.

Complexity drives speech sound development: Evidence from artificial language training.

Traditionally, learning is assumed to take place with exposure to simpler elements first followed by exposure to elements with increasing levels of difficulty. Recent reports suggest that exposure to complex elements leads to more widespread changes. However, whether learning via exposure to complex or to simple elements is more beneficial is a matter of ongoing debate. In the current study, using behavioral and electrophysiological measures, we aimed at understanding this by comparing subjects trained with complex speech sounds with those trained with simple speech sounds in a 5-day pseudoword-picture training paradigm. We found that though the subjects learned both complex and simple speech sounds to similar degrees, subjects who were trained with complex stimuli demonstrated more generalizations to novel complex and simple stimuli, whereas those trained with simple stimuli exhibited generalization only to simple but not to complex stimuli (Experiment 1). Along with behavioral measures, using mismatch negativity, we found that training with complex stimuli can lead to more extensive neural changes for both complex and simple stimuli as compared with training with simple stimuli (Experiment 2). In artificial language learning, learning with complex stimuli appears to be more effective than training with simple stimuli as far as generalization is concerned. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

How Do Infants Disaggregate Referential and Affective Pitch?

Infants are faced with a challenge of disaggregating functions of pitch in the ambient language into affective, pragmatic or referential (the latter in tone languages only). This mini review discusses several factors that might facilitate the disaggregation of referential and affective pitch in infancy: acoustic characteristics of infant-directed speech, recognition of vocal affect, facial cues accompanying affective prosody, and lateralization of affective and referential prosody in the brain. It proposes two hypotheses concerning the role of audiovisual cues and brain lateralization.

Monolingual and Bilingual Infants' Ability to Use Non-native Tone for Word Learning Deteriorates by the Second Year After Birth.

Previous studies reported a non-native word learning advantage for bilingual infants at around 18 months. We investigated developmental changes in infant interpretation of sounds that aid in object mapping. Dutch monolingual and bilingual (exposed to Dutch and a second non-tone-language) infants' word learning ability was examined on two novel label-object pairings using syllables differing in Mandarin tones as labels (flat vs. falling). Infants aged 14-15 months, regardless of language backgrounds, were sensitive to violations in the label-objects pairings when lexical tones were switched compared to when they were the same as habituated. Conversely at 17-18 months, neither monolingual nor bilingual infants demonstrated learning. Linking with existing literature, infants' ability to associate non-native tones with meanings may be related to tonal acoustic properties and/or perceptual assimilation to native prosodic categories. These findings provide new insights into the relation between infant tone perception, learning, and interpretative narrowing from a developmental perspective.

Lexical Tones in Mandarin Chinese Infant-Directed Speech: Age-Related Changes in the Second Year of Life.

Tonal information is essential to early word learning in tone languages. Although numerous studies have investigated the intonational and segmental properties of infant-directed speech (IDS), only a few studies have explored the properties of lexical tones in IDS. These studies mostly focused on the first year of life; thus little is known about how lexical tones in IDS change as children's vocabulary acquisition accelerates in the second year (Goldfield and Reznick, 1990; Bloom, 2001). The present study examines whether Mandarin Chinese mothers hyperarticulate lexical tones in IDS addressing 18- and 24-month-old children-at which age children are learning words at a rapid speed-vs. adult-directed speech (ADS). Thirty-nine Mandarin Chinese-speaking mothers were tested in a semi-spontaneous picture-book-reading task, in which they told the same story to their child (IDS condition) and to an adult (ADS condition). Results for the F0 measurements (minimum F0, maximum F0, and F0 range) of tone in the speech data revealed a continuum of differences among IDS addressing 18-month-olds, IDS addressing 24-month-olds, and ADS. Lexical tones in IDS addressing 18-month-old children had a higher minimum F0, higher maximum F0, and larger pitch range than lexical tones in ADS. Lexical tones in IDS addressing 24-month-old children showed more similarity to ADS tones with respect to pitch height: there were no differences in minimum F0 and maximum F0 between ADS and IDS. However, F0 range was still larger. These results suggest that lexical tones are generally hyperarticulated in Mandarin Chinese IDS addressing 18- and 24- month-old children despite the change in pitch level over time. Mandarin Chinese mothers hyperarticulate lexical tones in IDS when talking to toddlers and potentially facilitate tone acquisition and word learning.

Pitch Perception in the First Year of Life, a Comparison of Lexical Tones and Musical Pitch.

Pitch variation is pervasive in speech, regardless of the language to which infants are exposed. Lexical tone is influenced by general sensitivity to pitch. We examined whether the development in lexical tone perception may develop in parallel with perception of pitch in other cognitive domains namely music. Using a visual fixation paradigm, 100 and one 4- and 12-month-old Dutch infants were tested on their discrimination of Chinese rising and dipping lexical tones as well as comparable three-note musical pitch contours. The 4-month-old infants failed to show a discrimination effect in either condition, whereas the 12-month-old infants succeeded in both conditions. These results suggest that lexical tone perception may reflect and relate to general pitch perception abilities, which may serve as a basis for developing more complex language and musical skills.

Prosody in birdsong: A review and perspective.

Birdsong shows striking parallels with human speech. Previous comparisons between birdsong and human vocalizations focused on syntax, phonology and phonetics. In this review, we propose that future comparative research should expand its focus to include prosody, i.e. the temporal and melodic properties that extend over larger units of song. To this end, we consider the similarities between birdsong structure and the prosodic hierarchy in human speech and between context-dependent acoustic variations in birdsong and the biological codes in human speech. Moreover, we discuss songbirds' sensitivity to prosody-like acoustic features and the role of such features in song segmentation and song learning in relation to infants' sensitivity to prosody and the role of prosody in early language acquisition. Finally, we make suggestions for future comparative birdsong research, including a framework of how prosody in birdsong can be studied. In particular, we propose to analyze birdsong as a multidimensional signal composed of specific acoustic features, and to assess whether these acoustic features are organized into prosody-like structures.