Phonological pattern frequency and speech production in adults and children

Learning a language with vowelless words

Vowelless words are exceptionally typologically rare, though they are found in some languages, such as Tashlhiyt (e.g., fkt 'give it'). The current study tests whether lexicons containing tri-segmental (CCC) vowelless words are more difficult to acquire than lexicons not containing vowelless words by adult English speakers from brief auditory exposure. The role of acoustic-phonetic form on learning these typologically rare word forms is also explored: In Experiment 1, participants were trained on words produced in either only Clear speech or Casual speech productions of words; Experiment 2 trained participants on lexical items produced in both speech styles. Listeners were able to learn both vowelless and voweled lexicons equally well when speaking style was consistent for participants, but learning was lower for vowelless lexicons when training consisted of variable acoustic-phonetic forms. In both experiments, responses to a post-training wordlikeness ratings task containing novel items revealed that exposure to a vowelless lexicon leads participants to accept new vowelless words as acceptable lexical forms. These results demonstrate that one of the typologically rarest types of lexical forms - words without vowels - can be rapidly acquired by naive adult listeners. Yet, acoustic-phonetic variation modulates learning.

Integrated sentence-level speech perception evokes strengthened language networks and facilitates early speech development

Natural poetic speeches (i.e., proverbs, nursery rhymes, and commercial ads) with strong prosodic regularities are easily memorized by children and the harmonious acoustic patterns are suggested to facilitate their integrated sentence processing. Do children have specific neural pathways for perceiving such poetic utterances, and does their speech development benefit from it? We recorded the task-induced hemodynamic changes of 94 children aged 2 to 12 years using functional near-infrared spectroscopy (fNIRS) while they listened to poetic and non-poetic natural sentences. Seventy-three adult as controls were recruited to investigate the developmental specificity of children group. The results indicated that poetic sentences perceiving is a highly integrated process featured by a lower brain workload in both groups. However, an early activated large-scale network was induced only in the child group, coordinated by hubs for connectivity diversity. Additionally, poetic speeches evoked activation in the phonological encoding regions in the children's group rather than adult controls which decreases with children's ages. The neural responses to poetic speeches were positively linked to children's speech communication performance, especially the fluency and semantic aspects. These results reveal children's neural sensitivity to integrated speech perception which facilitate early speech development by strengthening more sophisticated language networks and the perception-production circuit.

Rate of Stuttering and Factors Associated With Speech Fluency Characteristics in Adult Struggling Readers

Stuttering is a disorder that affects about 1% of the population and manifests as speech disfluencies. Reading difficulties and disabilities are commonly found in this population. Nonetheless, speech disfluencies have not been explored in adult struggling readers (ASRs). In the current study, we examined the rate of stuttering in ASRs as well as the relationships between their speech fluency and reading skills. A total of 120 participants were interviewed about their experiences with reading and administered standardized reading and reading-related assessments. Speech fluency and the criterion for stuttering were based on the interview. About 18.3% of the sample met the criterion for stuttering. ASRs who stutter (ASRs-S) and ASRs who do not stutter (ASRs-NS) did not differ in their reading and reading-related skills. ASRs-S had higher rates of negative correlations between reading and reading-related skills compared with ASRs-NS. Correlation patterns between performance on standardized assessments point to higher rates of uneven skills or dissociations in ASRs-S. These findings may have implications for the assessment and instruction for ASRs.

Novel phonotactic learning by children and infants: Generalizing syllable-position but not co-occurrence regularities

Restrictions in the sequencing of sounds (phonotactic constraints) can be represented at the level of sound co-occurrences (e.g., in baF.Pev, F and P co-occur) and at the level of the syllable (e.g., F is syllable-coda/end, P is syllable-onset/start). Can children (5-year-olds) and infants (11-month-olds) represent constraints as sound co-occurrences and/or relative to syllable positions? Participants listened to artificial languages displaying both word-medial consonant restrictions in co-occurrence pairs (e.g., FP or DZ but not FZ) and in the position of consonants within syllables (e.g., P/Z onsets and D/F codas) in words like baF.Pev and tiD.Zek. Children responded similarly to novel words with the same (e.g., FP) versus different (e.g., FZ) co-occurrence pairs, but they were more misled (i.e., responded "heard it before") by novel words with consonants in the same (e.g., onset-P) versus different (e.g., coda-P) syllable positions (Experiment 1). With the same training stimuli, infants had similar orientation times for novel words with the same versus different co-occurrence pairs, but they had longer orientation times for novel words with consonants in the same versus different syllable positions (Experiment 2). Thus, across different methods and ages, syllable-position information was more readily available for generalization than consonant co-occurrence information. The results suggest that when multiple regularities are present simultaneously, some phonotactic constraints (e.g., consonants in particular syllable positions) may be spontaneously represented and generalized by children and infants, whereas others (e.g., consonant co-occurrences) might not be available. The results contribute toward understanding how children and infants represent sound sequences.

Consonant Age of Acquisition Reveals Nonlinear Effects in Nonword Repetition Performance

Recent work has shown significant sublexical effects of long-term memory in nonword repetition (NWR) using a dichotomous consonant age of acquisition (CAoA) variable (Moore, 2018; Moore, Fiez, and Tompkins, 2017). Performance consistently decreased when stimuli comprised consonants acquired later versus earlier in speech development. To address potential confounds related to stimulus design and linearity, the purpose of this study was to test whether performance decreases as the CAoA value of stimuli increases in various linguistic tasks using a continuous CAoA variable. Thirty-one college students completed NWR and other linguistic tasks in which the stimuli varied in average CAoA values. Data were analyzed using multilevel modeling. After accounting for phonotactic probability, CAoA was a statistically significant predictor of performance across the models reported. The relationship was more complex in some of the models in which CAoA showed a statistically significant nonlinear relationship with the outcome measure. Results from this study support previous work showing that CAoA affects performance on NWR and other linguistic tasks that vary in their memory, auditory perceptual, and articulatory demands. Importantly, this line of work was extended here by demonstrating that the CAoA effect is robust across novel stimulus sets and study designs, and may be more complex than previously understood when using a dichotomous CAoA variable. Quadratic results suggest that the CAoA variable has a differential effect on performance for low to moderate CAoA values, but for higher CAoA values the effect is similarly negative. The nonlinear relationship between CAoA and measures of speed and accuracy on some of the tasks warrants further study into the complex relationship between various predictive factors that contribute to language performance.

Speech Errors in the Production of Initial Consonant Clusters: The Roles of Frequency and Sonority

PURPOSE

One of the central questions in speech production research is to what degree certain structures have an inherent difficulty and to what degree repeated encounter and practice make them easier to process. The goal of this article was to determine the extent to which frequency and sonority distance of consonant clusters predict production difficulties.

METHOD

We used a tongue twister paradigm to elicit speech errors on syllable-initial German consonant clusters and investigated the relative influences of cluster frequency and sonority distance between the consonants of a cluster on production accuracy. Native speakers of German produced pairs of monosyllabic pseudowords beginning with consonant clusters at a high speech rate.

RESULTS

Error rates decreased with increasing frequency of the consonant clusters. A high sonority distance, on the other hand, did not facilitate a cluster's production, but speech errors led to optimized sonority structure for a subgroup of clusters. In addition, the combination of consonant clusters in a stimulus pair has a great impact on production accuracy.

CONCLUSION

These results suggest that both frequency of use and sonority distance codetermine production ease, as well as syntagmatic competition between adjacent sound sequences.

Predicting Which Children Will Normalize Without Intervention for Speech Sound Disorders

PURPOSE

The speech of some children does not follow a typical normalization trajectory, and they develop speech sound disorders (SSD). This study investigated predictive correlates of speech sound normalization in children who were at risk of SSD.

METHOD

A prospective population cohort study of 845 Cantonese-speaking preschoolers was conducted over 2.5 years to examine (a) children who resolved nonadult realizations of consonants (normalized) and (b) those who had persisting speech sound difficulties (did not normalize). From these 845, a sample of 82 participants characterized as having SSD (1.25 SDs below the mean in a standardized speech assessment, with a delay in initial consonant acquisition or with one or more atypical errors) was followed for 2 years at 6-month intervals or until the completion of their initial consonant inventory. Data from 43 children who did not receive speech-language pathology services were analyzed with survival analysis to model time to normalization while controlling for covariates. The target event (outcome) was the completion of their initial consonant inventory.

RESULTS

Under the no-intervention condition, the estimated median time to normalization was 6.59 years of age. Children who were more likely to normalize or normalized in a shorter time were stimulable to all errors and more intelligible as rated by caregivers using the Intelligibility in Context Scale. Those who showed atypical error patterns did not necessarily take longer to normalize. Similarly, expressive language ability was not significantly associated with speech normalization.

CONCLUSIONS

Stimulability and intelligibility were more useful prognostic factors of speech normalization when compared to (a)typicality of error patterns and expressive language ability. Children with low intelligibility and poor stimulability should be prioritized for speech-language pathology services given that their speech errors are less likely to resolve naturally.

Languages are efficient, but for whom?

Human languages evolve to make communication more efficient. But efficiency creates trade-offs: what is efficient for speakers is not always efficient for comprehenders. How do languages balance these competing pressures? We focus on Zipf's meaning-frequency law, the observation that frequent wordforms have more meanings. On the one hand, this law could reflect a speaker-oriented pressure to reuse frequent wordforms. Yet human languages still maintain thousands of distinct wordforms, suggesting a countervailing, comprehender-oriented pressure. What balance of these pressures produces Zipf's meaning-frequency law? Using a neutral baseline, we find that frequent wordforms in real lexica have fewer homophones than predicted by their phonotactic structure: real lexica favor a comprehender-oriented pressure to reduce the cost of frequent disambiguation. These results help clarify the evolutionary drive for efficiency: human languages are subject to competing pressures for efficient communication, the relative magnitudes of which reveal how individual-level cognitive constraints shape languages over time.

Morpho-Phonetic Effects in Speech Production: Modeling the Acoustic Duration of English Derived Words With Linear Discriminative Learning

Recent evidence for the influence of morphological structure on the phonetic output goes unexplained by established models of speech production and by theories of the morphology-phonology interaction. Linear discriminative learning (LDL) is a recent computational approach in which such effects can be expected. We predict the acoustic duration of 4,530 English derivative tokens with the morphological functions DIS, NESS, LESS, ATION, and IZE in natural speech data by using predictors derived from a linear discriminative learning network. We find that the network is accurate in learning speech production and comprehension, and that the measures derived from it are successful in predicting duration. For example, words are lengthened when the semantic support of the word's predicted articulatory path is stronger. Importantly, differences between morphological categories emerge naturally from the network, even when no morphological information is provided. The results imply that morphological effects on duration can be explained without postulating theoretical units like the morpheme, and they provide further evidence that LDL is a promising alternative for modeling speech production.

Paradigmatic enhancement of stem vowels in regular English inflected verb forms

Many theories of word structure in linguistics and morphological processing in cognitive psychology are grounded in a compositional perspective on the (mental) lexicon in which complex words are built up during speech production from sublexical elements such as morphemes, stems, and exponents. When combined with the hypothesis that storage in the lexicon is restricted to the irregular, the prediction follows that properties specific to regular inflected words cannot co-determine the phonetic realization of these inflected words. This study shows that the stem vowels of regular English inflected verb forms that are more frequent in their paradigm are produced with more enhanced articulatory gestures in the midsaggital plane, challenging compositional models of lexical processing. The effect of paradigmatic probability dovetails well with the Paradigmatic Enhancement Hypothesis and is consistent with a growing body of research indicating that the whole is more than its parts.

A lexical advantage in four-year-old children's word repetition

This study examined a potential lexicality advantage in young children's early speech production: do children produce sound sequences less accurately in nonwords than real words? Children aged 3;3-4;4 completed two tasks: a real word repetition task and a corresponding nonword repetition task. Each of the 23 real words had a paired consonant-vowel sequence in the nonword in word-initial position (e.g., 'su' in ['sutkes] 'suitcase' and ['sudrɑs]). The word-initial consonant-vowel sequences were kept constant between the paired words. Previous work on this topic compared different sequences of paired sounds, making it hard to determine if those results were due to a lexical or phonetic effect. Our results show that children reliably produced consonant-vowel sequences in real words more accurately than nonwords. The effect was most pronounced in children with smaller receptive vocabularies. Together, these results reinforce theories arguing for interactions between vocabulary size and phonology in language development.

A Framework of Motoric Complexity: An Investigation in Children With Typical and Impaired Speech Development

Introduction The current work presents a framework of motoric complexity where stimuli differ according to movement elements across a sound sequence (i.e., consonant transitions and vowel direction). This framework was then examined in children with childhood apraxia of speech (CAS), other speech sound disorders (SSDs), and typical development (TD). Method Twenty-four children (CAS, n = 8; SSD, n = 8; TD, n = 8), 5-6 years of age, participated in this study. The children produced words that varied in motoric complexity while transcription, acoustic, and kinematic data were collected. Multidimensional analyses were conducted to examine speech production accuracy, speech motor variability, and temporal control. Results Analyses revealed poorer accuracy, longer movement duration, and greater speech motor variability in children with CAS than TD (across all measures) and other SSDs (accuracy and variability). All children demonstrated greater speech motor variability and longer duration as movement demands increased within the framework of motoric complexity. Diagnostic grouping did not mediate performance on this task. Conclusions Results of this study are believed to reveal gradations of complexity with increasing movement demands, thereby supporting the proposed framework of motoric complexity. This work also supports the importance of considering motoric properties of sound sequences when evaluating speech production skills and designing experimental and treatment stimuli.

Why do human languages have homophones?

Human languages are replete with ambiguity. This is most evident in homophony--where two or more words sound the same, but carry distinct meanings. For example, the wordform "bark" can denote either the sound produced by a dog or the protective outer sheath of a tree trunk. Why would a system evolved for efficient, effective communication display rampant ambiguity? Some accounts argue that ambiguity is actually a design feature of human communication systems, allowing languages to recycle their most optimal wordforms (those which are short, frequent, and phonotactically well-formed) for multiple meanings. We test this claim by constructing five series of artificial lexica matched for the phonotactics and distribution of word lengths found in five real languages (English, German, Dutch, French, and Japanese), and comparing both the quantity and concentration of homophony across the real and artificial lexica. Surprisingly, we find that the artificial lexica exhibit higher upper-bounds on homophony than their real counterparts, and that homophony is even more likely to be found among short, phonotactically plausible wordforms in the artificial than in the real lexica. These results suggest that homophony in real languages is not directly selected for, but rather, that it emerges as a natural consequence of other features of a language. In fact, homophony may even be selected against in real languages, producing lexica that better conform to other requirements of humans who need to use them. Finally, we explore the hypothesis that this is achieved by "smoothing" out dense concentrations of homophones across lexical neighborhoods, resulting in comparatively more minimal pairs in real lexica.

How the Study of Speech Motor Control Can Inform Assessment and Intervention in Childhood Apraxia of Speech

Purpose

The study of speech motor control has led to great advancements in the current understanding of childhood apraxia of speech (CAS). There remains a significant need to bridge the gap between theory and practice to fully understand the clinical implications of past research.

Method

This review article reviews the speech motor control research in CAS and discusses how these works have offered key information about the underlying motor deficits (Grigos et al., 2015; Terband et al., 2019), the influence of structured practice on speech performance (Case & Grigos, 2016; Grigos & Case, 2018), and the role of task complexity (Case, 2019; Case & Grigos, 2016; Grigos & Case, 2018). We highlight salient points from this existing literature and clinical implications to the assessment and treatment of CAS.

Conclusion

The study of speech motor control has shed light on a number of key factors related to CAS. Even within perceptually accurate speech, children with CAS display differences in movement patterning and timing control. Assessment must aim to more directly tax speech motor skills to obtain a thorough and accurate illustration of production deficits. Intervention is challenged with the task of not only improving production accuracy but also facilitating more efficient motor planning and programming. Motor-based intervention that applies motor learning principles and introduces variability across motor, phonetic, and prosodic contexts is believed to achieve this goal, though research is needed to better understand changes in speech motor control with treatment.

Relationship between early phonological processing and later phonological awareness: Evidence from nonword repetition

This study investigated whether individual differences in vocabulary size, speech perception and production, and nonword repetition in 2½ to 3-year-old children predicted phonological awareness two years later. One hundred twenty-two children were tested twice. During the first testing period, we measured children's receptive vocabulary, speech perception, nonword repetition, and articulation. At the second testing period, we measured children's phonological awareness. The best predictors of phonological awareness at age 5 were receptive vocabulary and a measure of phonological processing derived from performance on the nonword repetition task. The results of this study suggest that nonword repetition accuracy can be used to index implicit phonological awareness at an age when children are too young to perform explicit phonological awareness tasks reliably.

Frequencies in Perception and Production Differentially Affect Child Speech

PURPOSE

Frequent sounds and frequent words are both acquired at an earlier age and are produced by children more accurately. Recent research suggests that frequency is not always a facilitative concept, however. Interactions between input frequency in perception and practice frequency in production may limit or inhibit growth. In this study, we consider how a range of input frequencies affect production accuracy and referent identification.

METHOD

Thirty-three typically developing 3- and 4-year-olds participated in a novel word-learning task. In the initial test block, participants heard nonwords 1, 3, 6, or 10 times-produced either by a single talker or by multiple talkers-and then produced them immediately. In a posttest, participants heard all nonwords just once and then produced them. Referent identification was probed in between the test and posttest.

RESULTS

Production accuracy was most clearly facilitated by an input frequency of 3 during the test block. Input frequency interacted with production practice, and the facilitative effect of input frequency did not carry over to the posttest. Talker variability did not affect accuracy, regardless of input frequency. The referent identification results did not favor talker variability or a particular input frequency value, but participants were able to learn the words at better than chance levels.

CONCLUSIONS

The results confirm that the input can be facilitative, but input frequency and production practice interact in ways that limit input-based learning, and more input is not always better. Future research on this interaction may allow clinicians to optimize various types of frequency commonly used during therapy.

Pseudowords to phonological therapy validated by expert judges

PURPOSE

Create a pseudowords list based on favorable environments and submit this to the judgment of expert judges, to obtain a validated list of pseudowords that can be used in therapy.

METHODS

A study that analyzed the favorable environments of all phonemes of Brazilian Portuguese was sought and, from their data, a pseudoword list for each phoneme, at different levels of favoring, was created. The judging sample of the list was composed of ten judges who reviewed thepseudowords. This analysis was performed in two distinct stages. In the first stage, five judges analyzed the bestpseudowords. In the second stage, the other five judges judged whether pseudowords were essential for therapy. The concordance analysis among the judges was performed through the Content Validity Ratio.

RESULTS

The judges of the first stage reviewed and considerably reduced the number ofpseudowords, from 4000 in total to 1547. And, with the statistical analysis used on the data obtained with the judges of the second stage, the pseudoword list with content validity was reduced to few options. The judges pointed to the simplicity in the structure of pseudowords as a selection criterion.

CONCLUSION

The expert judges' judgment resulted in a small number of pseudowords that have content validity and can be used in phonological therapy.

An Application of Network Science to Phonological Sequence Learning in Children With Developmental Language Disorder

PURPOSE

Network science has been a valuable tool in language research for investigating relationships between complex linguistic elements but has not yet been applied to sound sequencing in production. In the present work, we used standard error-based accuracy and articulatory kinematic approaches as well as novel measures from network science to evaluate variability and sequencing errors in speech production in children with developmental language disorder (DLD; aka specific language impairment).

METHOD

Twelve preschoolers with DLD and 12 age-matched controls participated in a 3-day novel word learning study. Transcription and articulatory movement data were collected to measure accuracy and variability of productions, and networks of speech productions were generated to analyze syllable co-occurrence patterns.

RESULTS

Results indicated that children with DLD were less accurate than children with typical language at the segmental level. Crucially, these findings did not align with performance at the articulatory level, where there were no differences in movement variability between children with DLD and those with typical language. Network analyses revealed characteristics that were not captured by standard measures of phonetic accuracy, including a larger inventory of syllable forms, more connections between the forms, and less consistent production patterns.

CONCLUSIONS

Network science provides significant insights into phonological learning trajectories in children with DLD and their typically developing peers. Importantly, errors in word production by children with DLD do not surface as a result of weakness in articulatory control. Instead, results suggest that speech errors in DLD may relate to deficits in sound sequencing.

Grammatical Word Production Across Metrical Contexts in School-Aged Children's and Adults' Speech

PURPOSE

The purpose of this study is to test whether age-related differences in grammatical word production are due to differences in how children and adults chunk speech for output or to immature articulatory timing control in children.

METHOD

Two groups of 12 children, 5 and 8 years old, and 1 group of 12 adults produced sentences with phrase-medial determiners. Preceding verbs were varied to create different metrical contexts for chunking the determiner with an adjacent content word. Following noun onsets were varied to assess the coherence of determiner-noun sequences. Determiner vowel duration, amplitude, and formant frequencies were measured.

RESULTS

Children produced significantly longer and louder determiners than adults regardless of metrical context. The effect of noun onset on F1 was stronger in children's speech than in adults' speech; the effect of noun onset on F2 was stronger in adults' speech than in children's. Effects of metrical context on anticipatory formant patterns were more evident in children's speech than in adults' speech.

CONCLUSION

The results suggest that both immature articulatory timing control and age-related differences in how chunks are accessed or planned influence grammatical word production in school-aged children's speech. Future work will focus on the development of long-distance coarticulation to reveal the evolution of speech plan structure over time.

The Effect of Transcranial Direct Current Stimulation on Jaw Motor Function Is Task Dependent: Speech, Syllable Repetition and Chewing

Motor cortex transcranial direct current stimulation (tDCS) has been shown to enhance motor learning in healthy adults as well as various neurological conditions. However, there has been limited data on whether tDCS enhances jaw motor performance during different oral behaviors such as speech, maximum syllable repetition, and chewing. Because the effects of anodal and cathodal stimulation are known to be dependent on task demands, we hypothesized that tDCS would have a distinct effect on the jaw motor performance during these disparate oral behaviors. Ten healthy adults completed speech, maximum syllable repetition, and chewing tasks as their jaw movements were recorded using 3D optical motion capture during sham, anodal, and cathodal tDCS. Our findings showed that compared to the sham condition, jaw displacements during speech and syllable repetition were smaller during anodal stimulation, but larger during cathodal stimulation for syllable repetition and chewing indicating improved performance during anodal tDCS. On the other hand, there were no effects of anodal tDCS during chewing. These results confirm our hypotheses that: (1) tDCS induces a significant effect on jaw motor function; (2) its effects are polarity dependent; and (3) its effects are dependent on the task demands on jaw motor function. These findings support future studies exploring the effects of tDCS on persons with oral sensorimotor impairments and the development of therapeutic protocols.

Consonant Age-of-Acquisition Effects in Nonword Repetition Are Not Articulatory in Nature

PURPOSE

Most research examining long-term-memory effects on nonword repetition (NWR) has focused on lexical-level variables. Phoneme-level variables have received little attention, although there are reasons to expect significant sublexical effects in NWR. To further understand the underlying processes of NWR, this study examined effects of sublexical long-term phonological knowledge by testing whether performance differs when the stimuli comprise consonants acquired later versus earlier in speech development.

METHOD

Thirty (Experiment 1) and 20 (Experiment 2) college students completed tasks that investigated whether an experimental phoneme-level variable (consonant age of acquisition) similarly affects NWR and lexical-access tasks designed to vary in articulatory, auditory-perceptual, and phonological short-term-memory demands. The lexical-access tasks were performed in silence or with concurrent articulation to explore whether consonant age-of-acquisition effects arise before or after articulatory planning.

RESULTS

NWR accuracy decreased on items comprising later- versus earlier-acquired phonemes. Similar consonant age-of-acquisition effects were observed in accuracy measures of nonword reading and lexical decision performed in silence or with concurrent articulation.

CONCLUSION

Results indicate that NWR performance is sensitive to phoneme-level phonological knowledge in long-term memory. NWR, accordingly, should not be regarded as a diagnostic tool for pure impairment of phonological short-term memory.

SUPPLEMENTAL MATERIALS

https://doi.org/10.23641/asha.5435137.

Novel phonotactic learning: Tracking syllable-position and co-occurrence constraints

Are syllable-level and co-occurrence representations simultaneously available when one learns novel phonotactics? After training on word-medial consonant restrictions (e.g., word-medial onsets P/Z, codas D/F, and cross-syllable consonant clusters FP/DZ in items like baF.Pev, tiD.Zek), adults falsely recognized novel items containing restricted consonants with the same co-occurrences (e.g., FP) more often than those with different co-occurrences (e.g., FZ) when syllable-position information was kept constant (e.g., vuF.Pet vs. vuF.Zet; Experiment 1). Thus, adults tracked co-occurrence information. Additionally, even when co-occurrence information was different from training, participants more often falsely recognized novel items that contained restricted consonants in the same (e.g., onset-Z) rather than different syllable positions (e.g., coda-Z), whether the restricted consonants were in the same (word-medial, e.g., vuF.Zet vs. vuZ.Fet, Experiment 2) or different word positions (word-edge, e.g., Zut.veF vs. Fut.veZ, Experiment 3). Thus, adults also tracked syllable-level information. These findings show that adults spontaneously represent sound sequences at multiple levels.

Is prosodic production driven by lexical development? Longitudinal evidence from babble and words

This study investigated the relation between lexical development and the production of prosodic prominence in disyllabic babble and words. Monthly recordings from nine typically developing Belgian-Dutch-speaking infants were analyzed from the onset of babbling until a cumulative vocabulary of 200 words was reached. The differentiation between the two syllables of isolated disyllabic utterances was computed for f0, intensity, and duration measurements. Results showed that the ambient trochaic pattern emerged in babble, but became enhanced in words. Words showed more prosodic differentiation in terms of f0 and intensity and a more even duration ratio. Age or vocabulary size did not predict the expansion of f0 or intensity in words, whereas vocabulary size was related to the production of more even-timed syllables. The findings are discussed in terms of lexicalist accounts of phonetic development and a potential phonetic highlighting function of first words.

Perceptual statistical learning over one week in child speech production

What cognitive mechanisms account for the trajectory of speech sound development, in particular, gradually increasing accuracy during childhood? An intriguing potential contributor is statistical learning, a type of learning that has been studied frequently in infant perception but less often in child speech production. To assess the relevance of statistical learning to developing speech accuracy, we carried out a statistical learning experiment with four- and five-year-olds in which statistical learning was examined over one week. Children were familiarized with and tested on word-medial consonant sequences in novel words. There was only modest evidence for statistical learning, primarily in the first few productions of the first session. This initial learning effect nevertheless aligns with previous statistical learning research. Furthermore, the overall learning effect was similar to an estimate of weekly accuracy growth based on normative studies. The results implicate other important factors in speech sound development, particularly learning via production.

The Effect of Word Frequency on Phonemic Accuracy in Children With Cochlear Implants and Peers With Typical Levels of Hearing

The frequency of occurrence of words and sounds has a pervasive influence on typically developing children's language acquisition. For instance, highly frequent words appear earliest in a child's lexicon, and highly frequent phonemes are produced more accurately. This study evaluates (a) whether word frequency influences word accuracy and (b) whether this is also the case for children with a history of auditory deprivation. More specifically, the influence of word frequency on phonemic accuracy is examined in deaf children with a cochlear implant (CI), and compared to age-matched children with typical hearing, between word onset and age 7. Results show that highly frequent words are produced more accurately, except for words in the highest frequency regions (i.e., predominantly closed-class words). This effect is more pronounced in children with typical hearing when compared with children with CI. Thus, children with CI are sensitive to word frequency, but to a lesser extent than peers with typical hearing.

Emergence of a hierarchical brain during infancy reflected by stepwise functional connectivity

The hierarchical nature of the brain's functional organization has long been recognized, but when and how this architecture emerges during development remains largely unknown. Here the development of the brain's hierarchical organization was characterized using a modified stepwise functional connectivity approach based on resting-state fMRI in a fully longitudinal sample of infants (N = 28, with scans after birth, and at 1 and 2 years) and adults. Results obtained by placing seeds in early sensory cortices revealed novel hierarchical patterns of adult brain organization ultimately converging in limbic, paralimbic, basal ganglia, and frontoparietal brain regions. These findings are remarkably consistent with predictive coding accounts of neural processing that place these regions at the top of predictive coding hierarchies. Infants gradually developed toward this architecture in a region- and step-dependent manner, and displayed many of the same regions as adults in top hierarchical positions, starting from 1 year of age. The findings further revealed patterns of inter-sensory connectivity likely reflecting the emergence and development of multisensory processing strategies during infancy, the strengths of which were correlated with early cognitive development scores. Hum Brain Mapp 38:2666-2682, 2017. © 2017 Wiley Periodicals, Inc.

Structural Principles or Frequency of Use? An ERP Experiment on the Learnability of Consonant Clusters

Phonological knowledge of a language involves knowledge about which segments can be combined under what conditions. Languages vary in the quantity and quality of licensed combinations, in particular sequences of consonants, with Polish being a language with a large inventory of such combinations. The present paper reports on a two-session experiment in which Polish-speaking adult participants learned nonce words with final consonant clusters. The aim was to study the role of two factors which potentially play a role in the learning of phonotactic structures: the phonological principle of sonority (ordering sound segments within the syllable according to their inherent loudness) and the (non-) existence as a usage-based phenomenon. EEG responses in two different time windows (adversely to behavioral responses) show linguistic processing by native speakers of Polish to be sensitive to both distinctions, in spite of the fact that Polish is rich in sonority-violating clusters. In particular, a general learning effect in terms of an N400 effect was found which was demonstrated to be different for sonority-obeying clusters than for sonority-violating clusters. Furthermore, significant interactions of formedness and session, and of existence and session, demonstrate that both factors, the sonority principle and the frequency pattern, play a role in the learning process.

Listeners learn phonotactic patterns conditioned on suprasegmental cues

Language learners are sensitive to phonotactic patterns from an early age, and can acquire both simple and 2nd-order positional restrictions contingent on segment identity (e.g., /f/ is an onset with /æ/but a coda with /ɪ/). The present study explored the learning of phonototactic patterns conditioned on a suprasegmental cue: lexical stress. Adults first heard non-words in which trochaic and iambic items had different consonant restrictions. In Experiment 1, participants trained with phonotactic patterns involving natural classes of consonants later falsely recognized novel items that were consistent with the training patterns (legal items), demonstrating that they had learned the stress-conditioned phonotactic patterns. However, this was only true for iambic items. In Experiment 2, participants completed a forced-choice test between novel legal and novel illegal items and were again successful only for the iambic items. Experiment 3 demonstrated learning for trochaic items when they were presented alone. Finally, in Experiment 4, in which the training phase was lengthened, participants successfully learned both sets of phonotactic patterns. These experiments provide evidence that learners consider more global phonological properties in the computation of phonotactic patterns, and that learners can acquire multiple sets of patterns simultaneously, even contradictory ones.

Using Distributional Statistics to Acquire Morphophonological Alternations: Evidence from Production and Perception

Morphophonological alternations, such as the voicing alternation that arises in a morphological paradigm due to final-devoicing in Dutch, are notoriously difficult for children to acquire. This has previously been attributed to their unpredictability. In fact, the presence or absence of a voicing alternation is partly predictable if the phonological context of the word is taken into account, and adults have been shown to use this information (Ernestus and Baayen, 2003). This study investigates whether voicing alternations are predictable from the child’s input, and whether children can make use of this information. A corpus study of child-directed speech establishes that the likelihood of a stem-final obstruent alternating is somewhat predictable on the basis of the phonological properties of the stem. In Experiment 1 Dutch 3-year-olds’ production accuracy in a plural-elicitation task is shown to be sensitive to the distributional statistics. However, distributional properties do not play a role in children’s sensitivity to mispronunciations of voicing in a Preferential Looking Task in Experiment 2.

The influence of phonotactic probability and neighborhood density on children's production of newly learned words

A word learning paradigm was used to teach children novel words that varied in phonotactic probability and neighborhood density. The effects of frequency and density on speech production were examined when phonetic forms were non-referential (i.e., when no referent was attached) and when phonetic forms were referential (i.e., when a referent was attached through fast mapping). Two methods of analysis were included: (1) kinematic variability of speech movement patterning; and (2) measures of segmental accuracy. Results showed that phonotactic frequency influenced the stability of movement patterning whereas neighborhood density influenced phoneme accuracy. Motor learning was observed in both non-referential and referential novel words. Forms with low phonotactic probability and low neighborhood density showed a word learning effect when a referent was assigned during fast mapping. These results elaborate on and specify the nature of interactivity observed across lexical, phonological, and articulatory domains.

Dense neighborhoods and mechanisms of learning: evidence from children with phonological delay

There is a noted advantage of dense neighborhoods in language acquisition, but the learning mechanism that drives the effect is not well understood. Two hypotheses--long-term auditory word priming and phonological working memory--have been advanced in the literature as viable accounts. These were evaluated in two treatment studies enrolling twelve children with phonological delay. Study 1 exposed children to dense neighbors versus non-neighbors before training sound production in evaluation of the priming hypothesis. Study 2 exposed children to the same stimuli after training sound production as a test of the phonological working memory hypothesis. Results showed that neighbors led to greater phonological generalization than non-neighbors, but only when presented prior to training production. There was little generalization and no differential effect of exposure to neighbors or non-neighbors after training production. Priming was thus supported as a possible mechanism of learning behind the dense neighborhood advantage in phonological acquisition.

Stochastic time models of syllable structure

Drawing on phonology research within the generative linguistics tradition, stochastic methods, and notions from complex systems, we develop a modelling paradigm linking phonological structure, expressed in terms of syllables, to speech movement data acquired with 3D electromagnetic articulography and X-ray microbeam methods. The essential variable in the models is syllable structure. When mapped to discrete coordination topologies, syllabic organization imposes systematic patterns of variability on the temporal dynamics of speech articulation. We simulated these dynamics under different syllabic parses and evaluated simulations against experimental data from Arabic and English, two languages claimed to parse similar strings of segments into different syllabic structures. Model simulations replicated several key experimental results, including the fallibility of past phonetic heuristics for syllable structure, and exposed the range of conditions under which such heuristics remain valid. More importantly, the modelling approach consistently diagnosed syllable structure proving resilient to multiple sources of variability in experimental data including measurement variability, speaker variability, and contextual variability. Prospects for extensions of our modelling paradigm to acoustic data are also discussed.

Word recognition and nonword repetition in children with language disorders: the effects of neighborhood density, lexical frequency, and phonotactic probability

PURPOSE

The effects of neighborhood density (ND) and lexical frequency on word recognition and the effects of phonotactic probability (PP) on nonword repetition (NWR) were examined to gain insight into processing at the lexical and sublexical levels in typically developing (TD) children and children with developmental language problems.

METHOD

Tasks measuring NWR and word recognition were administered to 5 groups of children: 2 groups of TD children (5 and 8 years old), children with specific language impairment (SLI), children with reading impairment (RI), and children with SLI+RI (all 7-8 years old).

RESULTS

High ND had a negative effect on word recognition in the older TD children and in the children with RI only. There was no ND effect in the younger children or in the children with SLI, who all had lower receptive vocabulary scores than the age-matched TD children and the RI groups. For all groups, NWR items with low PP were more difficult to repeat than items with high PP. This effect was especially pronounced in children with RI.

CONCLUSION

Both the stage of vocabulary development and the type of language impairment (SLI or RI) impact the way ND and PP affect word recognition and NWR.

Videofluoroscopic investigation of body position on articulatory positioning

PURPOSE

To quantitatively examine the effects of body position on the positioning of the epiglottis, tongue, and velum at rest and during speech.

METHOD

Videofluoroscopic data were obtained from 12 healthy adults in the supine and upright positions at rest and during speech while the participants produced 12 VCV sequences. The effects of body position, target sounds, and adjacent sounds on structural positioning and vowel formant structure were investigated.

RESULTS

Velar retropositioning in the supine position was the most consistent pattern observed at rest. During speech, all structures, with varying degrees of adjustment, appeared to work against the gravitational pull, resulting in no significant narrowing in the oro- and nasopharyngeal regions while in the supine position. Minimal differences in the formant data between the body positions were also observed. Overall, structural positioning was significantly dependent on the target and adjacent sounds regardless of body position.

CONCLUSIONS

The present study demonstrated that structural positioning in response to gravity varied across individuals based on the type of activities being performed. With varying degrees of positional adjustment across different structures, fairly consistent articulatory positioning in the anterior-posterior dimension was maintained in different body positions during speech.

Performance of children on the Turkish Nonword Repetition Test: Effect of word similarity, word length, and scoring

This study aims to report the preliminary results of the development of the Turkish Nonword Repetition Test and to contribute to the clinical accuracy of the test by comparing the performance of children with specific language impairment with that of language-level matched and age-matched typically developing children on a nonword repetition (NWR) test developed for Turkish. To determine the effect of word similarity and word length, the Turkish Nonword Repetition Test is composed of language-like and language-unlike items. To determine the effect of scoring, the performances of children were scored as correct/incorrect for a whole word, for only the consonants, and for only the vowels. The findings suggest that the test is a reliable tool to differentiate Turkish-speaking children with SLI from typically developing children.

Domain-specific and domain-general constraints on word and sequence learning

The relative influences of language-related and memory-related constraints on the learning of novel words and sequences were examined by comparing individual differences in performance of children with and without specific deficits in either language or working memory. Children recalled lists of words in a Hebbian learning protocol in which occasional lists repeated, yielding improved recall over the course of the task on the repeated lists. The task involved presentation of pictures of common nouns followed immediately by equivalent presentations of the spoken names. The same participants also completed a paired-associate learning task involving word-picture and nonword-picture pairs. Hebbian learning was observed for all groups. Domain-general working memory constrained immediate recall, whereas language abilities impacted recall in the auditory modality only. In addition, working memory constrained paired-associate learning generally, whereas language abilities disproportionately impacted novel word learning. Overall, all of the learning tasks were highly correlated with domain-general working memory. The learning of nonwords was additionally related to general intelligence, phonological short-term memory, language abilities, and implicit learning. The results suggest that distinct associations between language- and memory-related mechanisms support learning of familiar and unfamiliar phonological forms and sequences.

Phonological memory in bilinguals and monolinguals

In the present study, we examined the effects of lexical-semantic knowledge and of difficulty level on phonological memory performance by monolingual adult English speakers and bilingual adult Korean-English speakers. The monolingual English speakers were more proficient in English than the bilingual speakers. All participants were tested on a range of phonological memory tasks in English. We manipulated the degree to which the phonological memory tasks involved lexical-semantic knowledge of English (word-span task, digit-span task, and nonword repetition task), as well as the difficulty level of the tasks. Results revealed that on the word-span task (highest level of lexical-semantic knowledge), monolinguals outperformed bilinguals at the easier levels of the task but bilinguals outperformed monolinguals at the more difficult levels of the task. For the digit-span and nonword repetition tasks, monolinguals outperformed bilinguals at the easier levels of the tasks, but the differences between the two groups vanished with the increase in the difficulty levels. Together, these results suggest that proficiency-based differences between monolingual and bilingual phonological memory performance depend on the degree to which the tasks rely on lexical-semantic knowledge and the difficulty level of the task.

Immediate auditory repetition of words and nonwords: an ERP study of lexical and sublexical processing

ERPs were elicited to (1) words, (2) pseudowords derived from these words, and (3) nonwords with no lexical neighbors, in a task involving listening to immediately repeated auditory stimuli. There was a significant early (P200) effect of phonotactic probability in the first auditory presentation, which discriminated words and pseudowords from nonwords; and a significant somewhat later (N400) effect of lexicality, which discriminated words from pseudowords and nonwords. There was no reliable effect of lexicality in the ERPs to the second auditory presentation. We conclude that early sublexical phonological processing differed according to phonotactic probability of the stimuli, and that lexically-based redintegration occurred for words but did not occur for pseudowords or nonwords. Thus, in online word recognition and immediate retrieval, phonological and/or sublexical processing plays a more important role than lexical level redintegration.

A corpus of consonant-vowel-consonant real words and nonwords: comparison of phonotactic probability, neighborhood density, and consonant age of acquisition

A corpus of 5,765 consonant-vowel-consonant sequences (CVCs) was compiled, and phonotactic probability and neighborhood density were computed for both child and adult corpora. This corpus of CVCs, provided as supplementary materials, was analyzed to address the following questions: (1) Do computations based on a child corpus differ from those based on an adult corpus? (2) Do the phonotactic probability and/or the neighborhood density of real words differ from those of nonwords? (3) Do phonotactic probability and/or neighborhood density differ across CVCs that vary in consonant age of acquisition? The results showed significant differences in phonotactic probability and neighborhood density for the child versus adult corpora, replicating prior findings. The impact of this difference on future studies will depend on the level of precision needed when specifying probability and density. In addition, significant and large differences in phonotactic probability and neighborhood density were detected between real words and nonwords, which may present methodological challenges for future research. Finally, CVCs composed of earlier-acquired sounds differed significantly in probability and density from those composed of later-acquired sounds, although this effect was relatively small and is less likely to present significant methodological challenges to future studies.

Nonword repetition and phoneme elision skills in school-age children who do and do not stutter

Nonword repetition and phoneme elision represent the combined influence of several speech and language processes. In the present study we investigated nonword repetition and phoneme elision performance in school-age children who stutter (CWS) and children who do not stutter (CNS). Participants were 14 CWS (mean = 11.7 years, SD = 2.1 years) and age- and sex-matched CNS (mean = 11.8 years, SD = 2.0 years). Each talker group was further subdivided into two age groups: younger (N = 7; 8-11.5 years) and older (N = 7; 11.6-15 years). Repeated-measures analyses were conducted on the accuracy and response time (in seconds) data. In nonword repetition, the CWS showed a trend for lower per cent of correct phonemes at the two-syllable level compared with the CNS. In phoneme elision, the younger CWS showed a significantly lower accuracy rate than the older CWS at the two- and three-syllable nonword lengths, while similar differences were not evident between the younger versus older CNS at any of the nonword lengths. No accuracy difference in phoneme elision was noted between the two talker groups. Group differences in speech initiation times were also not evident in either of the tasks. Findings from nonword repetition offer tentative support for difficulties experienced by school-age CWS in phonemic encoding/working memory abilities. Findings from the phoneme elision task suggest a complex pattern of age-dependent performance by the CWS. Comparison of response accuracy and speech initiation times in both the tasks failed to show speed-accuracy trade-off strategies in either of the groups.

Sequence complexity effects on speech production in healthy speakers and speakers with hypokinetic or ataxic dysarthria

The present study investigated the effects of sequence complexity, defined in terms of phonemic similarity and phonotoactic probability, on the timing and accuracy of serial ordering for speech production in healthy speakers and speakers with either hypokinetic or ataxic dysarthria. Sequences were comprised of strings of consonant-vowel (CV) syllables with each syllable containing the same vowel, /a/, paired with a different consonant. High complexity sequences contained phonemically similar consonants, and sounds and syllables that had low phonotactic probabilities; low complexity sequences contained phonemically dissimilar consonants and high probability sounds and syllables. Sequence complexity effects were evaluated by analyzing speech error rates and within-syllable vowel and pause durations. This analysis revealed that speech error rates were significantly higher and speech duration measures were significantly longer during production of high complexity sequences than during production of low complexity sequences. Although speakers with dysarthria produced longer overall speech durations than healthy speakers, the effects of sequence complexity on error rates and speech durations were comparable across all groups. These findings indicate that the duration and accuracy of processes for selecting items in a speech sequence is influenced by their phonemic similarity and/or phonotactic probability. Moreover, this robust complexity effect is present even in speakers with damage to subcortical circuits involved in serial control for speech.

Developmental change is key to understanding primary language impairment: the case of phonotactic probability and nonword repetition

PURPOSE

In this study, the authors aimed to explore the relationship between lexical and phonological knowledge in children with primary language impairment (PLI) through the application of a developmental methodology. Specifically, they tested whether there is evidence for an impairment in the process of phonological abstraction in this group of children over and above that which would be predicted by their vocabulary growth.

METHOD

The authors measured developmental change in the abilities of typically developing (TD) children ( n = 38, chronological age [CA] = 3;0-5;6 [years;months]) and those with PLI ( n = 13, CA = 3;0-6;6 and 4;6-8;0) to repeat nonwords with high and low phonotactic probability (PP) to uncover group differences in the process of abstraction of phonological representations.

RESULTS

Cross-sectional developmental trajectories of change in nonword repetition abilities were compared across CA and vocabulary growth. Unlike TD children, the children with PLI did not evince a narrowing gap in the influence of PP across development, and they reached a plateau in their development.

CONCLUSION

These results suggest slowed emergence of phonological representations in PLI, with a plateau in the development of lexical-phonological representations. This plateau may represent entrenchment and "fixing" due to a missed critical period and/or atypical word learning biases in PLI.

Wordlikeness and word learning in children with hearing loss

BACKGROUND

The more a novel word conforms to the phonotactics of the language, the more wordlike it is and the easier it is to learn. It is unknown to what extent children with hearing loss (CHL) take advantage of phonotactic cues to support word learning.

AIMS

This study investigated whether CHL had similar sensitivities to wordlikeness during a word-learning task as children with normal hearing (CNH).

METHODS & PROCEDURES

Sixteen CHL and 24 CNH participated in a novel word-learning task. Novel words varied by English wordlikeness. Recall was tested using a forced-choice identification task wherein foils for each trial related semantically, lexically or not at all. Receptive vocabulary and working memory were also assessed.

OUTCOMES & RESULTS

All children were able to identify high wordlike novel words more accurately than low wordlike novel words. The number of errors on identification of words that were moderate in wordlikeness was inversely correlated to vocabulary size (not working memory) and CHL had smaller vocabularies than CNH. When in error, CHL were more likely than CNH to select a semantically related foil.

CONCLUSIONS & IMPLICATIONS

Although they are sensitive to extremes in wordlikeness, compared with their peers with normal hearing, CHL present with subtle differences in word learning. Clinical implications for exploiting wordlikeness in service of word learning assessment and intervention are presented.

Density, frequency and the expressive phonology of children with phonological delay

The effect of word-level variables on expressive phonology has not been widely studied, although the properties of words likely bear on the emergence of sound structure (Stoel-Gammon, 2011). Eight preschoolers, diagnosed with phonological delay, were assigned to treatment to experimentally induce gains in expressive phonology. Erred sounds were taught using stimulus words that varied orthogonally in neighborhood density and word frequency as the independent variables. Generalization was the dependent variable, defined as production accuracy of treated and untreated (erred) sounds. Blocked comparisons showed that dense neighborhoods triggered greater generalization, but frequency did not have a clear differential effect. Orthogonal comparisons revealed graded effects, with frequent words from dense neighborhoods being optimal for generalization. The results contrast with prior literature, which has reported a sparse neighborhood advantage for children with phonological delay. There is a suggestion that children with phonological delay require greater than usual cue redundancy and convergence to prompt expressive phonological learning.

Nonword repetition: the relative contributions of phonological short-term memory and phonological representations in children with language and reading impairment

PURPOSE

This study investigates the relative contributions of phonological short-term memory and phonological representations to nonword repetition (NWR). This was evaluated in children with specific language impairment (SLI) and/or reading impairment (RI); it was also studied from a developmental perspective by comparing 2 groups of typically developing (TD) children who differed in age.

METHOD

NWR, digit span, vocabulary, and word and nonword discrimination were tested in 2 groups of TD children: one group matched on chronological age (CA TD group: n = 41, mean age = 7;8 [months;years]), and one language age-matched control group (LA TD group: n = 16, mean age = 5;8). Also, 10 children with SLI, 14 children with RI, and 23 children with SLI and RI (hereafter, SLI + RI) participated and were matched to the age of the CA TD group.

RESULTS

For the TD children, NWR was predicted by discrimination, digit span, and age. The interaction between discrimination ability and age was also significant. Children with SLI + RI were significantly impaired on NWR compared with all other groups. A regression analysis, including the CA TD group and the children with SLI and/or RI, showed that digit span, discrimination ability, and group (SLI + RI) contributed significantly to NWR.

CONCLUSIONS

Phonological short-term memory and phonological representations both significantly contribute to NWR. The predictive strength of the quality of phonological representations changes during development.

Lexical and phonological effects in early word production

PURPOSE

This study examines the influence of word frequency, phonological neighborhood density (PND), age of acquisition (AoA), and phonotactic probability on production variability and accuracy of known words by toddlers with no history of speech, hearing, or language disorders.

METHOD

Fifteen toddlers between 2;0 (years;months) and 2;5 produced monosyllabic target words varying in word frequency, PND, AoA, and phonotactic probability. Phonetic transcription was used to determine (a) whole-word variability and (b) proportion of whole-word proximity (PWP; Ingram, 2002) of each target word produced.

RESULTS

Results show a significant effect of PND on PWP and variability (words from dense neighborhoods had higher PWP and lower variability than those from sparse neighborhoods), a significant effect of word frequency on variability (high-frequency words were less variable) but not proximity, and a significant effect of AoA on proximity (earlier acquired words had lower PWP) but not variability.

CONCLUSIONS

Results provide new information regarding the role that lexical and phonological factors play in the speech of young children; specifically, several factors are identified that influence variability of production. Additionally, by examining lexical and phonological factors simultaneously, the current study isolates differential effects of the individual factors. Implications for our understanding of emerging phonological representations are discussed.

Contributions of phonetic token variability and word-type frequency to phonological representations

The experiments here build on the widely reported finding that children are most accurate when producing phonotactic sequences with high ambient-language frequency. What remains controversial is a description of the input that children must be tracking for this effect to arise. We present a series of experiments that compare two ambient-language properties, token and type frequency, as they contribute to phonotactic learning. Token frequency is the raw number of exposures children have to a particular pattern; type frequency refers to a count of abstract entities, such as unique words. Our results suggest that children's production accuracy is most sensitive to a combination of type and token frequency: children were able to generalize a target phonotactic sequence to a new word when familiarized with multiple word-types across tokens from multiple talkers, but not when presented with either word-types with no talker variability or multiple talker-tokens of a single word.