Variation in the speech signal as a window into the cognitive architecture of language production

Testing for canonical form orientation in speech tempo perception

We report on two experiments that aimed to test the hypothesis that English listeners orient to full pronunciation forms-"canonical forms"-in judging the tempo of speech that features deletions. If listeners orient to canonical forms, this should mean that the perceived tempo of speech containing deletions is highly relative to the speech's articulation rate calculated on the basis of surface phone strings. We used controlled stimuli to test this hypothesis. We created sentences with one ambiguous word form (for example, support~sport), to give half of the listeners an orthographic form that includes support and the other half an otherwise identical orthographic form with sport. In both experiments, listeners judged the tempo of the sentences, which allowed us to assess whether the difference in imposed interpretation had an impact on perceived tempo. Experiment 1 used a tempo rating task in which listeners evaluated the tempo of experimental stimuli relative to comparison stimuli, on a continuous scale. Experiment 2 used a tempo comparison task in which listeners judged whether second members of stimulus pairs were slower or faster than first members. Both experiments revealed the predicted effect of the imposed word interpretation: sentences with an imposed "schwa" interpretation for the ambiguous word form were judged faster than (the same) sentences with an imposed "no schwa" interpretation. However, in both experiments the effect was small and variables related to the experimental design had significant effects on responses. We discuss the results' implications for our understanding of speech tempo perception.

Diagnosing inconsistent phonological disorder: quantitative and qualitative measures

Studies of children's consistency of word production allow identification of speech sound disorder. Inconsistent errors are reported for two groups of children: childhood apraxia of speech (CAS) due to difficulty with the motoric precision and consistency of speech movements; and inconsistent phonological disorder (IPD) attributed to impaired phonological planning. This paper describes the inconsistent productions of children with IPD in comparison to typically developing children. In two studies of suspected SSD (N = 135), 22 children pronounced ≥40% of 25 words inconsistently on three repeated trials. No participant had symptoms of CAS. They were monolingual and spoke Australian- or Irish-English. Assessment determined the proportions of words said consistently (i.e. the same across productions: all correct or with the same error) or inconsistently (i.e. differently across productions: at least one correct and one error or different errors in productions). Qualitative analyses examined error types and explored the effect of target words' characteristics on inconsistency. Children with IPD produced 52% of words with different errors. While 56% of all phoneme errors were developmental (age appropriate or delayed), atypical errors typified inconsistency: default sounds and word structure errors. Words with more phonemes, syllables and consonant clusters were vulnerable to inconsistency, but their frequency of occurrence had no effect. TD children and those with IPD had different quantitative and qualitative error profiles, confirming IPD as a diagnostic category of SSD. Qualitative analyses supported the hypothesised deficit in phonological planning of words' production for children with IPD.

Talkitt: toward a new instrument based on artificial intelligence for augmentative and alternative communication in children with down syndrome

Introduction

Individuals with Down syndrome (DS) often exhibit a severe speech impairment, with important consequences on language intelligibility. For these cases, the use of Augmentative Alternative Communication instruments, that increase an individual's communication abilities, becomes crucial. Talkitt is a mobile application created by Voiceitt Company, exploiting speech recognition technology and artificial intelligence models to translate in real-time unintelligible sounds into clear words, allowing individuals with language production impairment to verbally communicate in real-time.

Methods

The study evaluated the usability and satisfaction related to the Talkitt application use, as well as effects on adapted behavior and communication, of participants with DS. A final number of 23 individuals with DS, aged 5.54 to 28.9 years, participated in this study and completed 6 months of training. The application was trained to consistently recognize at least 20 different unintelligible words (e.g., nouns and/or short phrases)/person.

Results

Results revealed good usability and high levels of satisfaction related to the application use. Moreover, we registered improvement in linguistic abilities, particularly naming.

Discussion

These results paves the road for a potential role of Talkitt application as a supportive and rehabilitative tool for DS.

Preschool children's consistency of word production

Consistency of word production contributes to carers' ability to understand children's speech. Reports of the proportion of words produced consistently by typically developing preschool children, however, vary widely from 17% to 87%. This paper examines the quantitative (consistency count) and qualitative (e.g. phonemic analysis) characteristics of word consistency in 96 children aged 36-60 months. Children named 15 pictures twice, in separate trials, in the same assessment session. The mean consistency of the production for the whole group was 82%. Older children were more consistent than younger children. Girls were more consistent than boys. Words produced correctly in one trial and in error in another may indicate resolving error patterns. Words produced in error in two different ways provided useful evidence about the nature of inconsistent word production in typically developing children. The clinical and theoretical implications are discussed.

Exploring Variability in Compound Tensification in Seoul Korean

In Korean noun-noun compounds, the lenis onset consonant in the second noun is often realized as a tense consonant. Although extensive work has been carried out to clarify its causes and relevant phonological processes, this tensification is deemed not entirely predictable. This paper presents a speech production experiment that confirms the existing findings that the variability in tensification is predictable to a certain extent. The experimental results also showed that the relationship between the predictors and the variability is not linear and that tensification mirrors the cognitively determined boundary strength. Native Korean speakers calibrate the boundary strength by incorporating complex information, such as the word's length, segment type, frequency, and plausibility of the compound. While a "tight" boundary led to high tensification probability, it was not affected by speaking-rate variation. Furthermore, the perceived compound's plausibility directly affected the duration of the tensified consonant. Importantly, the findings suggest that speakers' calibration of the boundary strength is fluid and changeable over time and it affects both phonological and phonetic outputs. Finally, variability in data was reduced for the experimental conditions leading to either extremely high or low tensification probability, and there seemed to be lexicalized exceptions to the general trends.

Encoding category-level and context-specific phonological information at different stages: An EEG study of Mandarin third-tone sandhi word production

Pronunciation of words or morphemes may vary systematically in different phonological contexts, but it remains unclear how different levels of phonological information are encoded in speech production. In this study, we investigated the online planning process of Mandarin Tone 3 (T3) sandhi, a case of phonological alternation whereby a low-dipping tone (T3) changes to a Tone 2 (T2)-like rising tone when followed by another T3. To examine the time course of the encoding of the abstract category-level (underlying form) and context-specific phonological form (surface form) of T3, we conducted an electroencephalographic (EEG) study with a phonologically-primed picture naming task and examined the event-related potentials (ERPs) time-locked to the stimulus onset as well as speech response onset. The behavioral results showed that targets primed by T3 or T2 primes yielded shorter naming latencies than those primed by control primes. Importantly, the EEG data revealed that T3 primes elicited larger positive amplitude over broad frontocentral regions roughly in the 320-550 ms time window of stimulus-locked ERP and -500 to -400 ms time window of response-locked ERP, whereas T2 primes elicited larger negative amplitude over left frontocentral regions roughly in the -240 to -100 ms time window of response-locked ERP. These results indicate that the underlying and the surface form are encoded at different processing stages. The former presumably occurs in the earlier phonological encoding stage, while the latter probably occurs in the later phonetic encoding or motor preparation stage. The current study offers important implications for understanding the processing of phonological alternations and tonal encoding in Chinese word production.

Towards a model of language neurobiology in early development

Understanding language neurobiology in early childhood is essential for characterizing the developmental structural and functional changes that lead to the mature adult language network. In the last two decades, the field of language neurodevelopment has received increasing attention, particularly given the rapid advances in the implementation of neuroimaging techniques and analytic approaches that allow detailed investigations into the developing brain across a variety of cognitive domains. These methodological and analytical advances hold the promise of developing early markers of language outcomes that allow diagnosis and clinical interventions at the earliest stages of development. Here, we argue that findings in language neurobiology need to be integrated within an approach that captures the dynamic nature and inherent variability that characterizes the developing brain and the interplay between behavior and (structural and functional) neural patterns. Accordingly, we describe a framework for understanding language neurobiology in early development, which minimally requires an explicit characterization of the following core domains: i) computations underlying language learning mechanisms, ii) developmental patterns of change across neural and behavioral measures, iii) environmental variables that reinforce language learning (e.g., the social context), and iv) brain maturational constraints for optimal neural plasticity, which determine the infant's sensitivity to learning from the environment. We discuss each of these domains in the context of recent behavioral and neuroimaging findings and consider the need for quantitatively modeling two main sources of variation: individual differences or trait-like patterns of variation and within-subject differences or state-like patterns of variation. The goal is to enable models that allow prediction of language outcomes from neural measures that take into account these two types of variation. Finally, we examine how future methodological approaches would benefit from the inclusion of more ecologically valid paradigms that complement and allow generalization of traditional controlled laboratory methods.

Acoustic and speaker variation in Dutch /n/ and /m/ as a function of phonetic context and syllabic position

In forensic speech science, nasals are often reported to be particularly useful in characterizing speakers because of their low within-speaker and high between-speaker variability. However, empirical acoustic data from nasal consonants indicate that there is a somewhat larger role for the oral cavity in nasal consonant acoustics than is generally predicted by acoustic models. For example, in read speech, nasal consonant acoustics show lingual coarticulation that differs by nasal consonant, and syllabic position also seems to affect realizations of nasal consonants within speakers. In the current exploratory study, the within- and between-speaker variation in the most frequent nasals in Standard Dutch, /n/ and /m/, was investigated. Using 3695 [n] and 3291 [m] tokens sampled from 54 speakers' spontaneous telephone utterances, linear mixed-effects modeling of acoustic-phonetic features showed effects of phonetic context that differed by nasal consonant and by syllabic position. A subsequent speaker-classification test using multinomial logistic regression on the acoustic-phonetic features seems to indicate that nasals displaying larger effects of phonetic context also perform slightly better in speaker classification, although differences were minor. This might be caused by between-speaker variation in the degree and timing of lingual coarticulatory gestures.