Jan Edwards

Nonword repetitions of children with specific language impairment: Exploration of some explanations for their inaccuracies

To examine possible explanations of the reported inaccuracies of children with specific language impairment (SLI) on nonword repetition, we compared the repetitions of 54 children with SLI and their peers in terms of number and type of error as well as latency and duration of response. We found no evidence of differences between the groups in auditory discrimination or response processes, but we did find some evidence suggesting differences in either the formation or storage of phonological representations in working memory. Because repetition accuracy was significantly correlated with expressive, but not receptive, measures of language, we hypothesized that the problem lay with the nature of phonological representations in working memory and not with the ability to hold phonological information in working memory.

The articulatory kinematics of final lengthening

In order to understand better the phonetic control of final lengthening, the articulation of phrase-final syllables was compared with that of two other contexts known to increase syllable duration: accent and slow tempo. The kinematics of jaw movements in [pap] sequences and of lower lip movements in [pe] sequences for four subjects were interpreted in terms of a task-dynamic model. There was evidence of two different control strategies: decreasing intragestural stiffness to slow down some part of the syllable, and changing intergestural phasing to decrease overlap of the vowel gesture by the consonant. The first was used in slowing down tempo, whereas the second was used to increase the duration of accented syllables over unaccented syllables. Both strategies were implicated in phrase-final lengthening. In accented syllables, final closing gestures generally were longer and slower, but not more displaced. The two slowest subjects, however, used the other strategy in their slow-tempo final syllables. Final lengthening in reduced syllables was more difficult to interpret. The relationship between peak velocity and displacement suggested that a lesser stiffness is obscured by an increased gestural amplitude. Thus, by comparison to lengthening for accent, final lengthening is like a localized change in speaking tempo, although it cannot be equated directly with the specification of stiffness.

Contrast and covert contrast: The phonetic development of voiceless sibilant fricatives in English and Japanese toddlers

This paper examines the acoustic characteristics of voiceless sibilant fricatives in English-and Japanese-speaking adults and the acquisition of contrasts involving these sounds in 2- and 3-year-old children. Both English and Japanese have a two-way contrast between an alveolar fricative (/s/), and a postalveolar fricative (/∫/ in English and /ɕ/ in Japanese). Acoustic analysis of the adult productions revealed cross-linguistic differences in what acoustic parameters were used to differentiate the two fricatives in the two languages and in how well the two fricatives were differentiated by the acoustic parameters that were investigated. For the childrens data, the transcription results showed that English-speaking children generally produced the alveolar fricative more accurately than the postalveolar one, whereas the opposite was true for Japanese-speaking children. In addition, acoustic analysis revealed the presence of covert contrast in the productions of some English-speaking and some Japanese-speaking children. The different development patterns are discussed in terms of the differences in the fine phonetic detail of the contrast in the two languages.

The interplay between prosodic structure and coarticulation

In this paper we draw on a linguistic model of prosodic structure and a task-dynamic model of speech gestures to account for the interplay of coarticulation and stress in English. We reinterpret results from two experiments in which articulator movements were recorded for utterances varying in pitch accent placement. In the first experiment, jaw kinematics were studied in post-nuclear unaccented and nuclear accented [pap] syllables. The kinematic patterns suggested that gestures in syllables with greater stress (nuclear accented) show less coarticulatory overlap. By contrast, the vowels low jaw target is undershot in unaccented syllables. Two hypotheses are possible. Either the jaw is lower in stressed syllables so more energy can radiate from the mouth (“sonority expansion”) or the jaw is lower to help distinguish the low vowel from other vowels (“hyperarticulation”). Another experiment differentiates the two hypotheses by examining tongue point positions in [put] preceding a [Ö]. In the more stressed syllables, the tongue dorsum retracts more, likely to make a more distinct back vowel. Also, the amount of assimilation of the alveolar stop to the following dental is reduced. Both results suggest hyperarticulation rather than sonority expansion. Thus, it seems that coarticulation is reduced in stressed syllables, because stressed syllables are hyperarticulated.

The Ontogeny of Phonological Categories and the Primacy of Lexical Learning in Linguistic Development.

In this paper, we draw on recent developments in several areas of cognitive science that suggest that the lexicon is at the core of grammatical generalizations at several different levels of representation. Evidence comes from many sources, including recent studies on language processing in adults and on language acquisition in children. Phonological behavior is influenced very early by pattern frequency in the lexicon of the ambient language, and we propose that phonological acquisition might provide the initial bootstrapping into grammatical generalization in general. The phonological categories over which pattern frequencies are calculated, however, are neither transparently available in the audiovisual signal nor deterministically fixed by the physiological and perceptual capacities of the species. Therefore, we need several age-appropriate models of how the lexicon can influence a childs interactions with the ambient language over the course of phonological acquisition.

Articulatory Timing and the Prosodic Interpretation of Syllable Duration

A number of different prosodic effects (e. g. intonation-phrase-final position, the presence of stress or accent) increase syllable duration, as conventionally measured by the spacing of abrupt energy transitions in the acoustic signal. However, different prosodic contrasts may have different influences on syllable-internal articulatory organization. The present study examined the time course of vowel-related opening and closing mandibular gestures in four different prosodic contexts. For some prosodic effects, such as intonation-phrase-final lengthening, longer acoustic durations were associated with a disproportionate lengthening of the latter part of the vocalic gesture. By contrast, the presence of nuclear stress was associated with a more even distribution of lengthening throughout the syllable. These results suggest that the rhythmic effects of different prosodic contrasts cannot be adequately modelled in terms of millisecond values or durational ratios for acoustic segments. It is proposed that a suitable phonological representation of the rhythms of stress and phrasing might describe them as the time course of a syllable’s phonetic sonority.

Some Cross-Linguistic Evidence for Modulation of Implicational Universals by Language-Specific Frequency Effects in Phonological Development

Although broad-focus comparisons of consonant inventories across children acquiring different languages can suggest that phonological development follows a universal sequence, finer-grained statistical comparisons can reveal systematic differences. This cross-linguistic study of word-initial lingual obstruents examined some effects of language-specific frequencies on consonant mastery. Repetitions of real words were elicited from 2- and 3-year-old children who were monolingual speakers of English, Cantonese, Greek, or Japanese. The repetitions were recorded and transcribed by an adult native speaker for each language. Results found support for both language-universal effects in phonological acquisition and for language-specific influences related to phoneme and phoneme sequence frequency. These results suggest that acquisition patterns that are common across languages arise in two ways. One influence is direct, via the universal constraints imposed by the physiology and physics of speech production and perception, and how these predict which contrasts will be easy and which will be difficult for the child to learn to control. The other influence is indirect, via the way universal principles of ease of perception and production tend to influence the lexicons of many languages through commonly attested sound changes.

Methodological questions in studying consonant acquisition

Consonant mastery is one of the most widely used metrics of typical phonological acquisition and of phonological disorder. Two fundamental methodological questions concerning research on consonant acquisition are (1) how to elicit a representative sample of productions and (2) how to analyse this sample once it has been collected. This paper address these two questions by reviewing relevant aspects of experience in evaluating word‐initial consonant accuracy from transcriptions of isolated‐word productions elicited from 2‐ and 3‐year‐olds learning four different first languages representing a telling range of consonant systems (English, Cantonese, Greek, Japanese). It is suggested that both researchers and clinicians should consider a number of different item‐related factors, such as phonotactic probability and word length, when constructing word lists to elicit consonant productions from young children. This study also proposes that transcription should be supplemented by acoustic analysis and the perceptual judgements of naïve listeners.

Phonological Knowledge in Typical and Atypical Speech–sound Development

This article discusses 4 types of phonological knowledge: knowledge of the acoustic and perceptual characteristics of speech sounds (perceptual knowledge), knowledge of the articulatory characteristics of speech sounds (articulatory knowledge), higher level knowledge of the ways that words can be divided into sounds and related phonotactic constraints on how sounds can be combined into words (higher level phonological knowledge), and knowledge of the ways that variation in pronunciation can be used to convey social identity (social–indexical knowledge). The first section of the article discusses the nature of these types of knowledge in adults. The second describes how they develop in children with typical language development. The third section outlines how different types of knowledge may be compromised in children with functional speech–sound impairments. Together, these 3 sections serve as a review for practicing clinicians of the types of phonological knowledge that underlie accurate and fluent speech production.

The Impact of Auditory Spectral Resolution on Listening Effort Revealed by Pupil Dilation

Objectives: This study measured the impact of auditory spectral resolution on listening effort. Systematic degradation in spectral resolution was hypothesized to elicit corresponding systematic increases in pupil dilation, consistent with the notion of pupil dilation as a marker of cognitive load. Design: Spectral resolution of sentences was varied with two different vocoders: (1) a noise-channel vocoder with a variable number of spectral channels; and (2) a vocoder designed to simulate front-end processing of a cochlear implant, including peak-picking channel selection with variable synthesis filter slopes to simulate spread of neural excitation. Pupil dilation was measured after subject-specific luminance adjustment and trial-specific baseline measures. Mixed-effects growth curve analysis was used to model pupillary responses over time. Results: For both types of vocoder, pupil dilation grew with each successive degradation in spectral resolution. Within each condition, pupillary responses were not related to intelligibility scores, and the effect of spectral resolution on pupil dilation persisted even when only analyzing trials in which responses were 100% correct. Conclusions: Intelligibility scores alone were not sufficient to quantify the effort required to understand speech with poor resolution. Degraded spectral resolution results in increased effort required to understand speech, even when intelligibility is at 100%. Pupillary responses were a sensitive and highly granular measurement to reveal changes in listening effort. Pupillary responses might potentially reveal the benefits of aural prostheses that are not captured by speech intelligibility performance alone as well as the disadvantages that are overcome by increased listening effort.