Lisa Goffman

Spatiotemporal stability and patterning of speech movement sequences

In order to examine the stability and patterning of speech movement sequences, movements of the lip were recorded as subjects produced a phrase at normal, fast, and slow rates. Three methods of analysis were employed. First, a new index of spatiotemporal stability was derived by summing the standard deviations computed across amplitude- and time-normalized displacement records. This index indicated that normal and fast rates of speech production result in more stable movement execution compared to slow rates. In the second analysis, the relative time of occurrence of the peak velocity of the three middle opening movements of the utterance was measured. For each of the three peaks, the preservation of relative timing was assessed by applying Genters (1987) slope test. The results clearly indicate that the relative timing of these events does not remain constant across changes in speech rate. The relative timing of the middle opening gestures shifted, becoming later as utterance duration increased. In a third analysis, pattern recognition techniques were applied to the normalized displacement waveforms. A classification algorithm was highly successful in sorting waveforms into normal, fast, and slow rate conditions. These findings were interpreted to suggest that, within a subject, three distinct patterns or movement templates exist, one for each rate of production. Speech rate appears to be a global parameter, one that affects the entire command sequence for the utterance.

Development and phonetic differentiation of speech movement patterns.

It is often hypothesized that speech production units are less distinctive in young children and that generalized movement primitives, or templates, serve as a base on which distinctive, mature templates are later elaborated. This hypothesis was examined by analyzing the shape and stability of single close-open speech movements of the lower lip recorded in 4-year-old, 7-year-old, and adult speakers during production of utterances that varied in only a single phoneme. To assess the presence of a generalized template, lower lip movement sequences were time and amplitude normalized, and a pattern recognition procedure was implemented. The findings indicate that speech movements of children already converged on phonetically distinctive patterns by 4 years of age. In contrast, an index of spatiotemporal stability demonstrated that the stability of underlying patterning of the movement sequence improves with maturation.

Growth of Language Skills in Preschool Children With Specific Language ImpairmentImplications for Assessment and Intervention

A retrospective longitudinal study of 9 preschool-aged children, all meeting the criteria for specific language impairment (SLI), was conducted. Language growth was documented while the children we...

Statistical frequency in perception affects children’s lexical production

Childrens early word production is influenced by the statistical frequency of speech sounds and combinations. Three experiments asked whether this production effect can be explained by a perceptual learning mechanism that is sensitive to word-token frequency and/or variability. Four-year-olds were exposed to nonwords that were either frequent (presented 10 times) or infrequent (presented once). When the frequent nonwords were spoken by the same talker, children showed no significant effect of perceptual frequency on production. When the frequent nonwords were spoken by different talkers, children produced them with fewer errors and shorter latencies. The results implicate token variability in perceptual learning.

Language and motor abilities of preschool children who stutter: Evidence from behavioral and kinematic indices of nonword repetition performance

UNLABELLED Stuttering is a disorder of speech production that typically arises in the preschool years, and many accounts of its onset and development implicate language and motor processes as critical underlying factors. There have, however, been very few studies of speech motor control processes in preschool children who stutter. Hearing novel nonwords and reproducing them engages multiple neural networks, including those involved in phonological analysis and storage and speech motor programming and execution. We used this task to explore speech motor and language abilities of 31 children aged 4-5 years who were diagnosed as stuttering. We also used sensitive and specific standardized tests of speech and language abilities to determine which of the children who stutter had concomitant language and/or phonological disorders. Approximately half of our sample of stuttering children had language and/or phonological disorders. As previous investigations would suggest, the stuttering children with concomitant language or speech sound disorders produced significantly more errors on the nonword repetition task compared to typically developing children. In contrast, the children who were diagnosed as stuttering, but who had normal speech sound and language abilities, performed the nonword repetition task with equal accuracy compared to their normally fluent peers. Analyses of interarticulator motions during accurate and fluent productions of the nonwords revealed that the children who stutter (without concomitant disorders) showed higher variability in oral motor coordination indices. These results provide new evidence that preschool children diagnosed as stuttering lag their typically developing peers in maturation of speech motor control processes. EDUCATIONAL OBJECTIVES The reader will be able to: (a) discuss why performance on nonword repetition tasks has been investigated in children who stutter; (b) discuss why children who stutter in the current study had a higher incidence of concomitant language deficits compared to several other studies; (c) describe how performance differed on a nonword repetition test between children who stutter who do and do not have concomitant speech or language deficits; (d) make a general statement about speech motor control for nonword production in children who stutter compared to controls.

Lexical and articulatory interactions in children’s language production

Traditional models of adult language processing and production include two levels of representation: lexical and sublexical. The current study examines the influence of the inclusion of a lexical representation (i.e. a visual referent and/or object function) on the stability of articulation as well as on phonetic accuracy and variability in typically developing children and children with specific language impairment (SLI). A word learning paradigm was developed so that we could compare childrens production with and without lexical representation. The variability and accuracy of productions were examined using speech kinematics as well as traditional phonetic accuracy measures. Results showed that phonetic forms with lexical representation were produced with more articulatory stability than phonetic forms without lexical representation. Using more traditional transcription measures, a paired lexical referent generally did not influence segmental accuracy (percent consonant correct and type token ratio). These results suggest that lexical and articulatory levels of representation are not completely independent. Implications for models of language production are discussed.

Mapping of prosodic structure onto words and phrases in children's and adults' speech production

Direct recordings of lip and jaw movement were obtained to investigate how children and adults differentiate prosodic structure both within iambic and trochaic words and across word boundaries. It was hypothesised that children, especially those with less language skills, would be particularly likely to produce strong-weak (or trochaic) sequences. This experiment examined childrens (both normally developing and specifically language impaired, aged 4–6 years) and adults’ productions of prosodic sequences that were controlled for syntactic and phonetic content, but that differed in rhythmic alternations, both within words (i. e., iambs vs. trochees) and across words (i. e., optimal strong-weak vs. stress gap or stress clash). To avoid final position effects, target words were in utterance internal position. Analyses included kinematic measures of prosodic structure (i. e., amplitude and duration of movements in weak vs. strong syllables; ratios of weak-to-strong movements). Consistent with prior work, weak syllables in iambs were produced differentially from those in trochees; though these effects were now observed in utterance position. However, in noun-noun sequences within a phrase, even when the rhythm rule was violated, prosodic foot structure was not reorganised as a function of rhythmic properties of the utterance. Overall, children with the least mature language skills demonstrated poor control of temporal and amplitude aspects of movement, especially in weak syllables. Findings are related to the organisation of speech production units across prosodic levels.

The Influence of Prosodic Stress Patterns and Semantic Depth on Novel Word Learning in Typically Developing Children

The goal of this study was to investigate the effects of prosodic stress patterns and semantic depth on word learning. Twelve preschool-aged children with typically developing speech and language skills participated in a word learning task. Novel words with either a trochaic or iambic prosodic pattern were embedded in one of two learning conditions, either in childrens stories (semantically rich) or picture matching games (semantically sparse). Three main analyses were used to measure word learning: comprehension and production probes, phonetic accuracy, and speech motor stability. Results revealed that prosodic frequency and density influence the learnability of novel words, and that there are prosodic neighborhood density effects. The impact of semantic depth on word learning was minimal and likely depends on the amount of experience with the novel words.

Reading skill and exposure to orthography influence speech production

Orthographic experience during the acquisition of novel words may influence production processing in proficient readers. Previous work indicates interactivity among lexical, phonological, and articulatory processing; we hypothesized that experience with orthography can also influence phonological processing. Phonetic accuracy and articulatory stability were measured as adult, proficient readers repeated and read aloud nonwords, presented in auditory or written modalities and with variations in orthographic neighborhood density. Accuracy increased when participants had read the nonwords earlier in the session, but not when they had only heard them. Articulatory stability increased with practice, regardless of whether nonwords were read or heard. Word attack skills, but not reading comprehension, predicted articulatory stability. Findings indicate that kinematic and phonetic accuracy analyses provide insight into how orthography influences implicit language processing.

Deficits in Coordinative Bimanual Timing Precision in Children with Specific Language Impairment.

Purpose Our objective was to delineate components of motor performance in specific language impairment (SLI); specifically, whether deficits in timing precision in one effector (unimanual tapping) and in two effectors (bimanual clapping) are observed in young children with SLI. Method Twenty-seven 4- to 5-year-old children with SLI and 21 age-matched peers with typical language development participated. All children engaged in a unimanual tapping and a bimanual clapping timing task. Standard measures of language and motor performance were also obtained. Results No group differences in timing variability were observed in the unimanual tapping task. However, compared with typically developing peers, children with SLI were more variable in their timing precision in the bimanual clapping task. Nine of the children with SLI performed greater than 1 SD below the mean on a standardized motor assessment. The children with low motor performance showed the same profile as observed across all children with SLI, with unaffected unimanual and impaired bimanual timing precision. Conclusions Although unimanual timing is unaffected, children with SLI show a deficit in timing that requires bimanual coordination. We propose that the timing deficits observed in children with SLI are associated with the increased demands inherent in bimanual performance.