Michele L. Morrisette

Phonological Treatment Efficacy and Developmental Norms

The efficacy of teaching sounds in developmental sequence as defined by age norms was evaluated in two independent investigations. Study I was a within-subject evaluation using an alternating treat...

Lexical constraints in phonological acquisition.

Lexical diffusion, as characterized by interword variation in production, was examined in phonological acquisition. The lexical variables of word frequency and neighbourhood density were hypothesized to facilitate sound change to varying degrees. Twelve children with functional phonological delays, aged 3;0 to 7;4, participated in an alternating treatments experiment to promote sound change. Independent variables were crossed to yield all logically possible combinations of high/low frequency and high/low density in treatment; the dependent measure was generalization accuracy in production. Results indicated word frequency was most facilitative in sound change, whereas, dense neighbourhood structure was least facilitative. The salience of frequency and avoidance of high density are discussed relative to the type of phonological change being induced in childrens grammars, either phonetic or phonemic, and to the nature of childrens representations. Results are further interpreted with reference to interactive models of language processing and optimality theoretic accounts of linguistic structure.

Long-distance place assimilation with an interacting error pattern in phonological acquisition

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Applications of learnability theory to clinical phonology

This paper provides a tutorial on the selection of complex target sounds for treatment following from known principles of language learnability. The focus is on syllable structure in recommending onset consonant clusters for treatment. The step-by-step procedure of cluster selection is illustrated for one child, Jarrod, who presented with a phonological disorder. Target selection procedures are guided by universal principles that govern the phonotactics of onset clusters and experimental evidence that supports the efficacy of phonologically complex targets. The prediction is that treatment of onset clusters will facilitate Jarrods learning of both complex and simple properties of the sound system.

Age of word acquisition effects in treatment of children with phonological delays

The effects of the age of acquisition (AoA) of words were examined in the clinical treatment of 10 preschool children with phonological delays. Using a single-subject multiple-baseline experimental design, children were enrolled in one of four conditions that varied the AoA of the treated words (early vs. late acquired) relative to their corresponding word frequency (high vs. low frequency). Phonological generalization to treated and untreated sounds in error served as the dependent variable. Results showed that late acquired words induced greater generalization, with an effect size four times greater than early acquired words, whereas the effects of word frequency were minimized. Results are discussed relative to hypotheses about the role of AoA in language acquisition and the relevance of this variable for phonological learning.

Lexical characteristics of sound change.

The purpose of this study was to determine the relationship between sound change and lexical structure in two children with functional phonological disorders. Specifically, the question of how sound change infuses through the developing lexicon was addressed. A chronology of phonemic acquisition for the children who participated has previously been documented. These archival data were now extended to evaluate lexical change relative to sounds acquired. Lexical change was examined through the parameters of neighbourhood density and word frequency. Results of this study revealed two converging patterns across children: (a) for each child there was one parameter (neighbourhood density or word frequency) of lexical change which held across all sounds acquired, and (b) for each child the alternative parameter patterned differentially by sound. This variability in lexical change was hypothesized to be associated with the relative degree of feature specification of the sounds acquired. This has theoretical implications for the overlay of phonological and lexical structure, and clinical potential for remediation of phonological disorders.

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.

Effect Size for Single-Subject Design in Phonological Treatment

PURPOSE The purpose of this study was to document, validate, and corroborate effect size (ES) for single-subject design in treatment of children with functional phonological disorders; to evaluate potential child-specific contributing variables relative to ES; and to establish benchmarks for interpretation of ES for the population. METHOD Data were extracted from the Developmental Phonologies Archive for 135 preschool children with phonological disorders who previously participated in single-subject experimental treatment studies. Standard mean difference(all with correction for continuity) was computed to gauge the magnitude of generalization gain that accrued longitudinally from treatment for each child with the data aggregated for purposes of statistical analyses. RESULTS ES ranged from 0.09 to 27.83 for the study population. ES was positively correlated with conventional measures of phonological learning and visual inspection of learning data on the basis of procedures standard to single-subject design. ES was linked to childrens performance on diagnostic assessments of phonology but not other demographic characteristics or related linguistic skills and nonlinguistic skills. Benchmarks for interpretation of ES were estimated as 1.4, 3.6, and 10.1 for small, medium, and large learning effects, respectively. CONCLUSION Findings have utility for single-subject research and translation of research to evidence-based practice for children with phonological disorders.

Effect Size in Clinical Phonology.

The purpose of this article is to motivate the use of effect size (ES) for single-subject research in clinical phonology, with an eye towards meta-analyses of treatment effects for children with phonological disorders. Standard mean difference (SMD) is introduced and illustrated as one ES well suited to the multiple baseline (MBL) design and evaluation of generalization learning, both of which are key to experimental studies in clinical phonology.

Phonological learning and lexicality of treated stimuli.

The purpose was to evaluate the lexicality of treated stimuli relative to phonological learning by preschool children with functional phonological disorders. Four children were paired in a single-subject alternating treatments design that was overlaid on a multiple baseline across subjects design. Within each pair, one child was taught one sound in real words and a second sound in non-words; for the other child of the pair, lexicality was reversed and counterbalanced. The dependent variable was production accuracy of the treated sounds as measured during the session-by-session course of instruction. Results indicated that production accuracy of the treated sound was as good as or better using non-word as opposed to real word stimuli. The clinical implications are considered, along with potential accounts of the patterns of learning.