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 children's 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.

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.

Unraveling phonological conspiracies: A case study.

This paper focuses on three seemingly unrelated error patterns in the sound system of a child with a phonological delay, Child 218 (male, age 4 years 6 months) and ascribes those error patterns to a larger conspiracy to eliminate fricatives from the phonetic inventory. Employing Optimality Theory for its advantages in characterizing conspiracies, our analysis offers a unified account of the observed repairs. The contextual restrictions on those repairs are, moreover, attributed to early developmental prominence effects, which are independently manifested in another error pattern involving rhotic consonants. Comparisons are made with a published case study involving a different implementation of the same conspiracy, the intent being to disambiguate the force behind certain error patterns. The clinical implications of the account are also considered.

How to meet the neighbors: Modality effects on phonological generalization.

Long-term auditory priming of words from dense neighborhoods has been posited as a learning mechanism that affects change in the phonological structure of children's lexical representations. An apparent confound associated with the modality of priming responsible for structural change has been introduced in the literature, which challenges this proposal. Thus, our purpose was to evaluate prime modality in the treatment of children with phonological delay. Nine children were assigned to auditory-visual, auditory, or visual priming of words from dense neighborhoods prior to the treatment of production as the independent variable. The dependent variable was phonological generalization. Results showed that auditory priming (with or without visual input) promoted greater generalization on an order of magnitude of 3:1. Findings support the theoretical significance of auditory priming for phonological learning and demonstrate the applied utility of priming in clinical treatment.

The coronal fricative problem.

This paper examines a range of predicted versus attested error patterns involving coronal fricatives (e.g. [s, z, θ, ð]) as targets and repairs in the early sound systems of monolingual English-acquiring children. Typological results are reported from a cross-sectional study of 234 children with phonological delays (ages 3 years; 0 months to 7;9). Our analyses revealed different instantiations of a putative developmental conspiracy within and across children. Supplemental longitudinal evidence is also presented that replicates the cross-sectional results, offering further insight into the life-cycle of the conspiracy. Several of the observed typological anomalies are argued to follow from a modified version of Optimality Theory with Candidate Chains (McCarthy, 2007).

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.

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 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.

On the interaction of deaffrication and consonant harmony.

Error patterns in children's phonological development are often described as simplifying processes that can interact with one another with different consequences. Some interactions limit the applicability of an error pattern, and others extend it to more words. Theories predict that error patterns interact to their full potential. While specific interactions have been documented for certain pairs of processes, no developmental study has shown that the range of typologically predicted interactions occurs for those processes. To determine whether this anomaly is an accidental gap or a systematic peculiarity of particular error patterns, two commonly occurring processes were considered, namely Deaffrication and Consonant Harmony. Results are reported from a cross-sectional and longitudinal study of twelve children (age 3 ; 0-5 ; 0) with functional phonological delays. Three interaction types were attested to varying degrees. The longitudinal results further instantiated the typology and revealed a characteristic trajectory of change. Implications of these findings are explored.

On the anatomy of a chain shift.

Phonological chain shifts have been the focus of many theoretical, developmental, and clinical concerns. This paper considers an overlooked property of the problem by focusing on the typological properties of the widely attested 's > θ > f' chain shift involving the processes of Labialization and Dentalization in early phonological development. Findings are reported from a cross-sectional study of 234 children (ages 3 years; 0 months-7;9) with functional (nonorganic) phonological delays. The results reveal some unexpected gaps in the predicted interactions of these processes and are brought to bear on the evaluation of recent optimality theoretic proposals for the characterization of phonological interactions. A developmental modification to the theory is proposed that has the desired effect of precluding certain early-stage grammars. The proposal is further evaluated against the facts of another widely cited developmental chain shift known as the 'puzzle > puddle > pickle' problem (Smith 1973).

On the interaction of velar fronting and labial harmony.

This article documents the typological occurrence and interactions of two seemingly independent error patterns, namely Velar Fronting and Labial Harmony, in a cross-sectional investigation of the sound systems of 235 children with phonological delays (ages 3;0 to 7;9). The results revealed that the occurrence of Labial Harmony depends on the occurrence of Velar Fronting, and that, when these processes co-occurred, all three predicted types of interactions were attested. A constrained version of Optimality Theory is put forward that offers a unified explanation for the implicational relationship between these error patterns and their observed interactions. The findings are compared with the results from other studies and are considered for their theoretical and clinical implications.

Nonwords and generalization in children with phonological disorders.

PURPOSE: To evaluate the effects of using nonword (NW) stimuli in treatment of children with phonological disorders relative to real words (RWs). METHODS: Production data from 60 children were examined retrospectively. Thirty of the participants were previously treated on sounds in error using NWs, and the other 30 had been treated using RWs. Generalization was the dependent variable, with measurement of accurate production of treated and untreated sounds immediately posttreatment and longitudinally following the withdrawal of treatment. RESULTS: Under both stimulus conditions, and at both sampling points in time, there was greater generalization to treated sounds compared with untreated. NWs, as opposed to RWs, induced greater, more rapid systemwide generalization as a function of treatment. Children exposed to NWs sustained those levels of performance even after treatment was withdrawn. Children exposed to RWs eventually reached comparable levels of phonological generalization, but not until 55 days after the cessation of treatment. CONCLUSION: The findings support the ecological validity of NWs in phonological treatment. The differential results hint that NWs may benefit treatment efficacy and efficiency, but this remains to be determined through prospective study. Consideration is given to a potential theoretical account of the NW effects, with appeal to the literature on novel word learning.

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.

The Lexicon and Phonology: Interactions in Language Acquisition.

The purpose of this paper is to underscore the importance of the link between lexical and phonological acquisition by considering learning by children beyond the 50-word stage and by applying cognitive models of spoken word processing to development. Lexical and phonological variables that have been shown to influence perception and production across the lifespan are considered relative to their potential role in learning by preschool children. The effect of these lexical and phonological variables on perception, production, and learning are discussed in the context of a two-representation connectionist model of spoken word processing. The model appears to offer insights into the complex interaction between the lexicon and phonology and may be useful for clinical diagnosis and treatment of children with language delays.

Lexical organization and phonological change in treatment.

Word frequency and neighborhood density are properties of lexical organization that differentially influence spoken-word recognition. This study examined whether these same properties also affect spoken-word production, particularly as related to children with functional phonological delays. The hypothesis was that differential generalization would be associated with a word's frequency and its neighborhood density when manipulated as input in phonological treatment. Using a multiple baseline across subjects design, 8 children (aged 3;10 to 5;4) were randomly enrolled in 1 of 4 experimental conditions targeting errored sounds in high-frequency, low-frequency, high-density, or low-density words. Dependent measures were generalization of treated sounds and untreated sounds within and across manner classes as measured during and following treatment. Results supported a hierarchy of phonological generalization by experimental condition. The clinical implications lie in planning for generalization through the input presented in treatment. Theoretically, the results demonstrate that lexical organization of words in the mental lexicon interacts with phonological structure in learning.