Polysyllable maturity of preschool children with speech sound disorders

Polysyllables are words of three or more syllables and contain multiple consonants and vowels as well as complex syllable shapes and stress patterns. Polysyllables may provide a more comprehensive view of preschool children's phonological representations than mono- or di-syllabic words because they are complex and more prone to error. Children with speech sound disorders (SSD) find polysyllables challenging but there is little consensus about the best methods for analysing and interpreting children's productions. Early SSD can have a long-lasting impact on speech production, phonological processing, and literacy into adulthood so there is a need to refine assessment and analysis methods for children with SSD to identify those children who may require additional support. The purpose of this thesis is to inform the clinical practice of speech-language pathologists through a multi-faceted investigation of polysyllables in preschool children with SSD. To achieve this purpose, five aims were addressed: (1) to develop a method of analysing polysyllables suitable for children with SSD, (2) to present a framework for interpreting polysyllable maturity of children with SSD, (3) to describe polysyllable errors made by preschool children with SSD using three measures of polysyllables: segmental accuracy (PCC, PVC, and PPC), frequency of errors, and polysyllable maturity, (4) to investigate of the progression of polysyllable maturity in children with SSD over time, including factors that influence improvements in maturity, and (5) to explore the relationship between polysyllable speech accuracy and emergent literacy skills in preschool children with SSD. To achieve these aims, data were collected from 93 preschool children with SSD who participated in the Sound Start Study, a cluster randomized controlled trial investigating the effectiveness of an input-based computer intervention for children with SSD. The children were aged 4;0-5;5 at the beginning of the research and presented with a phonologically-based SSD of unknown origin. All participants completed speech production, phonological processing, and emergent literacy tasks. Eighty of the participating children completed the polysyllable speech production task (POP, Baker, 2013) on three occasions over a 14-22 week period. This thesis includes six published or submitted papers that present reviews and research studies. The first paper is a book chapter that provides an overview of phonology. The second paper presents a systematic search and review of literature that has examined polysyllable assessment and analysis of young children aged 7;11 years or under. This second paper describes the development of (1) the Word-level Analysis of Polysyllables (WAP, Masso, 2016a) including seven categories of error; and (2) the Framework of Polysyllable Maturity (Framework, Masso, 2016b) including 5-levels (A-E) of maturity. The third and subsequent papers focus specifically on children of preschool age. The third paper applies the WAP and the Framework to speech samples from 93 preschool children with SSD and documents that preschool children with SSD have difficulty saying polysyllables accurately. The findings also highlight that vowels are less likely to be accurate on a polysyllable task than a primarily mono- and di-syllabic speech task. The fourth paper describes preschool children's longitudinal progression of polysyllable maturity (from Levels A to E) across three points in time and highlights that preschool children who demonstrate the second lowest level of polysyllable maturity (Framework Level B) on initial assessment are 8.62 times more likely to improve polysyllable maturity than preschool children who demonstrate the least mature polysyllables (Framework Level A). The later chapters of this thesis explore the relationship between SSD, phonological processing, and emergent literacy skills.