D / Naming pictures of polysyllabic words (three or more syllables (PSWs)) seems to provide speech pathologists with information about communication status not necessarily present when naming pictures of short words (monosyllabic words (MSWs) and di-syllabic words (DSWs)). Typically developing children and children with speech, language and literacy impairments err on PSWs even when short words are accurate. In this study, typical behaviour of PSW production was delimited and a model of PSW acquisition was developed because if erroneous PSWs mark impairment, then circumscribing the tolerances of them in typically developing speech is necessary to differentiate it from impairment. A proportional stratified, cluster sampling procedure was used to locate 354 children, aged 3;0 to 7;11 years, of whom 283 met the selection criteria, including normal hearing, language and cognition. All English phonemes were repeatedly sampled in 166 words, elicited through picture naming, that were varied for syllable number, stress and shape. Syllable, age and interaction effects were present with more mismatches in PSWs than in short words, decreasing with increasing age. Mismatches were captured in five a priori patterns of deletions, additions and reordering of syllables and segments in words as well as alterations of consonants or vowels in words that preserved the phonotactic shape. However, as all five patterns were word-specific, each affecting a core group of words containing PSWs and DSWs, the syllable effect was modified. It appeared to be a proxy for a complex interaction between segmental and prosodic features common to the core words that included non-final weak syllables, within-word consonant sequences that required labial-velar movements, velar and sonorant sounds and sounds that shared place or manner features, severally or together. The production changes conformed to the predictions of the model of PSW acquisition. These changes reflected alterations in the phonological representation, motor planning and motor execution skills aspects of the speech processing system. The phonological representation, changing from holistic to fine-grained, was argued as the key change because information for motor planning and execution was liberated that culminated in increased accuracy. If children’s productions of the PSWs used in this study exceed the tolerances defined in this thesis, impairment may be indicated. Future research is needed to determine that possibility.

D / Naming pictures of polysyllabic words (three or more syllables (PSWs)) seems to provide speech pathologists with information about communication status not necessarily present when naming pictures of short words (monosyllabic words (MSWs) and di-syllabic words (DSWs)). Typically developing children and children with speech, language and literacy impairments err on PSWs even when short words are accurate. In this study, typical behaviour of PSW production was delimited and a model of PSW acquisition was developed because if erroneous PSWs mark impairment, then circumscribing the tolerances of them in typically developing speech is necessary to differentiate it from impairment. A proportional stratified, cluster sampling procedure was used to locate 354 children, aged 3;0 to 7;11 years, of whom 283 met the selection criteria, including normal hearing, language and cognition. All English phonemes were repeatedly sampled in 166 words, elicited through picture naming, that were varied for syllable number, stress and shape. Syllable, age and interaction effects were present with more mismatches in PSWs than in short words, decreasing with increasing age. Mismatches were captured in five a priori patterns of deletions, additions and reordering of syllables and segments in words as well as alterations of consonants or vowels in words that preserved the phonotactic shape. However, as all five patterns were word-specific, each affecting a core group of words containing PSWs and DSWs, the syllable effect was modified. It appeared to be a proxy for a complex interaction between segmental and prosodic features common to the core words that included non-final weak syllables, within-word consonant sequences that required labial-velar movements, velar and sonorant sounds and sounds that shared place or manner features, severally or together. The production changes conformed to the predictions of the model of PSW acquisition. These changes reflected alterations in the phonological representation, motor planning and motor execution skills aspects of the speech processing system. The phonological representation, changing from holistic to fine-grained, was argued as the key change because information for motor planning and execution was liberated that culminated in increased accuracy. If children’s productions of the PSWs used in this study exceed the tolerances defined in this thesis, impairment may be indicated. Future research is needed to determine that possibility.