Abstract
Background: Children with specific language impairments (SLI) repeat nonwords less accurately than typically developing children, suggesting a phonological deficit. Much work has attempted to explain these results in terms of a phonological memory deficit. However, subsequent work revealed that these results might be explained better as a deficit in phonological sensitivity.
Aims: This study used a nonword repetition task to examine how children with SLI extract phonological regularities from their language input.
Methods & Procedures: Eighteen English-speaking children with SLI (7;3–10;6) and 18 age-matched controls participated in two English nonword repetition tasks. Three- and four-syllable nonwords varied in a single phonotactic frequency manipulation, either consonant frequency or phoneme co-occurrence frequency, while all other factors were held constant. Repetitions were scored in terms of accuracy as either the percentage of phonemes correctly produced or phoneme co-occurrences (diphones) correctly produced. In addition, onset-to-onset reaction times and repetition durations were measured.
Outcomes & Results: Accuracy results revealed significant group, length, and phonotactic frequency effects. Children with SLI repeated nonwords less accurately than age-matched peers, and all children repeated three-syllable nonwords and those with higher frequency phonotactic patterns more accurately. However, phonotactic frequency by group interactions were not significant. Timing results were mixed, with group reaction time differences for co-occurrence frequency, but not consonant frequency, and no group repetition duration differences.
Conclusions & Implications: While children with SLI were less accurate overall, non-significant interactions indicate that both groups of children were comparably affected by differences in consonant and diphone frequency.
Acknowledgements
This research was supported by grants from NIDCD: DC-05263 to the first author; DC-005650 to the second author; and DC-04072 to the third author. We are grateful to the children and their parents for participating. We thank Lisbeth Simon, Elina Mainela-Arnold, and Kristin Ryan for help with standardized testing, Ariel Young Shibilski for recording the stimuli, and Elizabeth Berkowitz, Heather DeFelice, Karissa Fronk, Emily Harms, Stacy Markovitz, Stephanie Pesa, and Anne Stephens for transcribing children's repetitions.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.
Notes
1. Because the nonwords in Dollaghan and Campbell's NWR task are minimally word-like (low phonotactic probability), it typically is used as a measure of phonological working memory, but cannot be used to assess sensitivity to probabilistic phonotactic structure.
2. English syllabification rules state that each vowel within a word serves as a syllable nucleus. Preceding consonants are then attached to vowels as syllable onsets. A vowel can take as many consonants as are permitted by phonotactic rules. Finally, any remaining consonants are attached as coda consonants (Kahn Citation1980). In some cases, vowel quality affects syllabification such that a single consonant serves both to close a preceding syllable and to open a following syllable, that is, it is ambisyllabic. Tense vowels such as /aI/ in ‘bye’ can close a syllable and so do not require a coda consonant.
But lax vowels such as /I/ in ‘bit’ cannot close a syllable and so must be followed by a coda consonant. Consider two bisyllabic words ‘biker’ and ‘bicker’. ‘Biker’ contains a tense vowel, and so there is a clear syllable boundary between it and the following consonant. ‘Bicker’ on the other hand contains a lax vowel that must be followed by a consonant. In this case, the single word-medial consonant simultaneously closes the first syllable and opens the second. While the consonant attaches to both syllables, it is only a single consonant of no longer duration than a similar consonant that attaches to a single syllable. This ambisyllabicity will necessarily affect how phonotactic frequency is calculated