http://orcid.org/0000-0002-0311-3524
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ABSTRACT
A single case study is reported of a 10-year-old, English-speaking boy, L.S., who presented with spelling errors similar to those described in acquired graphemic buffer dysgraphia (GBD). We used this case to evaluate the appropriateness of applying adult cognitive models to the investigation of developmental cognitive disorders. The dual-route model of spelling guided this investigation. L.S. primarily made “letter errors” (deletions, additions, substitutions, transpositions, or a combination of these errors) on words and nonwords and in all input (aural and visual) and output modalities (writing, typing, oral spelling); there was also some evidence of a length effect and U-shaped serial position curve. An effect of lexical variables on spelling performance was also found. We conclude that the most parsimonious account is an impairment at the level of the graphemic buffer and without systematic cognitive neuropsychological investigation, the nature of L.S.’s spelling difficulty would likely have been missed.
Acknowledgements
We are very grateful to L.S. and his mother, and to the control participants and their families, for their participation in this study. We are also grateful to Trudy Krajenbrink, Yvette Kezilas, Nathan Caruana, Naama Friedmann, Teresa Schubert, Greg Savage, and reviewers for valuable discussions and feedback. Many thanks to Nicholas Badcock and Kathryn Preece for their assistance in recruitment.
Disclosure statement
No potential conflict of interest was reported by the authors.
ORCID
Lyndsey Nickels http://orcid.org/0000-0002-0311-3524
Notes
1 Significantly higher proportions of letter position errors in reading have been suggested to indicate a deficit in the orthographic analyser (e.g., Friedmann & Rahamim, Citation2007; Kezilas et al., Citation2014; Kohnen et al., Citation2012). Some of L.S.’s reading mistakes on the nonwords were letter position errors (e.g., reading salpy as “slappy”), possibly indicating that the suggested impairment of the orthographic analyser impacted on word and nonword reading.
2 In all spelling tasks for this investigation, self-corrections were accepted if they occurred before the examiner administered the next item.
3 Given that L.S.’s performance on standardized spelling tests were within normal limits, the reader may wonder whether L.S. has a “deficit” at all. We will demonstrate that indeed L.S.’s performance on a number of tasks was qualitatively different from that of his peers, indicating a dysfunctioning graphemic buffer. We will return to the puzzle of his “deficit” in the General Discussion.
4 The QUIL (Dodd et al., Citation1996) was chosen as a selection measure as it is one of the purest measures of nonlexical spelling knowledge with Australian normative data (Kohnen, Nickels & Castles, Citation2009). The TWS–3 was used to assess lexical spelling skills as it was reviewed as the most appropriate measure available (Kohnen et al., Citation2009).
5 All examples presented are from L.S.’s written samples.
6 Spelling responses were considered phonologically plausible if each phoneme in the target corresponded to a grapheme in the response as reported by PGC rules used by Perry, Ziegler, and Coltheart (Citation2002). Any ambiguities were resolved through discussion between authors.
7 Substitutions of irregular homophones could also be classified as phonologically plausible or whole-word substitution errors. We always classified these as homophone substitutions.
8 We also asked L.S. to read these 182 words aloud. He read 91% correctly, suggesting that L.S. was familiar with the written form for most of the words presented in this spelling task.
9 Regularity was coded based on the predictability of PGCs within each word. Predictability was defined in reference to the work by Perry et al. (Citation2002). A rating of 1 indicates that all phonemes in a word are spelled using the most frequent spelling for a phoneme on the Perry list (e.g., RING). A rating of 0 indicates that one or more phonemes in a word are spelled not using the most frequent spelling on the Perry list (e.g., SIGN).
10 Criteria for phonologically plausible spelling as outlined above in spelling error scoring procedure.
11 While naming agreement was high for these pictures, some ambiguity remained even in adults for whom this task was designed originally.
12 Five of the seven control children were available for this follow-up experimental testing.
13 Specifically, orthographic neighbourhood size was significantly and strongly negatively correlated with number of letters (word length), r = −.619, p < .0001, two-tailed. Number of letters was also significantly correlated with age of acquisition r = .204, p < .0001, two-tailed; regularity r = −.256, p < .0001, two-tailed; and with written frequency r = −.188, p < . 0001, two-tailed; however, it was not correlated with imageability, r = .025, p = .656, two-tailed (see , for more details).
14 Readers are reminded that the term “letter errors” refers to when a word was coded as containing an error that is typical in cases of GBD. “Individual letter accuracy” refers to the accuracy of an individual letter within a word.