Verbal and non-verbal fluency in adults with developmental dyslexia: Phonological processing or executive control problems?

Smith-Spark, J. H., Henry, L., Messer, D. J. & Zięcik, A. P. (2017). Verbal and non-verbal fluency in adults with developmental dyslexia: Phonological processing or executive control problems?. Dyslexia,

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Abstract

The executive function of fluency describes the ability to generate items according to specific rules. Production of words beginning with a certain letter (phonemic fluency) is impaired in dyslexia, whilst generation of words belonging to a certain semantic category (semantic fluency) is typically unimpaired. However, in dyslexia, verbal fluency has generally been studied only in terms of overall words produced. Furthermore, performance of adults with dyslexia on non-verbal design fluency tasks has not been explored but would indicate whether deficits could be explained by executive control, rather than phonological processing, difficulties. Phonemic, semantic, and design fluency tasks were presented to adults with dyslexia and without dyslexia, using fine-grained performance measures and controlling for IQ. Hierarchical regressions indicated that dyslexia predicted lower phonemic fluency, but not semantic or design fluency. At the fine-grained level, dyslexia predicted a smaller number of switches between subcategories on phonemic fluency, whilst dyslexia did not predict the size of phonemically-related clusters of items. Overall, the results suggested that phonological processing problems were at the root of dyslexia-related fluency deficits; however, executive control difficulties could not be completely ruled out as an alternative explanation. Developments in research methodology, equating executive demands across fluency tasks, may resolve this issue.

Item Type: Article
Additional Information: This is the peer reviewed version of the following article: Smith-Spark, JH, Henry, LA, Messer, DJ & Zięcik, AP (2017). Verbal and non-verbal fluency in adults with developmental dyslexia: Phonological processing or executive control problems?. Dyslexia, which is to be published in final form at http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1099-0909/. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.
Uncontrolled Keywords: Developmental Dyslexia; Naming Fluency; Verbal Fluency; Design Fluency; Adult Cognition; Executive Functioning
Subjects: H Social Sciences > HV Social pathology. Social and public welfare
P Language and Literature > P Philology. Linguistics
Divisions: School of Health Sciences > Department of Language & Communication Science
URI: http://openaccess.city.ac.uk/id/eprint/17329

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