Phonological core in dyslexia

In Archives of Clinical Neuropsychology, Michelle Kibby published the results of a study examining the relationships among measures of short-term memory and dyslexia. In two studies involving children ages 9-13 with and without dyslexia (defined on the basis of discrepancy; > 1 SD difference between IQ and word identification) she found results that are consistent with the theory that the primary problem for children with reading problems is in phonological processing.

The goals of this project were threefold: to determine the nature of the memory deficit in children/adolescents with dyslexia, to utilize clinical memory measures in this endeavor, and to determine the extent to which semantic short-term memory (STM) is related to basic reading performance. Two studies were conducted using different samples, one incorporating the Wide Range Assessment of Memory and Learning and the other incorporating the California Verbal Learning Test-Children’s Version. Results suggest that phonological STM is deficient in children with dyslexia, but semantic STM and visual – spatial STM are intact. Long-term memory (LTM) for both visual and verbal material also is intact. Regarding reading performance, semantic STM had small correlations with word identification and pseudo-word decoding across studies despite phonological STM being moderately to strongly related to both basic reading skills. Overall, results are consistent with the phonological core deficit model of dyslexia as only STM was affected in dyslexia and related to basic reading skill.

Professor Kibby’s samples were relatively small (20 in each group in the first study and 18 in each in the second study), making it more impressive that the results were as strong as they were. Also, although I suspect that the measures used in this study have limited clinical utility, it is impressive that they pointed in the same direction as other analyses of reading problems.

Kibby, M. Y. (2009). Memory functioning in developmental dyslexia: An analysis using two clinical memory measures. Archives of Clinical Neuropsychology, 24, 245-254. [doi:10.1093/arclin/acp028]

2 Responses to “Phonological core in dyslexia”

  • Just a thought , maybe STM phonological problems are related more to the phonological problems rather than the STM. Surely STM can be measured other than phonologically.

    Maybe I missed the point but I see a problem measuring STM with the known phonological problems and concluding that it is STM.

  • Mr. Hayes, that’s a good point. There would likely be variance shared between two measures based on how they were assessed. If both are assessed using phonological tasks, then at least part of the shared variance would like be attributable to the fact that STM was assessed with phonologic tasks (e.g., digit span backwards). It would be important to partial out the correlation attributable to that factor. I don’t recall how Professor Kibby adjusted for this…not enough time to go back to the details right now. If you read it closely and find out more, please drop another comment.

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