EBP Compendium: Summary of Systematic Review
Natural Sciences and Engineering Research Council of Canada
The Double-Deficit Hypothesis: A Comprehensive Analysis of the Evidence
Vukovic, R. K., & Siegel, L. S.
(2006).
Journal of Learning Disabilities, 39(1), 25-47.
Indicators of Review Quality:
|
The review addresses a clearly focused question
| Yes |
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Criteria for inclusion of studies are provided
| Yes |
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Search strategy is described in sufficient detail for replication
| Yes |
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Included studies are assessed for study quality
| No |
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Quality assessments are reproducible
| No |
Description: This is a systematic review of peer-reviewed studies examining the naming speed and phonological processing skills of individuals with developmental dyslexia in order to investigate the double-deficit hypothesis theory.
Question(s) Addressed:
(The following questions were discussed in the article. Each was used as a topic heading in the results section.)
- Is dyslexia characterized by naming speed difficulties?
- What is naming speed's contribution of independent variance to reading ability?
- Should naming speed by characterized independently from phonological awareness?
- What is the nature of the relationship between naming speed and reading development?
- What does the extant research conclude about the three subtypes?
- Who is slow on RAN?
- What is the efficacy of interventions for dyslexia?
Population: Individuals with dyslexia or reading difficulties
Intervention/Assessment: Studies designed to test or investigate the double-deficit hypothesis of developmental dyslexia (In the double-deficit hypothesis, both naming speed deficits and phonological skill deficits exist in an individual)
Number of Studies Included: 36
Years Included: Not stated
Findings:
Conclusions:
- Assessment/Diagnosis
- Assessment Areas
- Reading
- The evidence for the double-deficit hypothesis suggesting that reading impairment is a result of independent deficits in naming speed and phonological processing remains inconclusive.
- Overall, evidence from the included studies suggest that naming speed deficits are characteristic of a subset of individuals with dyslexia, generally the more severe dyslexic individuals. "[H]owever, the question of whether naming speed deficits characterize dyslexia is largly unresolved" (p. 35).
- Treatment
- Language
- Reading - "The hypothesis that children with a naming speed deficit would not benefit from phonlogical interventions in not supported" (p. 45).
Keywords: Literacy, Language Disorders, Written Language Disorders
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Added to Compendium: March 2012