The Double-Deficit Hypothesis

Department of Educational Psychology, University of British Columbia, Vancouver.
Journal of Learning Disabilities (Impact Factor: 1.9). 02/2006; 39(1):25-47. DOI: 10.1177/00222194060390010401
Source: PubMed


The double-deficit hypothesis of developmental dyslexia proposes that deficits in phonological processing and naming speed represent independent sources of dysfunction in dyslexia. The present article is a review of the evidence for the double-deficit hypothesis, including a discussion of recent findings related to the hypothesis. Studies in this area have been characterized by variability in methodology--how dyslexia is defined and identified, and how dyslexia subtypes are classified. Such variability sets limitations on the extent to which conclusions may be drawn with respect to the double-deficit hypothesis. Furthermore, the literature is complicated by the persistent finding that measures of phonological processing and naming speed are significantly correlated, resulting in a statistical artifact that makes it difficult to disentangle the influence of naming speed from that of phonological processing. Longitudinal and intervention studies of the double-deficit hypothesis are needed to accumulate evidence that investigates a naming speed deficit that is independent of a phonological deficit for readers with dyslexia. The existing evidence does not support a persistent core deficit in naming speed for readers with dyslexia.

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    • "The LA is understood as part of the speed of information processing (Wagner & Torgesen, 1987). Studies claim that the AL is associated with reading, especially in decoding skills, fluency and comprehension (Wagner et al., 1997; Wolf & Bowers, 1999; Brizzolara et al., 2006; Vukovic & Siegel, 2006; Miranda-Casas et al., 2010). "
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    ABSTRACT: Purpose: The objective of this study was to compare the performance of Phonological Processing (Phonological Awareness, Lexical Acess and Working Memory) between children with ADHD and children with typical development. Methods: Participated in this study, 30 school aged children of both genders aged between 9-12 years, divided into 2 groups: Experimental Group (EG), 15 children with ADHD combined type and, Control Group (CG), 15 children with typical development , who attended elementary school in public and private education. The instruments utilized were: Phonological Awareness Test—Sequential Assessment Tool (CONFIAS); Rapid automatic Naming Testd); and Proof of repetition of nonsense words (Kessler, 1997). Results: The results revealed differences between in the instruments used. Conclusion: Regarding the performance of Phonological Processing, the children with ADHD showed lower performance in Phonological Awareness, Access to Lexical and Phonological Memory compared to children with typical development .
    Full-text · Article · Sep 2015 · Psychology
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    • "While these two skills , RAN and sight reading , seem to go together , some people have trouble with sight reading but can name non - word visual stimuli as quickly as typical readers , which poses additional questions . Vukovic and Siegal ( 2006 ) performed a comprehensive review of the double - deficit hypothesis . They looked for evidence in past research of the three possible subtypes of dyslexia mentioned above , but the definition of " dyslexic readers " in the 29 studies they included in their review varied from a lack of definition , " Dyslexia not defined ; boys selected from a pool of 56 children referred for dyslexia who showed ' unusual hesitancy ' in rapidly naming a series of colors " to lags in oral reading skill , to word reading percentile scores . "
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    ABSTRACT: This research attempted to document a positive correlation between the life-long phonological processing deficit such as in developmental dyslexia and arithmetic fact fluency deficit. Previous research has shown a possible connection. These deficits continue into adulthood and continue to affect behavior, reading, and general functioning. This research failed to obtain a large enough sample size to make meaningful conclusions; however, unlike previous research designs, this research design is relatively easy to replicate. By preserving our data, we have made it possible for other researchers to continue to grow the sample size. This bodes well for the future because researchers interested in how developmental dyslexia affects adults may continue to add to the database and we will be able to draw meaningful conclusions regarding the lifetime connection between phonological processing deficits and arithmetic fact fluency deficits.
    Full-text · Thesis · May 2015
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    • "An influential theoretical framework involving both processes is Wolf and Bowers's (1999) Double Deficit Hypothesis (DDH), which predicts that RAN and PA constitute more or less independent correlates of WR ability. Since the introduction of the DDH, this assumption has been affirmed on numerous occasions (e.g., Compton, DeFries, & Olson, 2001; Kirby et al., 2010; Papadopoulos, Georgiou, & Kendeou, 2009; Schatschneider, Carlson, Francis, Foorman, & Fletcher, 2002; Torppa, Georgiou, Salmi, Eklund, & Lyytinen, 2012; Torppa et al., 2013; Vukovic & Siegel, 2006). The DDH also predicts that a combination of deficient RAN and PA—a " double deficit " —is associated with the poorest level of WR performance (Wolf & Bowers, 1999, p. 424). "
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    ABSTRACT: In this study word reading (WR) fluency was used to dichotomously classify 1,598 Dutch children at different cutoffs, indicating (very) poor or (very) good reading performance. Analysis of variance and receiver operating characteristics were used to investigate the effects of rapid automatized naming (RAN) and phonemic awareness (PA) in predicting group membership. The highest predictive values were found for the combination of RAN and PA, particularly for the poorest readers. Furthermore, results indicate that with the severity of impairment, WR is more dominated by deficient PA, which is interpreted as an enduring problem with sublexical processing. Another main result is that with the increase of reading skill, the contribution of PA diminishes, whereas the contribution of RAN remains fairly constant for the whole reading fluency continuum. These results warrant the conclusion that whereas PA hallmarks reading disability, RAN appears to be the default predictor for above-average or excellent reading proficiency.
    Full-text · Article · Apr 2015 · Scientific Studies of Reading
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