Individual prediction of dyslexia by single versus multiple deficit models.

Abstract

The overall goals of this study were to test single vs. multiple cognitive deficit models of dyslexia (reading disability) at the level of individual cases and to determine the clinical utility of these models for prediction and diagnosis of dyslexia. To accomplish these goals, we tested five cognitive models of dyslexia: two single-deficit models, two multiple-deficit models, and one hybrid model in two large population-based samples, one cross-sectional (Colorado Learning Disability Research Center—CLDRC) and one longitudinal (International longitudinal Twin Study—ILTS). The cognitive deficits included in these cognitive models were in phonological awareness, language skill, and processing speed and/ or naming speed. To determine whether an individual case fit one of these models, we used two methods: 1) the presence or absence of the predicted cognitive deficits, and 2) whether the individual’s level of reading skill best fit the regression equation with the relevant cognitive predictors (i.e. whether their reading skill was proportional to those cognitive predictors.) We found that roughly equal proportions of cases met both tests of model fit for the multiple deficit models (30–36%) and single deficit models (24–28%); hence, the hybrid model provided the best overall fit to the data. The remaining roughly 40% of cases in each sample lacked the deficit or deficits that corresponded with their best fitting regression model. We discuss the clinical implications of these results for both diagnosis of school age children and preschool prediction of children at risk for dyslexia.

Differences in the intellectual profile of children with intellectual vs. learning disability

“…It has been demonstrated that many predictors should be considered for an accurate diagnosis of SLD (Pennington et al, 2012). There is also an abundance of evidence indicating that a deficit in the basic cognitive processes can predict response to intervention (Al Otaiba & Fuchs, 2002;Frijters et al, 2011).…”

Neuropsychological characteristics of dyslexic children

“…Findings that dyslexia is a complex disorder, associated to heterogeneous defi cits, which may lead to diffi culties in reading and in other neuropsychological functions serves as a basis for the multiple defi cit model of dyslexia, which proposes a multivaried continuous performance characterized by cognitive abilities relating to reading (Menghini et al, 2010;Pennington, 2006;Pennington et al, 2012). These theories post that individual differences found in reading and writing are conceptualized in terms of a multidimensional model, where there is a continuous variation of language components and literacy abilities (Bishop & Snowling, 2002).…”

Literacy skill development of children with familial risk for dyslexia through grades 2, 3, and 8.

“…Several candidate susceptibility genes have been found to be linked to developmental dyslexia (Galaburda, LoTurco, Ramus, Fitch, & Rosen, 2006;Giraud & Ramus, 2012;Scerri & Schulte-Körne, 2010), and the idea of multiple risk factors, some of which are transmitted also to offspring without dyslexia, is widely accepted (Bishop, 2009;Pennington, 2006;Pennington & Lefly, 2001;Pennington et al, 2012;Snowling, 2008;Snowling et al, 2003). Pennington (2006) has suggested that multiple risk factors both in the genome and environments lead to a continuum of vulnerability instead of a dichotomous distribution of risk.…”