ERIC Number: EJ757949
Record Type: Journal
Publication Date: 2007-Feb
Reference Count: N/A
Etiology of Reading Difficulties as a Function of Gender and Severity
Hawke, Jesse L.; Wadsworth, Sally J.; Olson, Richard K.; DeFries, John C.
Reading and Writing: An Interdisciplinary Journal, v20 n1-2 p13-25 Feb 2007
To test the hypothesis that the etiology of reading difficulties may differ for males and females in more severely impaired samples, reading performance data from monozygotic (MZ), same-sex dizygotic (DZ[subscript ss]), and opposite-sex dizygotic (DZ[subscript os]) twin pairs were analyzed using a model-fitting implementation of the DeFries-Fulker (DF) model (Purcell & Sham, 2003, "Behavior genetics", 33, 271-278). Five non-independent samples were selected using cut-offs of -1 (N = 737 pairs), -1.5 (N = 654), -2 (N = 468), -2.5 (N = 335), and -3 (N = 198) standard deviations (s) below the mean composite reading score of control twins. Male/female gender ratios for children with reading difficulties were significantly higher than 1.0 for all five samples and increased as a function of severity (viz., 1.15, 1.17, 1.40, 1.61, and 1.88, respectively). When the DF model was fit to the data, estimates of heritability (h[subscript g [squared]] ) and shared environmental influences (c[subscript g [squared]] ) were not significantly different for males and females in any of the groups. Consequently, the most parsimonious model that provided a good fit to the data at all five levels of severity equated the heritabilities and shared environmental influences for males and females, and fixed the DZ[subscript os] coefficient of genetic relatedness at 0.5. Thus, these results provide no evidence for a differential etiology of reading difficulties as a function of gender in more severely impaired samples, and suggest that the same genetic and environmental influences contribute to reading difficulties in males and females, irrespective of severity.
Descriptors: Severity (of Disability), Environmental Influences, Etiology, Genetics, Twins, Reading Difficulties, Hypothesis Testing, Goodness of Fit
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Publication Type: Journal Articles; Reports - Descriptive
Education Level: N/A
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