Analyzes composition reading performance data from identical and fraternal twin pairs in order to test the hypothesis that genetic influences are more important as a cause of reading disability in girls than in boys. Provides little or no evidence for the hypothesis of greater genetic influence on reading difficulties in girls than in boys. (SC)

Examines the etiology of high reading ability in twin pairs. Suggests that reading ability and its cognitive correlates are on a continuous distribution, with both extremes of the distribution being similarly heritable. Supports the hypothesis that the same cognitive processes that are associated with dyslexia are important for the development of…

Examines the "sib pair" method of linkage analysis designed to locate genes influencing dyslexia, which has several advantages over the "LOD" score method. Notes that the sib pair analysis was able to detect the same linkages as the LOD method, plus a possible third region. Confirms that the sib pair method is an effective means of screening. (RS)

Investigates genetic influences on reading in a sample of 285, 13-year-old twins. Finds the heritability of disability for reading recognition to be nonsignificant but that spelling had a substantial genetic contribution to all levels of disability. Suggests two possible independent aspects of phonological ability, each influenced by genetic…

Applies an extension of an earlier multiple regression model for twin analysis to the problem of detecting linkage in a quantitative trait. Detects a number of possible linkages, indicating that the approach is effective. Discusses detecting genotype-environment interaction and the issue of power. (RS)

Finds that parent-offspring resemblance in families of reading-disabled probands does not differ substantially from that in families of controls; and correlations and regressions for monozygotic twins are greater than those for dizygotic twins, suggesting that individual differences in reading achievement are due in part to heritable influences.…

Fits spelling data from identical and fraternal twins to a basic multiple regression model. Finds that about 60% of the deficit of probands was due to heritable influences. Finds a nonsignificant sex difference. Suggests collaborative analyses of data from additional twin studies of reading disability to facilitate more rigorous tests. (RS)

Follows 46 unselected children with various sex chromosome abnormalities using intellectual, language, and achievement testing. Notes that, although most children were not mentally retarded, most received special education help. Finds support for the inference that learning disorders were genetically mediated in this group. (RS)