Familial patterns of learning disabilities

Male vulnerability to reading disability is not likely to be a myth: a call for new data

Whether boys are more vulnerable than girls to reading disabilities (RD) is controversial. We review studies that were designed to minimize ascertainment bias in the selection of individuals with RD. These include population-based studies that identified children with RD by objective, unbiased methods and studies that examined the gender ratios among the affected relatives of those diagnosed with RD. We conclude that even when ascertainment biases are minimized, there is still a significant preponderance of boys with RD, although the gender ratio of the affected relatives of those with RD manifests the weakest male bias. Furthermore, we demonstrate that potentially confounding factors such as attentional or neurological problems, race, IQ, and severity of RD cannot account for the observed gender bias. We end with a clarion call to future researchers to (a) consider analyzing gender differences by means of more than one definition of RD, (b) compare gender ratios when boys and girls are ranked against the performance of their own gender as opposed to an average across genders, and (c) report group differences in variability and effect sizes of obtained gender ratios.

The familial incidence of symptoms of scotopic sensitivity/Irlen syndrome: comparison of referred and mass-screened groups

The familial incidence of Scotopic Sensitivity/Irlen Syndrome was investigated in two samples. One sample involved parents and siblings of 126 children identified with symptoms who had been referred for screening. The other sample involved parents and siblings of 33 children who had been identified with symptoms through mass screening of all children in Grades 3 to 6 at two local schools. Two different samples were taken to investigate the possibility of parental referral bias. Familial incidence may be inflated in a referred sample because some parents may be aware of their own symptoms and actively seek assistance. For the sample of children referred for screening, there was an 81% chance of either one or both parents showing similar symptoms and a 76% chance of siblings being similarly affected. For the sample of children identified through school screening, there was an 85%, chance of either one or both parents showing similar symptoms and a 54% chance of siblings being similarly affected. The data confirm previous estimates of incidence and suggest that Scotopic Sensitivity/Irlen Syndrome may be a genetically-based deficit in visual processing.

The familial incidence of symptoms of Scotopic Sensitivity/Irlen syndrome

The familial incidence of Scotopic Sensitivity/Irlen Syndrome was investigated using parents of 751 children identified with symptoms. Children were identified by methods independent of their parents' symptoms or lack of symptoms. For these children, there was an 84% chance of either one or both parents showing similar symptoms, with similar numbers of mothers identified with symptoms as fathers. The data suggest that Scotopic Sensitivity/Irlen Syndrome may be a genetically based deficit in visual processing, but the simplest genetic models do not appear to fit.