Cerebellar tests differentiate between groups of poor readers with and without IQ discrepancy

A comprehensive test battery, including phonological, speed, motor and cere bellar tasks, was administered to the entire cohort of two schools for chil dren with learning disabilities. Testing was undertaken blind without acces sing the psychometric data on the children. Children were then allocated to a discrepancy group on the basis of their IQ, with the majority (n = 29) c lassified as nondiscrepant (IQ < 90) and a smaller set (n = 7), with IQ of at least 90, classified as discrepant (with dyslexia). Both groups showed s ignificant deficits relative to age-matched controls on almost all the test s. On phonological, speed, and motor tasks, the nondiscrepant group were at least as severely impaired as the discrepant group. By contrast, on the ce rebellar tests of postural stability and muscle tone, the nondiscrepant gro up performed significantly better than the children with dyslexia and close to the level of the controls. The findings indicate that cerebellar tests may prove a valuable method of differentiating between poor readers with an d without IQ discrepancy. The findings are interpreted in terms of the cere bellar deficit hypothesis for dyslexia.