Language Phenotype for Reading and Writing Disability: A Family Approach

A theory-driven battery of 23 psychometric measures of reading, writing, and related language processes was administered to 102 probands (affected children in Grades 1 to 6 with documented reading problems, writing problems, or both) and both of their biological parents. Affected children and parents were compared on the structural relationships between related language processes (Verbal IQ VIQ, orthographic, phonological, and rapid naming skills), component reading, (accuracy, rate, comprehension) and writing (handwriting, spelling, composition) skills. The orthographic factor had significant paths to all reading and writing skills, except reading comprehension, in both probands and adults. The phonological factor had significant paths to all reading and writing skills except reading rate and handwriting in probands, but in affected adults only if VIQ was removed. Rapid naming had significant paths only to reading rate in probands and adults. VIQ had significant paths to reading comprehension in probands and adults, and to reading accuracy, reading rate, spelling, and composition in affected adults, but not probands. These results are consistent with the claim of functional systems theory that the same language processes are orchestrated flexibly depending on task at hand. Results for across-age differences in the covariances among related language processes confirmed developmental predictions of connectionist theory. The number of language deficits (based on discrepancy from VIQ) uniquely predicted severity of reading and writing problems in children and spelling problems in adults.