Subtypes of learning disabilities in adolescents and adults

This study tested the hypothesis that a classification scheme developed for the subtyping of learning disabilities in children, when applied to a population of adolescents and adults, would result in subtyping into discrete and relatively homogeneous groups in terms of cognitive functioning and achievement. We compared three groups, arithmetic disability (AD), reading disability (RD), and reading and arithmetic disabilities (RAD), among themselves and with a comparison group with normal achievement (NA) on a variety of cognitive and achievement measures. The main findings were as follows: (a) Each of the groups differed significantly from the others on tests of reading, spelling, memory, and other cognitive measures; (b) both the RD and RAD groups showed a deficit in phonological processing, vocabulary, spelling, and STM; (c) the AD group performed similarly to the NA group on pseudoword reading and phonological processing, but did more poorly than the NA group on word reading and vocabulary; (d) on many tasks the RAD group performed more poorly than the other groups; and (e) the AD and RAD groups performed more poorly than the NA and RD groups on a visual-spatial task. This study demonstrated the validity of this classification scheme for the subtyping of learning disabilities in adolescents and adults.