A Double-Deficit Hypothesis for Developmental Reading Disorders.

Two longitudinal studies examined a "double deficit" hypothesis of reading disorders that contends that along with a core phonological deficit, slow speed of lexical access disrupts the efficient formation of orthographic representations and their quick retrieval. In the first study, 38 children from 6 classrooms in a predominantly white, middle class public school, were tested repeatedly from early in grade 2 to the end of grade 4. Subjects were divided into groups (good decoder-fast reader, good decoder-slow reader, poor decoder-fast reader, and poor decoders-slow readers) based on grade 4 scores. Multiple analysis of variance examined effects of two levels of nonword decoding and word latency with time of test a repeated measure. Main effects of both factors and of time were observed on many measures, and few interactions of the factors occurred. In the second study, 82 children from 3 public schools representing a range of different socioeconomic levels were tested in the spring of every year on a battery of reading and language measures from kindergarten to grade 4. Children were divided into groups similar to those in the first experiment. Analyses similar to those in the first study were conducted. Results of both studies indicate that the two deficits have independent, additive effects. Findings suggest that the processes resulting in rapid reading reflect in large part a cognitive skill independent of phonological decoding, and that a double deficit conceptualization of reading disability is critical for a more comprehensive account of reading disabled children. (Twelve tables of data are included.) (RS)