Is it true that the differences in reading performance between students with and without LD cannot be explained by IQ?

This study was designed to demonstrate whether the differences in reading between students with learning disabilities (LD) and non-learning disabled students (NLD) can be explained by IQ. A sample of 133 Spanish children (85 male, 48 female) ranging in age from 8 to 13 years were classified into four groups according to IQ as measured by the Wechsler Intelligence Scale for Children-Revised (< 80; 81-90; 91-109: 110-140) and into two groups based on reading level (LD and NLD). A lexical decision task was used and we manipulated different word parameters (length, positional syllabic frequency, and familiarity) and pseudoword parameters (length and positional syllabic frequency) to study the routes used by both groups. Our findings indicate that IQ does not explain the differences between children with LD and NLD children in lexical processing. We found that the lexical and sublexical parameters have a greater influence on students with LD than NLD students, independent of IQ. In synthesis, the LD group has more difficulty in lexical processing, which is influenced by poor phonological skills.