The Relationship Between Reading and Intelligence in Primary School Aged Children: Implications for Definitional Models of Dyslexia

The validity of definitional models of development dyslexia (DD) derived from the difference between intelligence and reading quotients, is challenged by the failure of these models to consider expected developmental changes in the relationship between these constructs. The purpose of this study was to examine age-related changes in the correlations between verbal and nonverbal intelligence and reading ability. One hundred and twenty six children aged between 7 11 years of age were administered the Peabody Picture Vocabulary Test Third Edition (PPVT-III, a measure of verbal intelligence) the Raven Coloured Progressive Matrices (CPM, as a measure of non-verbal intelligence) and various measures of reading ability (the Neale Analysis of Reading Ability Revised, NARA, and selected subtests from the Woodcock-Johnson Tests of AchievementRevised, WJ-Ach). The PPVT-III had significantly stronger correlations than the CPM with reading rate, single word reading, and a measure of text comprehension. Both measures correlated poorly with pseudo-word reading. Despite differences between the two intelligence measures, both correlated more strongly with measures of reading comprehension than with traditionally defined measures of decoding ability. These results are discussed in the context of the validity of current definitions of DD. The need for greater consideration of the appropriateness of certain assessment measures at various ages both in testing and in the interpretation of previous studies,