Unitary Deficit Hypotheses of Reading Disabilities: Has Vellutino Led Us Astray?

Abstract

The present paper evaluated the empirical and theoretical basis upon which several recent studies rejected the hypothesis of a visual-perceptual deficit in reading disabilities. It was shown that because of problems with task definition and test ceilings, the studies failed to provide a convincing refutation of this hypothesis. Similar problems were cited for the alternative verbal-mediational deficit hypothesis offered by the studies. An attempt was also made to show some of the problems with unitary deficit hypotheses by illustrating the importance of developmental factors, one source of complexity, for interpreting the performance correlates of reading disabilities.