A Comparison of the Cognitive Deficits in Reading Disability and Attention-Deficit/Hyperactivity Disorder Author(s): Erik G. Willcutt Institute for Behavioral Genetics, University of Colorado at Boulder Bruce F. Pennington Department of Psychology, University of Denver Richard Boada Department of Psychology, University of Denver Jamie S. Ogline Department of Psychology, University of Denver Rachel A. Tunick Department of Psychology, University of Denver Nomita A. Chhabildas Department of Psychology, University of Denver Richard K. Olson Department of Psychology, University of Colorado at Boulder Source: Journal of Abnormal Psychology. Vol. 110 (1) February 2001, pp. 157-172. American Psychological Association ISSN: 0021843X Digital Object ID: 10.1037//0021-843X.110.1.157 Article Type: Journal Article Abstract: This study used a nonreferred sample of twins to contrast the performance of individuals with reading disability (RD; n = 93), attention-deficit/hyperactivity disorder (ADHD; n = 52), RD and ADHD (n = 48), and neither RD nor ADHD (n = 121) on measures of phoneme awareness (PA) and executive functioning (EF). Exploratory factor analysis of the EF measures yielded underlying factors of working memory, inhibition, and set shifting. Results revealed that ADHD was associated with inhibition deficits, whereas RD was associated with significant deficits on measures of PA and verbal working memory. The RD + ADHD group was most impaired on virtually all measures, providing evidence against the phenocopy hypothesis as an explanation for comorbidity between RD and ADHD. A Comparison of the Cognitive Deficits in Reading Disability and Attention-Deficit/Hyperactivity Disorder By: Erik G. Willcutt Institute for Behavioral Genetics, University of Colorado at Boulder Bruce F. Pennington Department of Psychology, University of Denver Richard Boada Department of Psychology, University of Denver Jamie S. Ogline Department of Psychology, University of Denver Rachel A. Tunick