A growing body of research indicates substantial comorbidity of Attention Deficit Hyperactivity Disorder (ADHD) and reading disabilities in children. As many as 50% of children with reading disabilities have symptoms of ADHD to varying degrees. However, the nature of the relation between ADHD and reading disabilities is not clear. For example, there is little evidence concerning how early the overlap is apparent. Research on reading has yielded a strong consensus that reading disabilities involve a phonological processing deficit, and that children's phonological processing skills can be measured prior to reading acquisition. Research on ADHD has implicated three sets of symptoms in the disorder: Inattention, Hyperactivity and Impulsivity. This study examined the relation between potential developmental precursors to ADHD (Hyperactivity and Impulsivity) and reading (phonological sensitivity) in a sample of preschool-aged children. As part of a larger longitudinal study, 65 preschool children (ages 2 to 4 years) were administered language, phonological sensitivity, and emergent literacy tests, and their parents completed the Emotionality, Activity, Sociability, and Impulsivity Temperament Scale (EASI; Bus & Plomin, 1975). Approximately 1-1/2 years following the initial assessment, children were again administered phonological sensitivity and emergent literacy tests.

Analyses revealed that one factor from the EASI, Impulsivity, was related to children's scores on the phonological and emergent literacy tests, and there was a trend for higher scores on the Activity factor of the EASI to be related to lower scores on these tests. In a series of multiple regression analyses, the Impulsivity factor was a unique predictor of children's scores, even when controlling for age, gender, and initial scores on language, phonological, and emergent literacy test. Higher levels of Impulsivity were associated with lower phonological and emergent literacy skills. This study needs to be replicated, and measures of inattention need to be examined for their relation to phonological sensitivity as well. The findings of this study, however, are consistent with research results with older children indicating high comorbidity of ADHD and reading disabilities, and they indicate that the connection might be present as early as the preschool period. These findings suggest that early identification may be possible, which may lead to preventative interventions.