Why children with ADHD do not have low IQs

The major cognitive deficit of children with attention-deficit/hyperactivity disorder (ADHD) is impaired executive function (EF), a cognitive component that some theorists believe to be the primary substrate for the general intelligence (g) factor. We review the constructs of g and EF and the relevant research findings on ADHD. We then analyze the results of a battery of diverse tests, including measures of EF, administered to 123 boys with ADHD. The correlations among the EF measures, two well-accepted measures of IQ, and the g factor extracted from the entire battery are trivial at best. These results are discussed in the context of collateral evidence supporting the independence of g and EF and its clinical and theoretical implications.