The construct validity of the Tower of LondonDX as a measure of the executive functioning of ADHD children.

Currently, there are a limited number of measures that have been developed to assess childhood executive planning and problem-solving abilities. The present study represents ongoing efforts to determine the psychometric properties of the newly developed Tower of London Drexel (TOLDX), a measure of executive functions. Specifically, the construct-related validity of the TOLDX was investigated with a sample of attention-deficit hyperactivity disorder (ADHD) children (N = 129), 7 to 15 years of age. The performance of the children on a neuropsychological battery of measures sensitive to executive abilities, psychometric intelligence, and memory was subjected to maximum-likelihood factor analysis. A four-factor solution was extracted that best fit the selected variables. The TOLDX was found to produce the highest loading on an Executive Planning/Inhibition factor comprised of other executive measures. The Executive Planning/Inhibition measure was separate from factors of Executive Concept Formation/Flexibility, Psychometric Intelligence, and Memory. Moreover, the two executive factors were found to be correlated (r = .42) suggesting that each assesses, to varying degrees, related executive dimensions. The neuropsychological construct structure of the TOLDX is discussed in relationship with the temporal organization of behavior and frontal lobe functioning.