The Factorial Structure of the Tower Test from the Delis-Kaplan Executive Function System: A Confirmatory Factor Analysis Study.

The Tower of London (TOL) is a well-known, widely used task that captures executive function abilities. We examined the factorial structure and discriminant validity of three measures extracted from the Delis-Kaplan Executive Function System (D-KEFS) version of the TOL, namely the D-KEFS Tower Test, in 270 individuals from a publicly available release of the Enhanced Nathan Kline Institute-Rockland sample. Confirmatory factor analyses revealed a multidimensional three-factor solution of the measures extracted from the D-KEFS Tower Test; first-move-time, excess moves, and rule violations. This model was better than the unidimensional model, the two-factor model, the bifactor model and the model that included the total achievement scores. These results support the discriminant validity of the three latent factors, over their distinct relations to the total achievement score. The best fitting model was gender-invariant and age-variant. Overall, the multidimensionality of the measures extracted from the D-KEFS Tower Test reflects the need to use multiple metrics from this version of TOL to capture executive functions instead of a single score.