Abstract
Working memory (WM) and inhibitory control (IC) are considered related but separable executive functions (EFs) among adults and adolescents. Although available evidence suggests that these constructs have not diverged especially among younger preschool children, questions remain regarding the age at which separable factors emerge. This study used confirmatory factor analysis to test a 2-factor model of EF among 289 preschool children whose ages ranged from 45 to 63 months (M = 55.74, SD = 7.56). As hypothesized, the model including separate but related factors provided a significantly better fit than a unitary model, indicating the presence of distinct WM and IC factors. Based on evidence that WM and IC measured during preschool relate differently to a variety of academic and behavioral outcomes, it was hypothesized that a model including separate factors for each EF would fit the observed data better than a single-factor model. Although the two-factor model provided the best fit for the full sample, the correlation between WM and IC factors was significantly higher for younger (ϕ =.95) than older (ϕ =.68) children, indicating increasing divergence as a function of age.