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Although many tasks have been developed recently to study executive control in the preschool years, the constructs that underlie performance on these tasks are poorly understood. In particular, it is unclear whether executive control is comprised of multiple, separable cognitive abilities (e.g., inhibition and working memory) or whether it is unitary in nature. A sample of 243 normally developing children between 2.25 and 6 years of age completed a battery of ageappropriate executive control tasks. Confirmatory factor analysis (CFA) was used to compare multiple models of executive control empirically. A single-factor, general model was sufficient to account for the data. Furthermore, the fit of the unitary model was invariant across subgroups of children divided by socioeconomic status or sex. Girls displayed a higher level of latent executive control than boys, and children of higher and lower SES did not differ in level. In typically-developing preschool children, tasks conceptualized as indices of working memory and inhibitory control in fact measured a single cognitive ability, despite surface differences between task characteristics.Keywords: executive control, inhibition, working memory, preschool, confirmatory factor analysis Preschool Executive Control 3Using confirmatory factor analysis to understand executive control in preschool children:I. Latent structure Executive control is a term used to refer broadly to those cognitive abilities that are associated with, or subserved by, prefrontal cortex and interconnected subcortical system (Diamond, 2001;Stuss, 1992). Although research on executive control has been underway for several decades, remarkably there remains no well-agreed-upon definition as yet. One school of thought has conceptualized executive control as a group of relatively independent, or fractionated, cognitive abilities, typically including working memory, the ability to keep information in mind to guide ongoing or later behavior (Baddeley & Hitch, 1974); inhibitory control, the ability to keep irrelevant or misleading information from interfering with performance (Diamond, 1990;Harnishfeger & Bjorklund, 1993); and set-shifting, or adapting strategies to changing situational demands (Zelazo, Frye, & Rapus, 1996). In contrast, others have argued that executive control is a unitary, domain general construct that manifests in different ways depending on contextual demands (e.g., Duncan & Miller, 2002;Duncan & Owen, 2000).Prefrontal systems undergo a protracted course of development (Benes, 2001). In comparison with posterior cortical areas, the phases of prefrontal cortical development, including neuronal generation, differentiation, and synaptic pruning, occur later and over a longer period of time (Giedd et al., 1999;Huttenlocher, 1990). Myelination of fibers within prefrontal cortex is not complete until early adulthood (Paus et al., 2001). Executive control undergoes a similarly delayed developmental trajectory where, for example, performance on "classic" executive tasks like the T...

Although the structure of executive function (EF) in adulthood is characterized by both unity and diversity, recent evidence suggests that preschool EF may be best described by a single factor (Wiebe, Espy, & Charak, 2008). The latent structure of EF was examined in 228 3-year-olds using confirmatory factor analysis. Children completed a battery of executive tasks that differed in format and response requirements, and putative working memory and inhibitory control demands. Tasks appeared to be age appropriate, with adequate sensitivity across the range of performance and without floor or ceiling effects. Tests of the relative fit of several alternative models supported a single latent EF construct. Measurement invariance testing revealed less proficient EF in children at higher sociodemographic risk relative to those at lower risk, and no differences between boys and girls. At age 3 years, when EF skills are emerging, EF appears to be a unitary, more domain-general process.

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The development of response inhibition was investigated using a computerized go/no-go task, in a lagged sequential design where 376 preschool children were assessed repeatedly between 3.0 and 5.25 years of age. Growth curve modeling was used to examine change in performance and predictors of individual differences. The most pronounced change was observed between 3 and 3.75 years. Better working memory and general cognitive ability were related to more accurate performance at all ages, but relations with speed changed with age, where better cognitive skills were initially related to slower responding, but faster responding at later ages. Boys responded more quickly and were more accurate on go trials, whereas girls were better able to withhold responding on no-go trials.

Clinically diagnosed preschool children with ADHD showed robust inhibition deficits, whereas preschool children with DBD showed impaired inhibition especially where motivational incentives were prominent. Severity of inhibition impairment in the comorbid group was similar to the ADHD group.

Coincident with developments in the temporal-cortical explicit memory network, long-term recall abilities are newly emergent late in the first year of human life. We recorded event-related potentials (ERPs) in 9-month-olds as an index of the integrity of the neural substrate underlying a task thought to reflect explicit memory, namely, deferred imitation. ERP measures of recognition memory 1 week after unique laboratory experiences predicted whether and how much infants recalled of the experiences 1 month later. The findings further imply that memory storage and consolidation processes are a major source of variability in long-term recall memory late in the first year of life.