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...

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Recent theory and research suggests that weak central coherence, a specific perceptual-cognitive style, underlies the central disturbance in autism. This study sought to provide a test of the weak central coherence hypothesis. In addition, this study explored the relations between the weak central coherence hypothesis, theory of mind skills, and social-emotional functioning in a group of high functioning children with autism. Results revealed equivocal support for the weak central coherence hypothesis, but found moderate correlations between verbal weak central coherence and theory of mind measures. No significant findings were observed between weak central coherence measures and social-emotional functioning.

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The extremes of birth weight and preterm birth are known to result in a host of adverse outcomes, yet studies to date largely have used cross-sectional designs and variable-centered methods to understand long-term sequelae. Growth mixture modeling (GMM) that utilizes an integrated person-and variablecentered approach was applied to identify latent classes of achievement from a cohort of school-age children born at varying birth weights. GMM analyses revealed 2 latent achievement classes for calculation, problem-solving, and decoding abilities. The classes differed substantively and persistently in proficiency and in growth trajectories. Birth weight was a robust predictor of class membership for the 2 mathematics achievement outcomes and a marginal predictor of class membership for decoding. Neither visuospatial-motor skills nor environmental risk at study entry added to class prediction for any of the achievement skills. Among children born preterm, neonatal medical variables predicted class membership uniquely beyond birth weight. More generally, GMM is useful in revealing coherence in the developmental patterns of academic achievement in children of varying weight at birth and is well suited to investigations of sources of heterogeneity.

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