The unity and diversity of executive functions and their contributions to complex "Frontal Lobe" tasks: a latent variable analysis

This individual differences study examined the separability of three often postulated executive functions-mental set shifting ("Shifting"), information updating and monitoring ("Updating"), and inhibition of prepotent responses ("Inhibition")-and their roles in complex "frontal lobe" or "executive" tasks. One hundred thirty-seven college students performed a set of relatively simple experimental tasks that are considered to predominantly tap each target executive function as well as a set of frequently used executive tasks: the Wisconsin Card Sorting Test (WCST), Tower of Hanoi (TOH), random number generation (RNG), operation span, and dual tasking. Confirmatory factor analysis indicated that the three target executive functions are moderately correlated with one another, but are clearly separable. Moreover, structural equation modeling suggested that the three functions contribute differentially to performance on complex executive tasks. Specifically, WCST performance was related most strongly to Shifting, TOH to Inhibition, RNG to Inhibition and Updating, and operation span to Updating. Dual task performance was not related to any of the three target functions. These results suggest that it is important to recognize both the unity and diversity of executive functions and that latent variable analysis is a useful approach to studying the organization and roles of executive functions.     

Differential roles for visuospatial and verbal working memory in situation model construction

Two experiments investigated the processing of the spatial and causal dimensions of situation models. In Experiment 1, participants read texts varying in spatial and causal demands while responding to on-line spatial and causal probes. Experiment 2 used the same design, but used texts that more tightly integrated spatial and causal information. In both experiments, spatially oriented dependent measures were generally influenced by spatial, but not causal, demands, whereas causally oriented measures were influenced by causal, but not spatial, demands. In addition, spatially oriented dependent measures were generally correlated with a measure of spatial working memory capacity, whereas causally oriented measures were correlated with a measure of verbal working memory capacity. These results indicate that spatial and causal dimensions of situation models are maintained and elaborated independently in different working memory subsystems.     

Performance of expert abacus operators

Ten expert abacus operators were given various restrictions and distractions during addition of ten numbers of 3–5 figures. All subjects except one could calculate very rapidly without an abacus, probably relying upon its mental representation. Some of those at an intermediate level of mastery moved their fingers as if they had been manipulating a real abacus, and prohibition of this movement or interfering finger-tapping reduced their performance. All the subjects could answer simple non-mathematical questions during abacus calculation without increasing time or errors, but answering extraneous mathematical questions was very hard.