In contrast, some researchers hold that a single factor (g) accounts for most of the variance in cognitive test performance. This view is supported by examination of the impact of different patterns of brain pathology on test performance. For example, Milberg and associates describe a number of distinct processes that might limit performance on single subtests of the Wechsler Adult Intelligence Scales- revised (WAIS-R). One view of the determinants of performance on standardized cognitive tests holds that performance is potentially the result of multiple factors. These results support the view that performance on any given cognitive test is potentially the result of multiple factors. More consideration should be given to models that include multiple uncorrelated latent factors as determinants of the performance on a given subtest. There appears to be a trade-off in modeling subtests as one dimensional and modeling with homogeneous latent traits. Overall these results show that models that describe subtests as multidimensional functions of uncorrelated factors provided a better fit to the WAIS-IV correlations than models that describe subtests as one dimensional functions of correlated factors. These multidimensional models also generalized well to new samples of populations differing in age from that used to estimate the model parameters. Multidimensional models of subtest performance provided better model fit as compared to several previously proposed one dimensional models. The present study used structural equation modeling to evaluate several multidimensional models of the Wechsler Adult Intelligence Scales- fourth edition (WAIS-IV) subtests. As a result, the simple structure of subtest performance results in complex latent factors. However these latent factors are not independent as they are related through hierarchical or oblique structures. Several latent factors are then used to model groups of subtests. Individual subtests in batteries designed to measure human abilities are commonly modeled as a single latent factor. Performance on a cognitive test can be viewed either as measuring a unitary function or as reflecting the operation of multiple factors.
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