Utilising the WAIS-III/WMS-III in clinical practice: Update of research and issues relevant to Australian normative research

Metric and structural equivalence of core cognitive abilities measured with the Wechsler Adult Intelligence Scale-III in the United States and Australia

Equivalence of the psychological model underlying Wechsler Adult Intelligence Scale-Third Edition (WAIS-III) scores obtained in the United States and Australia was examined in this study. Examination of metric invariance involves testing the hypothesis that all components of the measurement model relating observed scores to latent variables are numerically equal in different samples. The assumption of metric invariance is necessary for interpretation of scores derived from research studies that seek to generalize patterns of convergent and divergent validity and patterns of deficit or disability. An Australian community volunteer sample was compared to the US standardization data. A pattern of strict metric invariance was observed across samples. In addition, when the effects of different demographic characteristics of the US and Australian samples were included, structural parameters reflecting values of the latent cognitive variables were found not to differ. These results provide important evidence for the equivalence of measurement of core cognitive abilities with the WAIS-III and suggest that latent cognitive abilities in the US and Australia do not differ.

Does Effort Suppress Cognition After Traumatic Brain Injury? A Re-Examination of the Evidence for the Word Memory Test

Green, Rohling, Lees-Haley, and Allen (2001) suggested that scores on a test of "effort," the Word Memory Test (WMT), explains more variance in outcome after brain injury than does injury severity. As a consequence, Green and colleagues recommend using the WMT to control for sub-optimal effort in neuropsychological evaluations and group research. We re-examine the evidence for their conclusions and argue that identifying a larger proportion of explained variance is not in itself evidence of validity unless the premise to be proven is already assumed, namely, that the test is a valid measure of effort. Instead, the crux of Green and colleagues claim for the validity of the WMT implies an interaction between effort and injury severity on outcome scores, although the specific interaction has not been tested in their previous research. We failed to find any evidence for this interaction in a sample of 100 Australian litigants. We conclude that our data do not support the view that effort, as measured by the WMT, interacts with injury severity to suppress cognition after brain injury.