The construct validity of the MCST was examined in 60 geriatric rehabilitation participants by examining how traditional frontal measures, IQ estimate and the Information subtest of the WAIS-R predicted each of the clinical scores generated by the MCST. Stepwise Forward Multiple Regressions were used finding significant (p<.05) predictions for six of the seven MCST scores, each accounting for between 25 and 50% of variance.
As seen in the figure below, both executive and intellectual measures are important in the predictions. The results suggest that the original PR (Perseverative Response) and CA (Categories Achieved) scores, as well as the new APR (Automatic Perseverative Response) and GF (Generative Fluency-ease with which the sorting principles are verbalized) scores, though sensitive to executive functioning, are also somewhat sensitive to global cognitive decline.
It could be argued from these data that the APR and RPR (Reinforced Perseverative Response-perseverative responses that were correct in the prior phase of the test) are more specific and sensitive indicators of executive functioning than the remaining scores. This is reflected in the greater ratio of executive/intellectual contribution to these scores. On the other hand, the greater contribution of posterior measures to PR may cause masking of dysexecutive functioning in someone of superior intelligence (cf Heck & Bryer, 1986).
Overall, the results of this study support the usefulness of the MCST as a measure of executive functioning. Particularly illuminating in the present results is the need in card sorting tasks to integrate posterior and anterior functioning in order to form, maintain, and switch a mental set. Thus, fractionated scores are useful to get at various processes such as global cognitive efficiency for identifying relevant conceptual attributes, motor programming to establish new response, behavioral flexibility to inhibit well-established response, and perceptual flexibility to view stimuli in novel ways.
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