Differential aspects of conceptual processing in the Category Test and Wisconsin Card Sorting Test.

Ninety-six veterans from neuropsychiatric wards were administered the Category Test (CT), Wisconsin Card Sorting Test (WCST), and a series of concept formation tests assessing attribute identification and rule learning. The CT and WCST shared only 30% common variance, and related to different facets of concept formation. The WCST was associated with attribute identification, which entails discrimination of relevant features, while the CT was more related to rule learning, which assesses the deduction of classification rules. The CT and WCST should not be regarded as similar measures of one construct such as "abstraction." Use of discrete scores from each test can help assess different aspects of concept formation.