An examination of the effects of age on repeated administration of a neuropsychological assessment battery

The assessment of higher cognitive functions using neuropsychological assessment instruments is receiving an increasing amount of attention within the fields of psychology and medicine. As the field has developed it has become necessary to understand the effects of different moderator variables on neuropsychological test performance in both normal and brain-damaged populations. The literature demonstrates a consistent age effect on test performance, particularly on measures which tap abilities which are fluid in nature. A practice effect has also been demonstrated on measures of fluid abilities when these tests are readministered to normal subjects. Tests which appear to measure crystallized intelligence are relatively resistant to the effects of age and practice. The present study was designed to take the research into test moderator variables one step further by examining the effect age has not only on the initial level of performance, but on the change in performance which is observed across administrations of the same instruments. The present study will hypothesize that older subjects will demonstrate a larger improvement in performance than younger subjects. A group of normal subjects and recovering alcoholic subjects will be compared.

The normal and alcoholic subjects were administered the same comprehensi7e battery of neuropsychological tests. The Trails B and the sum of WAIS-R Verbal Subtest Scaled scores were selected as representative measures of fluid and crystallized intelligence, respectively. The normal subjects were tested on 2 occasions with a test-retest interval of 3 months. The alcoholics were tested while in a residential treatment program and reassessed after a 3 week test-retest interval. The hypotheses were evaluated using a simple analysis of variance and repeated measures analysis of variance.

The data did not support the hypothesis that older subjects would perform Trails B slower than younger subjects, but did support the hypothesis that the WAIS-R results would not differ. A practice effect was demonstrated on both the Trails B and the WAISR. An age by practice interaction was not demonstrated even when the groups were combined. An analysis of covariance was performed to control for the effects of the different test-retest intervals, but there remained no significant interaction of age with practice.