Test-retest IQ changes of epilepsy patients: assessing the influence of practice effects.

A number of recent studies have emphasized the role of practice effect on test-retest changes in performance often seen on neuropsychological tests. An attempt is made to separate the influence of practice effect from other functional changes in the test-retest differences observed on the WAIS for a sample of adult epilepsy patients. Fifty-eight epilepsy patients were divided into three groups based on their WAIS test-retest score changes. Their corresponding test-retest performance on the Halstead-Reitan Battery and changes in seizure frequency were compared and analyzed. Results indicated that there was a correspondence between improvement in neuropsychological test performance, reduced seizure frequency, and improvement on the WAIS. It was concluded that test-retest changes in neuropsychological test performance reflected changes in psychological functioning of these individuals rather than the influence of practice effect. Some general issues relating to the question of disentangling the influence of practice effect from other functional changes in status were raised and discussed.