Practice effects on the WAIS-III across 3- and 6-month intervals

Fifty-one participants (age M = 24.6; education M = 14.4 years) were administered the Wechsler Adult Intelligence Scale - Third Edition (WAIS-III) at baseline and at an interval of either 3 or 6 months later. Full Scale IQ (FSIQ), Verbal IQ (VIQ), Performance IQ (PIQ), Verbal Comprehension Index (VCI), Perceptual Organization Index (POI), and Processing Speed Index (PSI) scores improved significantly across time, whereas no significant change occurred on the Working Memory Index. Specifically, test scores increased approximately 3, 11, 6, 4, 8, and 7 points, respectively on the VIQ, PIQ, FSIQ, VCI, POI, and PSI for both groups. Notably, the degree of improvement was similar regardless of whether the inter-test interval was 3 or 6 months. These findings suggest that prior exposure to the WAIS-III yields considerable increases in test scores. Reliable change indices indicated that large confidence intervals might be expected. As such, users of the WAIS-III should interpret reevaluations across these intervals cautiously.