A Comparison of WAIS-R and WAIS-III in the Lower IQ Range: Implications for Learning Disability Diagnosis

Background Whether the Flynn effect (the increase in the populations’ IQ over time) affects the IQ scores of people with learning disability or borderline learning disability remains unclear. The issue is important as the Flynn effect should alter the number of people eligible for health service resources. A comparison of the Wechsler Adult Intelligence Scale-Revised (WAIS-R) with the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III) in individuals with learning disability or borderline learning disability was conducted. Method All participants completed the WAIS-R and the WAIS-III. Discrepancy scores were calculated for the Full Scale IQ score and the Verbal and Performance subscale scores. Results WAIS-III Full Scale scores were significantly lower by over 4 IQ points. Verbal and Performance Scale IQ scores were also significantly lower than the corresponding WAIS-R scores. Conclusion The shift from WAIS-R to WAIS-III means that 66% more people meet criterion A for the diagnosis of learning disability and hence this has major resource implications for health service providers.