The steady rising of IQ scores over the last century - known as the Flynn effect - causes IQ tests norms to become obsolete over time. To counter this effect, IQ tests are "renormed" (made harder) every 15-20 years by resetting the mean score to 100 to account for the previous gains in IQ scores. But according to new research, such renorming may have unintended consequences, particularly in the area of special education placements for children with borderline or mild mental retardation. The findings are reported on in the October issue of American Psychologist, a journal of the American Psychological Association (APA).
Researchers Tomoe Kanaya, M.A. and Stephen J. Ceci, Ph.D., of Cornell University and Matthew H. Scullin, Ph.D., of West Virginia University used IQ data from nearly 9,000 school psychologist special education assessments from nine school districts across the U.S. to document how the Flynn effect influences mental retardation diagnoses for several years after a new test is introduced.
The students (ages 6 - 17) were from different geographical regions, neighborhood types and socioeconomic status.
The results show that the test renorming due to the Flynn effect influences which children are diagnosed with mental retardation regardless of their actual cognitive ability. According to the researchers, children in the same classroom with the same cognitive ability could be diagnosed differently simply because different test norms were used for each child. Students in the borderline and mild mental retardation range lost an average of 5.6 IQ points when retested on a renormed test and were more likely to be classified mentally retarded compared with peers retested on the same test, according to the study.
Specifically, when a commonly used IQ test (the Wechsler Intelligence Scale for Children or WISC) was renormed to account for the Flynn effect, the...