A 3-Year Comparison Study of WISC-R and WISC-III Iq Scores for a Sample of Special Education Students

Abstract

The purpose of this study was to compare the Wechsler scores for the same group of students after a 3-year interval. A sample of 84 regular and special education students were tested first on the WISC-R and then 3 years later on the WISC-III. Scores were broken up into five score subgroups from lowest to highest. More WISC-III scores appeared in lower IQ ranges, whereas fewer WISC-III scores appeared in higher IQ ranges. It was surmised that the WISC-III was more difficult at the higher IQ ranges and less difficult at the lower IQ ranges. WISC-III Performance scores displayed more (lower) differences between administrations, whereas the Verbal scores, which were higher, showed more variability. Researchers concluded that practicing psychologists might be more inclined to place students in classes for the educable mentally retarded (EMR) based on the effects of lower Performance Scale scores than on Full Scale IQs.

Does the Flynn Effect Affect IQ Scores of Students Classified as LD?

“…The differences were, however, substantially smaller than predicted using the FE [i.e., Full Scale IQ (FSIQ) score difference was only about 2 points rather than the 5.7 points expected using Flynn's earlier reports (Flynn, 1984)]. Graf and Hinton (1994) then divided the sample into five IQ score-range subgroups (e.g., IQ 76-90) for the Verbal IQ (VIQ), Performance IQ (PIQ), and FSIQ scores, respectively. Contrary to what one might predict given the FE, Graf and Hinton (1994) reported that WISC-III VIQ, PIQ, and FSIQ results were somewhat higher than the WISC-R for the two low IQ groups (60-75 and 76-90).…”

“…Over the years, several studies have reported a decrease in students' IQ scores between different revisions of popular intelligence tests such as the Wechsler batteries (e.g., Bolen, Aichinger, Hall, & Webster, 1995;Carlton & Sapp, 1997;Gaskill & Brantley, 1996;Graf & Hinton, 1994;Lynn & Hampson, 1986;Slate & Saarnio, 1995;Spitz, 1989;Thorndike, 1975;Vance, Maddux, Fuller, & Awadh, 1996). One explanation for the observed decline in scores with successive revisions of IQ tests is a phenomenon known as the "Flynn effect" (FE;Flynn, 1984Flynn, , 1987.…”

“…Most researchers report that the Full, Verbal, and Performance scores are moderately to highly stable, especially as measured by correlations, when students in the United States are tested twice with the same version of the WISC [e.g., WISC-Revised (WISC-R; Wechsler, 1974); Naglieri & Pfeiffer, 1983;Oakman & Wilson, 1988;Truscott, Narrett, & Smith, 1994;or WISC-Third Edition (WISC-III;Wechsler, 1991); Canivez & Watkins, 1998]. Studies that compared scores for students tested with the two different versions of the Wechsler scales (WISC-R and WISC-III) have shown drops in IQ scores of 5-8 points (e.g., Bolen et al, 1995;Carlton & Sapp, 1997;Gaskill & Brantley, 1996;Graf & Hinton, 1994;Slate & Saarnio, 1995). This drop corresponds to what might be expected, given the FE, because the two tests were normed approximately 2 decades apart (WISC-R normed in approximately 1972; WISC-III normed in approximately 1989).…”

“…Only two published research studies were identified that specifically examined the FE with exceptional populations (Graf & Hinton, 1994;Spitz, 1989). These studies did not specifically single out students classified as LD.…”

“…Flynn (1985) disputed these results, and suggested that the differences seen in Spitz's study were attributable to norming differences between the WISC and WISC-R, but the dispute has not been resolved by replication. Graf and Hinton (1994) examined triennial data for 84 special education children tested first with the WISC-R and then with the WISC-III. Overall, they found small but significant decreases between the WISC-R and WISC-III Performance and Full Scale scores, but not for the Verbal Scale.…”