Differences between WISC-III and WISC-R IQs: A Preliminary Investigation

Abstract

Differences between WISC-III and WISC-R IQs of 257 children (1 18 with Specific Learning Disability, 79 with Mental Retardation, and 60 who were not classified as disabled) were examined. As anticipated, the WISC-III and WISC-R IQs were highly correlated, ranging from .84 for the Full Scale IQs to .80 for the Performance IQs. The WISC-III Full Scale, Verbal, and Performance IQs were 7.2, 5.8, and 7.5 points lower than corresponding WISC-R values. The size of the difference between WISC-III and WISC-R IQs was correlated significantly with WISC-R (r = .34) and WISC-III (r = -.23) IQs. Differences in the size of the IQ drop were in part a function of disability group membership: Students with learning disabilities differed in the likelihood of increases and decreases in IQs in comparison to students with mental retardation. Sex was unrelated to the size of the IQ drop. Amount and direction of change were predicted by subtest scores. Importantly, high Object Assembly and Coding scores were primary factors in predicting increases in IQ, and higher Vocabulary scores predicted decreases in IQ.

Quantitative Brain Magnetic Resonance Imaging in Girls With Attention-Deficit/Hyperactivity Disorder

“…To allow comparison with our previous studies of boys, WISC-III full-scale, vocabulary, and block design subscale scores were converted to WISC-R equivalents on the basis of published data. [24][25][26][27] Thirty-five patients (70%) had been previously treated with stimulants, as determined from parental reports. Measures of stimulant drug exposure were lifetime exposure (yes or no), current daily dose in methylphenidate hydrochloride equivalents at the time of scann i n g ( 1 m g o f a m p h e t a m i n e s u l f a t e = 2 m g o f methylphenidate hydrochloride), and estimated cumulative lifetime methylphenidate equivalent dose calculated from parental reports.…”

The Croydon Assessment of Learning Study: Prevalence and educational identification of mild mental retardation

“…Comparisons of the WISC‐III and the WISC‐R reveal that subjects usually receive higher scores on the older test. This difference is greatest at the extremes of the IQ range (Slate & Saarnio, 1995; Wechsler, 1992a), with cognitively disabled children showing differences of around 7–8 points (Bolen, Aichinger, Hall, & Webster, 1995; Lyon, 1995; Truscott & Frank, 2001). There may be particular problems in test norms for subjects with MR, as calibration samples rarely include sufficient numbers of low ability subjects to enable the lower tail of the distribution to be estimated with adequate precision.…”

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

“…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).…”