Psychology in fhe Schooh Volume IS, October 1988

SIMILARITY OF WISC-R AND WAIS-R SCORES AT AGE 16

JONATHAN SANDOVAL, JULIUS SASSENRATH, AND MANUEL PENALOZA University of California, Davis

Thirty learning disabled students of average intellectual ability between 16 and 17 years of age were given both the WISC-R and the WAISR to determine if the WAIS-R provided higher average IQ scores, as had been reported for educationally mentally retarded adolescents. The results indicated: (a) no significant differences between the two scales on either the Verbal, Performance, or Full Scale IQs, (b) significant cor- relations between the WISC-R and WAIS-R on the three IQ scores and 9 of the 11 subtests, and (c) the emergence of the ACID profile for learning disabled adolescents on both tests.

The several Wechsler scales are the most widely used tools for making decisions in the schools about intellectual functioning (Bersoff, 1981; Goldstein, Arkell, Ashcroft, Hurley, & Lilly, 1975; Nagle & Lazarus, 1979). In addition to their good validity, high reliabilities, and excellent standardization, the Wechsler tests cover a wide age range from 7 to 74 years, with some overlap in ages between the different scales.

In discussing the age 16-17 overlap between the Wechsler Intelligence Scale for Children-Revised (WISC-R) and the Wechsler Adult Intelligence Scale-Revised (WAIS-R), Wechsler (1974, p.53) has suggested that the examiner is free to choose the scale that is most appropriate for hidher purposes. Choosing the appropriate scale, however, is not a clear-cut decision, as there appears to be a lack of similarity of scores from Wechsler’s children’s scales (WISC and WISC-R) to those from his adult scales (WAIS and WAIS-R).

Earlier, special education teachers reported that, although the WISC adequately estimated the intellectual potential of EMR children, the WAIS overestimated the children’s potential (Hannon & Kicklighter, 1970). Similarly, psychologists and other professionals have reported the WAIS to yield higher scores when retarded children are given both the WAIS and the WISC (Walker & Walker, 1972). Although Ross and Morledge (1 967) did not find significant differences between the WISC and WAIS in a normal population, several studies have revealed Full Scale IQ differences ranging up to 10 points higher for the WAIS than for the WISC with EMR populations (Covin, 1977; Walker & Gross, 1970; Walker & Walker, 1972; Wesner, 1973).

The findings of earlier studies on the WAIS and WISC-R (Craft & Kronenberger, 1979; Hannon & Kicklighter, 1970; Nagel & Lazarus, 1979; Wechsler, 1974) have been corroborated by the recent research of Zimmerman (1979, 1981). Zimmerman (1979) studied 25 EMR children, ranging from 12 to 16 years of age, with an average age of 15-8. She gave the students the WISC-R and retested them 19 months later on the WAIS. The results indicated that, on the average, the WAIS FSIQ exceeded the WISC-R FSIQ by 14 points. Similar results were found in another study by the same author (Zimmer- man, 1981). Using a sample of both learning disabled and educable mentally retarded children between the ages of 12 and 16, with an average age of 14-1, Zimmerman retested the children on the WAIS four years after initially testing them on the WISC-R. Cor- relation with the WISC-R FSIQ was high (r= .W), and the average WAIS FSIQ was found to exceed the mean WISC-R FSIQ by 11 points.

Send reprint requests to Jonathan Sandoval, Dept. of Education, University of California-Davis. Davis, CA 95616.

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374 Jonathan Sandoval, Julius Sassenrath, and Manuel Penaloza

Zimmerman (1982) and Nagle and Lazarus (1979) attributed this discrepancy in favor of the WAIS to differences in the standardization samples of the two assessment instruments. This view is consonant with that of Wechsler (1974). He believed that the discrepancies reflect real differences between the adolescents tested in the early 1950s for the WAIS standardization and those tested in the early 1970s for the WISC-R stan- dardization. Today’s 16-year-olds apparently perform better on WAIS tasks than did their counterparts 20 years ago.

A current review of the literature reveals only two unpublished studies and two published studies comparing the WISC-R and the WAIS-R using adolescents (Egolf, 1983; Rubin, Goldman, & Rosenfeld, 1985; Sattler, Polifka, Polifka, & Hilsen, 1984; Zimmerman, 1982), but 15 studies comparing the WAIS with the WAIS-R with various age groups (Ryan, Nowak, & Geisser, 1987). The meta-analysis of these latter 15 studies found that the WAIS-R yielded IQs approximately 6.5 points lower than those earned on the WAIS for normal and disordered individuals (Ryan et al., 1987).

Using a group of 80 16-year-olds from the standardization samples, Wechsler (1981) found correlations of .89 VIQ, .76 PIQ, and .88 FSIQ between the WISC-R and WAIS-R, with the WISC-R means only one or two points higher where differences ex- isted. Both Egolf (1983) and Rubin, Goldman, and Rosenfeld (1985) studied popula- tions of retarded individuals. In the Egolf study of 16-year-olds, he found the mean WAIS-R VIQ and FSIQ scores to be significantly higher than the WISC-R scores. In a group of residential mentally handicapped adolescents, Rubin et al. found a signifi- cant mean difference, with the WAIS-R being 11 points higher than the WISC-R. However, the differences were greater for those adolescents classified trainable than for those classified educable.

In mixed groups of mentally retarded and learning disabled students, Sattler et al. (1984) found no differences over four years time in the two tests for 30 18-year-old adolescents, but Zimmerman (1982) found that the WAIS-R IQs exceed those origin- ally obtained four years earlier on the WISC-R by an average of six points for 25 16-year-olds.

Although few adolescents between 16 and 17 years of age are referred for programs for exceptional children, such IQ differences can have important implications in the diagnosis, classification, and placement of children. The WAIS-R norms appear to generate higher scores, but the WISC-R results may provide more meaningful informa- tion, since the score usually will be based on a larger sample of items, particularly for low-functioning individuals. If the WAIS-R does yield higher scores, youngsters who formerly would have scored in the Mentally Deficient range on the WISC-R and have been eligible for services might conceivably score at the Borderline level on the WAIS-R; children classified as Superior on the WISC-R might be classified as Very Superior on the WAIS-R and thus be eligible for special programs for the gifted.

Extrapolating further, discrepancies between ability and achievement in children referred for a possible specific learning disorder will tend to be smaller when the WAIS-R is used instead of the WISC-R. Thus, decisions regarding assessment of learning disabilities, eligibility, and educational placement may be quite different depending on the instrument chosen (Swerdlik, 1977). It is apparent that the mere choice of the WISC-R vs. the WAIS-R for inclusion in a multitest battery will have the potential of affecting diagnostic or placement decisions that are reached by multidisciplinary teams.

Similarity of WISC-R and WAIS-R 375

Comparisons of the WISC-R and WAIS-R at different ability levels are exceed- ingly important, because the available research indicates that intertest score differences may vary with the intellectual level of the child. Zimmerman’s and Sattler et al.’s studies are the only ones to date that compare learning disabled children on both the WISC-R and WAIS-R. However, their studies used both EMR and LD children combined, thereby confounding the effects of ability level on intertest differences. The present study was designed to determine the comparability of the WISC-R and the WAIS-R among 16-year- old children who are learning disabled only and presumably of average intellectual ability.

METHOD Participants

The participants were 15 male and 15 female students between the ages of 16-0 and 16-11 years of age, with a racial composition of 18 Caucasians and 12 Hispanics. All adolescents were chosen from public school special education programs in the Sacra- mento, California area. The Full Scale IQs ranged from 87 to 116, and each youth was currently enrolled in a special education program for the learning disabled. Procedure

The tests were administered by an experienced examiner. The 11 WAIS-R subtests and the corresponding 1 1 WISC-R subtests (including the supplemental Digit Span subtest) were administered to each participant. The order of test administration was counterbalanced to control for practice effects. The participants were assigned randomly to one of the two test sequences, so that 15 participants received the WISC-R first, and the remaining 15 received the WAIS-R first. The average test-retest interval was 5 days.

RESULTS AND DISCUSSION The top of Table 1 presents the means, standard deviations, and mean differences

for the Verbal, Performance, and Full Scale IQs for both tests. A 2 x 2 (test by order of administration) repeated measures analysis of variance was applied to these data. There were no significant main effects between the Verbal IQs, F(1,29) = 1.03, p > .05, the Performance IQs, F(1, 29)=2.01, p>.O5, or the Full Scale IQs, F(1, 29)- 1.89, p> .05, for the two tests. Also there were no significant main effects for order between the two tests for Verbal IQs , F(1,29) = 1.79, p > .05, Performance IQs, F(1 , 29) = 2.79, p>.05, or Full Scale IQs, F(1, 29) = 1.99, p>.05. No significant interaction was found between test and order of administration, F(1, 29)= 1.17, p>.05.

Table 1 also presents the means, standard deviations, and mean differences for each WISC-R subtest and its WAIS-R counterpart. Five WISC-R subtest means were significantly higher than their corresponding WAIS-R subtest means: Information, t(29) =4.41, p < .05, Vocabulary, t(29) = 5.60, p< .05, Comprehension, t(29) = 9.56, p< .05, Picture Completion, t(29) = 2.83, p < .05, and Object Assembly, t(29) = 6.46, p < .05. For these multiple t-tests, the Bonferoni method was used to retain alpha at .05.

To assess more fully the comparability of the WISC-R and WAIS-R, Pearson product-moment correlation coefficients were computed between corresponding subtests and IQ scores. These correlations are shown in Table 2. As can be seen, the correlations for the subtest scaled scores ranged from .28 for Picture Completion to .93 for Vocabulary and Comprehension. Of the 1 1 correlations between subtests, nine reached

376 Jonathan Sandoval, Julius Sassenrath, and Manuel Penaloza

statistical significance. On the other hand, all three correlations between the WISC-R and WAIS-R Verbal IQs, (r= .96, p < .Ol), Performance IQs, (r= .82, p < . O l ) , and Full Scale IQs (r= .96, p < .01) were significant and high.

Table 1 Means, Standard Deviations, and Mean DLffeences on the WISC-R and WAIS-R

Subtest Mean WISC-R WAIS-R

x SD x SD Difference

Verbal IQ

Performance IQ Full Scale IQ Information Similarities Arithmetic Vocabulary Comprehension Digit Span Picture Completion Picture Arrangement Block Design Object Assembly Coding

89.80 104.60 96.45

8.30 8.31 6.90 8.70 9.70 6.90

12.40 10.60 10.90 12.70 7.30

15.94 8.42

10.86 2.60 3.31 2.10 3.52 2.64 1.97 1.60 2.14 1.68 1.66 2.25

90.61 101.80 95.35

6.80 7.90 7.10 6.90 7.50 7.35

10.45 10.00 10.30 10.90 7.00

13.66 10.71 12.20 1.80 2.49 1.55 2.67 2.84 1.81 1.67 3.16 2.11 1.62

1.41

.81 2.80 1.10 1.50* .40 .20

1 .SO* 2.20. .45

1.95. .60 .60

1 .SO* .30

*p< .os.

Table 2 Correlations Between Corresponding WAIS-R and WISC-R Subtest and IQ Scores

Subtest Scores 1 IQ Scores r

Information Similarities Arithmetic Vocabulary Comprehension Digit Span

Picture Completion Picture Arrangement Block Design Object Assembly Digit Symbol/Coding

.82** Verbal IQ .96**

.85** Peformance IQ .82**

.47** Full Scale IQ .96** ,931. .93** .72**

.28

.62**

.54**

.34

.72**

**p< .01.

Similarity of WISC-R and WAIS-R 377

The mean scaled scores for all the subtests were rank ordered from lowest to highest and submitted to a Spearman rho correlational analysis. The subtest rankings on the two instruments were significantly correlated (rs = .78, p < .05). On the WISC-R, Infor- mation, Coding, Arithmetic, and Digit Span ranked 4th, 3rd, 2nd, and lst, respectively, out of 11 subtests. On the WAIS-R, the corresponding subtests were ranked lst, 3rd, 4th, and 5th, respectively. Picture Arrangement, Block Design, Picture Completion, and Object Assembly were ranked 8th, 9th, loth, and 11th on both the WISC-R and

The present findings indicate that the WAIS-R did not produce significantly higher IQ scores for this group of learning disabled children with average ability in the 16-17-year age range. The mean differences were approximately one point for the Verbal and Full Scale IQs, and three points for the Performance IQs. The data indicate that the mean WAIS-R and WISC-R IQs are comparable, yielding equivalent Verbal, Performance, and Full Scale IQs.

The magnitude of the IQ differences in the present study is considerably smaller than that reported by Zimmerman (1982), using students whose intellectual functioning fell within the educable mentally retarded range. She reported that the WAIS-R IQs exceeded those on the WISC-R by an average of six points. The results of our study more closely parallel those reported by Wechsler (1981) comparing the WISC-R with the WAIS-R using normal, intellectually average 16-year-olds. He did not find differences in IQ scores.

It appears that the recently revised version of the WAIS, the WAIS-R, generates less discrepant IQ scores than did its predecessor, particularly within the average range of intellectual ability. The comparability of IQ scores may reflect improvements in the standardization samples of the WISC-R and the WAIS-R. The WISC standardization sample was tested just after World War 11, prior to the impact of television and mass media, and before the advent of kindergarten and nursery school education; in addi- tion, a larger percentage of youth now attend high school. The WISC-R standardiza- tion group, tested in the early 1970s, had the benefits of mass media, more enlightened and better educated parents, early childhood education, and a larger high school atten- dance, and hence greater cultural and educational advantages. The end result was a set of WISC-R norms that are higher than the WISC norms. Thus, when children of today are compared to their contemporaries, their scores will not be as high as they will be when they are compared to their less enriched age-counterparts of a generation ago (in the WISC sample).

A similar trend emerges in the comparison of the WAIS with its revised version, the WAIS-R. A study by Rabourn (1983) suggests that, like the revision of the WISC (WISC-R), the WAIS-R norms are higher than the WAIS norms. It appears that to score within the average range of IQ on the WAIS-R requires more ability than would be required on the WAIS. Thus, when given both instruments, today’s adults will score higher on the WAIS than they would on the WAIS-R.

Significant and very high correlations were found between the Verbal, Performance, and Full Scale IQs. Also, 9 of the 11 subtests had significant and moderately high cor- relations, indicating that the content of the corresponding subtests is similar for 16-year- olds. An analysis of the rankings in mean subtest scores also revealed a consistent pat- tern. On both instruments, Information and Arithmetic were among the most difficult

WAIS- R.

378 Jonathan Sandoval, Julius Sassenrath, and Manuel Penaloza

subtests, ranking within the top four. Scores on these two subtests seem to be characteristically depressed for a variety of populations of children with reading disorders (McManis, Figley, Richert & Fabre, 1978; Rugel, 1974) and with learning disabilities in general (Bryan & Bryan, 1975; Smith, Coleman, Dokeki, & Davis, 1977). Additionally, Digit Span and Coding were within the top three rankings on both scales. The characteristically low scores on this group of four subtests have been variously inter- preted along a distractibility (Kaufman, 1975) or sequencing (Bannatyne, 1974) dimension.

The ACID (Arithmetic, Coding, Information, and Digit Span subtests) profile, which is almost identical to the Bannatyne sequential category, clearly emerges on both instruments. These subtests were among the four most difficult subtests on the WISC-R and the five most difficult on the WAIS-R, suggesting that the WISC-R and the WAIS-R reflect similar ACID profiles for children with learning disabilities.

The lowest ranked subtests on both instruments were identical. Object Assembly had the lowest ranking, followed by Picture Completion, Block Design, and Picture Arrangement. This ranking is consistent with the observations of Kaufman (1979), who found that learning disabled children, as a group, tend to score highest on the WISC-R Object Assembly and Picture Completion subtests. The fourth rank of Picture Com- pletion is consistent with the third rank in the seven studies summarized by Lutey (1977) and in the two WISC-R investigations not included in Lutey’s review (Smith et al., 1977; Zingale & Smith, 1978).

The present results document the similarity between the WISC-R and the WAIS-R for 16-year-olds who are learning disabled and have average intellectual ability. Future research will need to evaluate the predictive validity of both instruments on such measures as school achievement, adaptive behavior, and vocational success and adjustment. Ad- ditional evidence is required to determine the comparability of the WISC-R and the WAIS-R for exceptional children of above average intellectual ability (gifted children).

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