Pryrhology in the Schools Volume 2 / . Julv, I984

THE USE OF THE McCARTHY SCALES OF CHILDREN’S ABILITIES TO ASSESS

MODERATELY MENTALLY RETARDED CHILDREN’ LAURA BICKETT, JEANETTE REUTER, AND TERRY STANCIN

Ken2 Srare Clniversiry

The performance of a sample of moderately mentally retarded children on the McCarthy Scales of Children’s Abilities (MSCA) was investigated by comparing their obtained mental age (MA) scores with their Stanford-Binet MAS and Minnesota Child Development Inventory (MCDI) developmental ages (DAs). All three MA es- timates correlated significantly, and there were no significant differences among mean MAS. However, valid MSCA Index scores could not be obtained for these moderately retarded children, using the current normative tables. Therefore, the MSCA cannot be recommended for measuring the intellectual level of retarded children for educational classification purposes.

The McCarthy Scales of Children’s Abilities (MSCA) is an instrument designed to assess the cognitive and motor abilities of children aged 2% to 8% years. Standard scores (Indexes) are derived from each of six scales: General Cognitive, Verbal, Perceptual- Performance, Quantitative, Memory, and Motor (McCarthy, 1972). The General Cognitive Index (GCI) provides a measure of the general intellectual level of the child and has properties that are similar to conventional IQs (mean of 100, standard deviation of 16). The MSCA has been seen as more advantageous than conventional IQ tests, such as the Stanford-Binet, because of the provision of six scale Indexes purported to measure specific abilities, the inclusion of gross and fine motor tasks, the child-oriented contem- porary nature of its tasks, the length and sequencing of the individual tests, and an age- appropriate range that allows it to be used with both preschool and primary-grade children (Gerken, Hancock, & Wade, 1978; Kaufman & Kaufman, 1977; Phillips, Pacework, & Tindall, 1978). In addition, McCarthy felt the MSCA would be par- ticularly useful for assessing the abilities of mentally retarded children because of the in- clusion in the test of a number of tasks appropriate for very young children. However, despite its several assets and seeming appropriateness, the MSCA has proven difficult to use with mentally retarded children.

Four studies have investigated the performance of educable mentally retarded (EMR) children on the MSCA. Two of these studies compared the performance of EMR children on the MSCA to their performance on the Stanford-Binet and reported mean IQs 18 to 20 points greater than mean GCIs (Levenson & Zino, 1979; Naglieri & Harrison, 1979). Investigators in both studies were unable to table GCIs for many of their EMR subjects using the MSCA normative tables which present GCIs that extend slightly beyond 3 standard deviations in either direction from the mean (McCarthy, 1972) and therefore should be sufficient to describe the performance of most EMR children. In both studies, extrapolated GCIs were assigned according to a table con- structed by Harrison and Naglieri (1978). Even with a table of extrapolated GCIs ex- tending 4% standard deviations below the mean, Naglieri and Harrison (1979) found that the MSCA performance of six of their EMR subjects could not be described.

Requests for reprints should be sent to Jeanette Reuter, Dept. of Psychology, Kent State University, Kent, OH 44242.

’This study was supported by Department of Education Research Grant No. DED-GO08001794 to Dr. Jeanette Reuter. Views expressed herein do not necessarily represent those of the Department of Education.

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306 Use of the MSCA

Harrison, Kaufman, and Naglieri (1980) investigated the profiles of 40 EMR children on the MSCA and reported that their GCIs ranged from 27 to 76, with a mean of 5 1.6. In this study, it was also necessary to table extrapolated GCIs for some of the subjects. Mean Indexes for the other MSCA scales could not be computed because too many of the EMR children scored below 3 standard deviations from the mean of the scales and their performance could only be described as less than 22. The range and the mean for this sample’s GCIs is of interest in light of the fact that the children had been placed in special education programs on the basis of previous Stanford-Binet or WISC-R IQs between 55 and 69. If the GCIs had been taken as equivalent to IQs, most of the children would have been identified as too low functioning to be in an EMR classroom.

Naglieri (1980) reported, for a sample of 20 EMR children, a significant mean difference of 7 points between the MSCA GCI and the WISC-R Full Scale IQ, with the GCI lower than the IQ. The GCI and the IQ correlated .82,p<.01. When the GCI and the WISC-R IQ were converted to a common metric, the mean GCI remained lower than the mean IQ, but not significantly so. It can be inferred from the mean and standard deviation of the MSCA GCIs (mean=55.5, standard deviation= 18.0) for these children that it was necessary to assign some extrapolated GCIs.

These four studies call into serious question the validity and utility of the MSCA when used to assess the abilities of mildly mentally retarded children. The results of the studies suggest that, when a mentally retarded child is assessed with the MSCA, there may have to be reliance on an extrapolated GCI, and the assessment of strengths and weaknesses may be rendered impossible due to an undifferentiated, uninterpretable profile of scale Indexes. These research findings also suggest that, for some mentally retarded children, Indexes obtained on the MSCA may underestimate ability level com- pared to standard scores obtained on the WISC-R and the Stanford-Binet. The nor- mative samples of all of these tests contained few mentally retarded children; therefore, scores obtained by mentally retarded children on these tests cannot be considered precise estimates of ability level. However, standard score cutoff points have been established for classification and educational placement purposes on the basis of a child’s performance on standardized, individual intelligence tests such as the WISC-R and the Stanford- Binet, on the assumption that these tests measure similar abilities and yield scores that are interchangeable. Evidence is accumulating, however, which indicates that this assumption may not be tenable for the MSCA.

In the present study, the validity and utility of the MSCA when used to assess the abilities of a sample of moderately mentally retarded children were investigated. Of primary interest was whether these children would perform significantly lower on the MSCA than on two other measures of cognitive functioning, replicating the findings on the performance of EMR children on the MSCA. The extension of MSCA Indexes to only 3 standard deviations below the mean and the reports on the performance of EMR children on the MSCA would seem to preclude its use with moderately mentally retarded children. However, Kaufman and Kaufman (1977) have suggested the use of mental age (MA) scores when MSCA Indexes cannot be tabled for exceptional children, and they have provided tables that allow for the establishment of an MA score in each of the six scales of the MSCA, provided a child’s level of mental and motor ability falls within the 2% to 8Yz-year range. These MA scores should be especially appropriate for school-age moderately mentally retarded children. As Kaufman and Kaufman have noted, since the MSCA goes down to age 2’12, there is an adequate floor to test older moderately mentally retarded children. Two criterion measures were selected to compare with MSCA MAS as

Use of the MSCA 307

derived from the Kaufman and Kaufman tables: MAS from the Stanford-Binet (Form L- M, 1972) and developmental ages (DAs) derived from a mother-completed developmen- tal assessment instrument, the Minnesota Child Development Inventory (MCDI), (Ireton, 1974).

METHOD Subjects

The subjects were 21 moderately mentally retarded children selected from the primary classes of two public schools for mentally retarded children in Northeastern Ohio. They were selected according to the criterion that they fall within the moderate range of mental retardation as determined by previous standardized intelligence testing performed to place them in primary classes supported by the Ohio Board of Mental Retardation. Specifically, their IQs fell within the 36 to 51 range, and their MAS were within the 3- to 8-year range. There were 13 males and 8 females; two of the children were black and 19 were white. The children ranged in chronological age from 6.5 years to 11.6 years, with a mean age of 8.6 years. Instruments

McCarthy Scales of Children’s Abilities. The MSCA consists of six scales, each of which yields a composite raw score that is converted to a standard score according to the chronological age of the child (McCarthy, 1972). McCarthy also provided a table of MAS for the General Cognitive Scale based upon the formula MA = GCI XCA/ 100. These MAS can, therefore, be established only for children for whom it is possible to table a GCI, and they are not based upon the actual performance of the children in the standardization sample. In the present study, Kaufman and Kaufman’s tables of MAS for the General Cognitive and the other five scales of the MSCA were used. These MA scores were established for each of the six scales by determining the average raw score obtained by children in the standardization sample at each chronological age tested, from 2Y2 to 8%. The principle underlying these MAS is that the mean raw score obtained by children in the standardization sample of a given age, in a given scale, reflects the typical performance of children of this age (Kaufman & Kaufman, 1977). The conver- sion of a raw score to an MA score, with the Kaufman and Kaufman tables, is made in- dependently of the child’s Index scores and requires only that the level of intellectual and motor functioning be within the 2%- to 8Y2-year age range.

Minnesota Child Development Inventory. The MCDI is a standardized test of 320 items designed to assess the development of children in the first 6% years of life based upon a mother’s observations (Ireton, 1974). From her description of the child, DA es- timates are derived in eight areas: General Development, Gross Motor, Fine Motor, Ex- pressive Language, Comprehension-Conceptual, Situation Comprehension, Self-Help, and Personal-Social. Items comprising the MCDI were selected from a large pool of behavioral descriptions on the basis of content, and were validated on a sample of 887 white children in Minnesota (44 1 males, 446 females). The most age-discriminating items were selected for final inclusion in the MCDI. The MCDI was then validated on a separate sample of 796 white suburban children 6 months to 6% years of age. Norms by age and sex were established in the form of DAs from this sample of 796 children (395 males, 40 1 females). Handicapped children were excluded from the normative sample. DAs were established according to the same principle as that used by Kaufman and Kaufman (1977) to establish MSCA MAS. That is, the mean raw score obtained, for ex- ample, by 4-year-olds in the normative sample was established as corresponding to a DA

308 Use of the MSCA

of 4 years (Ireton, 1974). Reliability (internal consistency) and discriminative validity studies yielded adequate psychometric support for its use. In the present study, DAs from the General Development Scale of the MCDI were chosen to compare with MSCA and Stanford-Binet MAS. It is the most age-discriminating scale and provides an overall index of development. (Ireton, 1974).

Stanford-Binet Intelligence Scale. The Stanford-Binet (Terman & Merrill, 1973) is a professionally administered individual test of intelligence. It yields a global measure of intellectual functioning, the IQ, which is a standard score with a mean of 100 and a stan- dard deviation of 16. In addition, the Stanford-Binet provides MA scores, which were the scores of main interest in this study. The procedure for obtaining an MA with the 197.2 revision of the Stanford-Binet is the same procedure used with the 1960 and 1937 revisions. However, children comprising the 1972 norming sample of the Stanford-Binet, particularly preschool children, performed significantly better than did the children com- prising the 1930 norming sample, altering the classic relationship between MA, CA, and IQ (Terman & Merrill, 1973). For example, between the ages of 2Y2 and 6Y2, it is necessary for a child to obtain an MA 5 to 6 months greater than his or her chronological age in order to receive an average IQ of 100 (Terman & Merrill, 1973). Thus, a 10-year- old mentally retarded child who obtained an MA of 5 years would not be performing like the average 5-year-old (as would a 10-year-old mentally retarded child who obtained an MSCA MA of 5 years), but rather would be performing like the average 4R-year-old. Whereas a given MSCA or MCDI MA reflects the average performance of children of that age, a given Stanford-Binet MA often reflects the average performance of children several months younger than that age. In the present study, in order to make the Stanford-Binet MAS comparable in meaning to the MSCA MAS and the MCDI DAs, a “corrected” Stanford-Binet MA was tabled for each subject. This was done by taking each child’s MA score as derived from the Stanford-Binet test protocol, locating in the Stanford-Binet norms table the mean (100) corresponding to this MA, and then locating the corresponding chronological age for that mean. This chronological age was then es- tablished as the child’s “corrected” MA score. This correction had the effect of lowering individual MA scores by 3 to 6 months and the mean MA from 47.3 months (standard deviation=8.3 months) to 41.8 months (standard deviation=7.8 months). The corrected M A scores were used in all analyses.

Procedure For each child, an MCDI was completed by the child’s mother and by an

educational caregiver. Educational caregivers were 10 teachers and 1 1 teacher’s aides. Educational caregiver-completed MCDIs served as reliability checks for mother- completed MCDIs. The mean length of time that the educational caregivers had been in- structing the child (children) for whom they completed an MCDI(s) was 8.24 months. In all cases but one, the mother had been caring for her child since birth. In most cases, MCDIs were completed approximately two weeks prior to the first professional assess- ment (mean=11 days). The mean amount of time between mother’s and educational caregiver’s completion of the MCDI was 3 days, with a range of 0 to 14 days.

The Stanford-Binet and the MSCA were administered according to their standard- ization procedures in the school setting by four trained examiners supervised by a licensed clinical psychologist. The order of administration of the Stanford-Binet and the MSCA was counterbalanced such that 1 1 children were administered the Stanford-Binet first and 10 children were administered the MSCA first. The mean interval of time that

Use of the MSCA 309

elapsed between the two professional assessments was 8 days, with a range of 1 to 21 days.

RESULTS AND DISCUSSION MCDI Interjudge Reliability

DA estimates derived from the General Development Scale of mother- and educational caregiver-completed MCDIs correlated highly (r= .86, p < .001). Because chronological age correlated significantly with the MCDI DAs (.36, p<.05 with mother- completed MCDIs and .46, p<.02 with teacher-completed MCDIs), the data were analyzed using partial correlations. With the effects of chronological age removed, the DA scores correlated .83, p<.OOl, indicating good interjudge reliability between mothers and educational caregivers. The mean mother General Development DA of 45.1 months (standard deviation= 13.1) was compared to the mean educational caregiver General Development DA of 41.1 months (standard deviation = 11.9) by means of a correlated t- test. The mean DAs were significantly different, t(20)=2.68, p<.OI.

TABLE I Pearson Product-Moment Intercorrelations and Partial Interrorrelalions for

Chronological Age, M S C A M A S . Stanford-Binet M A S , and MCDI DAs

Chronological Age Stanford-Binet MCDI partial partial correla- correla-

r r tion r tion

MSCA General Cognitive .21(N.S.) .69 .69 .73 .72

Motor Verbal

.36@< .05) .69 .69 .67 .62

.07(N.S.) .56 .56 .6 1 .63

Perceptual-Performance .4 1@< .03) .65 .66 .70 .65

Memory .16(N.S.) .65 .65 .66 .65

Quantitative .37@<.05) .67 .68 .76 .72

Stanford-Binet .13(N.S.) MCDI"

General Development .36@<.05) .67 .67

completed by mothers Note. All scale correlations and partial correlations significant at p<.005.

MSCA Concurrent Validity Pearson product-moment intercorrelations and partial intercorrelations of

chronological age, MSCA MAS, the corrected Stanford-Binet MAS, and the mother MCDI General Development DAs are presented in Table I . The partial correlation of the MSCA General Cognitive MAS with the corrected Stanford-Binet MAS was .69 and with the mother MCDI General Development DAs was .72. The partial correlations of the five MSCA subscale MAS with the corrected Stanford-Binet MAS ranged from .56 to .69 and with the mother MCDI General Development DAs ranged from .62 to .72. All partial correlations were significant at p<.005.

310 Use of the MSCA

Mean M A Diferences Table 2 contains the means and standard deviations of the MA scores obtained from

the three tests. A one-way analysis of variance for repeated measures performed on the Stanford-Binet MAS, mother MCDI General Development DAs, and the MSCA MAS yielded an F(2, 40)=2.30, N.S.

TABLE 2 MSCA M A S , Stanford-Binet MAS. and MCDI DAs:

Means and Siandard Deviations in Months

M S D

MSCA MAS General Cognitive 41.4 5.7 Verbal 40.3 5.4

Perceptual-Performance 42.6 9.5

Quantitative Memory Motor

41.4 7.8

41.4 6.8 43.4 11.5

Stanford-Binet MAS Corrected* 41.8 7.8

Uncorrected 47.3 8.3

MCDIbDAs Mothers 45.1 13.1 Teachers 41.1 11.9

'corrected for 1972 cohort effects bMCDI=General Development Scale

MSCA Standard Scores Eleven subjects in this sample of moderately mentally retarded children were 8 1/2

years or younger and therefore age appropriate for the MSCA standard score norms. It was, therefore, possible to attempt to table GCIs and subscale Indexes for them. However, for 10 of these 11 children, GCIs could not be tabled because their raw scores fell more than 4% standard deviations below the mean for their chronological age and they could only be assigned GCIs of less than 28 according to Harrison and Naglieri's (1978) table of extrapolated GCIs. MSCA subscale Indexes could be tabled for only one subject. Stanford-Binet IQs for these 11 children ranged from 31 to 65, with a mean of 50.46 (standard deviation =9.09). For nine of these children, Stanford-Binet IQs were more than 17 points higher than GCIs, if the GCI was established at 28.

This study investigated the validity and utility of the MSCA when used to assess the abilities of a sample of moderately mentally retarded children. The results suggest that the MSCA MA scores provided by Kaufman and Kaufman (1977) are valid estimates of the abilities of moderately mentally retarded children. MAS from the MSCA General Cognitive, Motor, Verbal, Perceptual-Performance, Memory, and Quantitative scales correlated significantly and moderately high with both Stanford-Binet MAS and mother MCDI General Development DAs. There were no significant differences among mean scores for the MSCA General Cognitive Scale, the Stanford-Binet, or the mother MCDI

Use of the MSCA 31 1

General Development Scale when these scores were expressed as MAS. These results suggest that the MSCA, Stanford-Binet, and MCDI measure similar abilities in men- tally retarded children, and that the MSCA tasks are not inherently too difficult for retarded children.

The results on a subsample of 11 children age appropriate for the MSCA norms (i.e., chronological age was less than 89'2 years) replicate those of other investigators who have used MSCA standard scores to describe the performance of mentally retarded children. For 10 of these 11 children, a GCI could not be tabled despite the availability of Harrison and Naglieri's table of extrapolated values that extend GCIs 4% standard deviations below the mean. The General Cognitive Scale performance of these children could only be described as less than 28. For all but two children, MSCA GCIs were widely discrepant from Stanford-Binet IQs. The Stanford-Binet IQs were more than 17 points higher than the MSCA GCI floor level of 28. The results from other studies and the present one suggest that the normative tables for the GCI presented by McCarthy (1972) and their extrapolation by Harrison and Naglieri (1978) are likely to seriously un- derestimate the IQ scores of mentally retarded children. Therefore, a mentally retarded child's GCI should not be viewed as interchangeable with an IQ score for diagnostic and classification purposes.

Despite the positive findings in this study on the validity of the MSCA MA scores provided by Kaufman and Kaufman (1977), the utility of these scores must be called into question. For several reasons, the utility of MSCA MAS for assessing the abilities of mentally retarded children may be limited. MA scales are less psychometrically rigorous than standard score scales, and a profile of MA scores is much less exact than a profile of standard scores (Kaufman & Kaufman, 1977). The most salient limitations of an MA scale, calling for cautious use and interpretation of MA scores both within and between children, are that equality of units throughout an MA scale cannot be assumed, different abilities measured by an MA scale may proceed at different rates, and children receiving the same MA score may be qualitatively different (Thorndike & Hagen, 1977).

On a more practical level, the issue of determining where a child is performing in relation to his same-age peers and the issue of classification cannot be addressed when MA scores are used. MA scores, no matter how valid or useful for descriptive purposes, cannot serve this function. When children suspected of mental retardation are to be assessed and standard scores are required for diagnosis, the MSCA cannot be recommended. Again, the problem with the MSCA does not appear to lie in the difficulty of the tasks it includes, but in the translation of a mentally retarded child's performance into standard scores. The practical applications of the MSCA, in its current form, are therefore circumscribed.

Thorndike and Hagen (1977) have noted that MA scales are least problematic and most applicable when used for assessing such traits as general intelligence in young children. Therefore, for children already classified and known to be functioning developmentally in the 2Y2- to 8'/2-year age range, MSCA MAS may have some utility for description of abilities and estimation of strengths and weaknesses.

312 Use of the MSCA

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