Utility of a clinically derived abbreviated form of the WAIS-III

Transcription

1 Archives of Clinical Neuropsychology 18 (2003) Utility of a clinically derived abbreviated form of the WAIS-III Joy H. Wymer, Katrina Rayls 1, Mark T. Wagner 2 Psychological Assessment Center, Medical University of South Carolina, Charleston, SC, USA Accepted 4 September 2002 Abstract The Wechsler Adult Intelligence Scale Third Edition (WAIS-III) often poses problems for many populations due to the length of administration. Twenty geriatric subjects were administered the full WAIS-III. Three abbreviated forms of the WAIS-III (Satz Mogel abbreviation (Satz & Mogel, 1962); seven-subtest short form (Ward, 1990); and a clinically derived abbreviation) were evaluated by rescoring original full WAIS-III protocols. Results showed that the abbreviated WAIS-III protocols were highly correlated with complete protocols, and classification rules were the highest for the clinically derived abbreviation. The clinically derived abbreviation was reevaluated in a college LD/ADHD population yielding similarly high correlations. Results support the use of abbreviated forms of the WAIS-III in the evaluation of elderly patients and young adults, and point to the clinically derived abbreviation as providing the smallest discrepancies from FSIQ National Academy of Neuropsychology. Published by Elsevier Science Ltd. All rights reserved. Keywords: WAIS-III; Abbreviation; Short-form; Assessment; Elderly The Wechsler Adult Intelligence Scale (WAIS), in its various revisions, has been the gold standard for the assessment of intelligence in the United States. The utility of a measure of intelligence in the assessment of various disorders, including Learning Disabilities, Attention Deficit/Hyperactivity Disorder, and neurological conditions, is widely documented, and using the WAIS series has long been common practice. The advent of the Wechsler Adult Intelligence Corresponding author. Present address: Department of Psychology, Louisiana State University, 236 Audubon Hall, Baton Rouge, LA , USA. Tel.: ; fax: address: jhwymer@hotmail.com (J.H. Wymer). 1 Neurobehavior Clinical Research Program, University of Utah Health Sciences Center, UT, USA. 2 Department of Neurology, Medical University of South Carolina, Charleston, SC, USA /$ see front matter 2002 National Academy of Neuropsychology. doi: /s (02)

2 918 J.H. Wymer et al. / Archives of Clinical Neuropsychology 18 (2003) Scale Third Edition (WAIS-III) has increased the range of this measure by offering extended upper age normative data. Not only does the WAIS-III measure a variety of abilities, it is more useful for a geriatric population than past revisions. Several factors, however, may interfere with the utility of this measure in the mentioned populations. First, patient endurance often dictates shorter exams, especially in the geriatric population. The WAIS-III manual states that the average administration time for the entire measure ranges from 60 to 90 min (Wechsler, 1997). Other researchers have suggested while the adults in the standardization sample may complete the WAIS-III within these time limits, the psychiatric or geriatric patient often takes significantly longer, possibly up to 2 hours (Ryan, Lopez, & Werth, 1998). Such evaluations frequently result in fatigue, frustration, and decreased motivation in these patient populations thereby decreasing the measure s psychometric properties. Second, time constraints dictated by third party reimbursement may make lengthy evaluations obsolete. Abbreviated versions of intelligence tests have been available as long ago as the first half of the 20th century when Doll (1917) published an abbreviated version on the Stanford Binet Intelligence Scale (as cited in Bersoff, 1971). Twenty years later, Terman and Merrill (1937) selected four subtests of the Stanford Binet, based on age, to be administered as abbreviated versions. These abbreviated versions were to be administered when time constraints dictated their use. Since an early four-subtest abbreviation of the Wechsler scale in 1956 (Doppelt), many researchers have searched for the most psychometrically sound abbreviated version of this measure. One of the main reasons for the search is a need for reduced test taking time. An abbreviated form should reduce testing time by about 50% (Levy, 1968). Abbreviated forms of the major intelligence tests, such as the Wechsler Intelligence Scales, are generally preferred to briefer measures of IQ, such as the Slosson Intelligence Test or the Shipley Institute of Living Scale, because of the superiority of their normative samples, reliability, and breath of research (Hoffman & Nelson, 1988). Additionally, for some individuals, a lengthy IQ evaluation is unnecessary and serves no further purpose other than that which can be reached by administering a abbreviated version. Examples of these situations include: individuals requiring a psychological evaluation with only an IQ estimate; those who have been completely evaluated recently and simply need an updated measure of intellectual status; or for group screening for the purposes of further follow up (Kaufman, Ishikuma, & Kaufman-Packer, 1991). Abbreviated IQ tests might be inadequate for classification purposes, but are generally considered acceptable as screeners to obtain IQ estimates when IQ is not the primary focus (Ryan & Rosenberg, 1984). Many abbreviations of the WAIS and Wechsler Adult Intelligence Scales Revised (WAIS-R) have been derived and evaluated. Different researchers judge their abbreviated versions according to different criteria and, therefore, make comparisons across derived measures differently. Resnick and Entin (1971) proposed that the following three validation criteria be used to identify a successful abbreviation: (1) the abbreviated version IQ should significantly correlate with the Full Scale IQ (FSIQ) and, according to Nunnally (1978), have reliabilities equal to.90 or higher, (2) the difference between the abbreviated form estimated IQ mean and the FSIQ mean should be nonsignificant, and (3) using ranges identified in the manuals, abbreviated form classifications should be identical to FSIQ classifications in a large percentage of cases. The third criterion is especially problematic. Using this as a benchmark for success,

3 J.H. Wymer et al. / Archives of Clinical Neuropsychology 18 (2003) abbreviated form IQ s differing from FSIQ s by 1 point could fail this requirement, while those differing by 19 points might not. Because these criteria are potentially inaccurate, Thompson, Howard, and Anderson (1986) proposed a fourth validation criterion to clarify results: the abbreviated form IQ should fall within the 95% confidence interval in a high percentage of cases. Other researchers (Bersoff, 1971) have suggested that high correlations might be misleading, therefore not only should correlations be reported, but also the absolute differences between means, range of differences, and direction of error. Different types of WAIS-III abbreviations have been developed over the years. The most common two are select-subtest and select-item abbreviations. Select-item abbreviations typically involve the administration of previously selected items from all subtests. Based on the breath of literature, select-subtest versions are more widely used. Luszki, Schultz, Laywell, and Dawes (1970) identified four types of test abbreviations. In addition to the decision to eliminate certain subtests or certain items within the subtests, the eliminations can be based on either an empirical or a statistical basis. An empirical selection is based on variables such as client special needs, education, cultural background, time limits, or examiner preferences. A statistical selection may involve selecting subtests or items based on correlations or factor analyses. Many select-subtest abbreviations have been researched, ranging from two to seven subtest versions. The three most widely used and researched select-subtest versions appear to be Silverstein s (1982) two- and four-subtest abbreviations and Ward s (1990) seven-subtest abbreviation. Silverstein s two-subtest abbreviation consists of Vocabulary and Block Design and the four-subtest abbreviation consists of Vocabulary, Arithmetic, Block Design, and Picture Arrangement. These combinations were chosen because of their high correlations with FSIQ. Silverstein offers tables for estimating FSIQ for both of these versions. There are concerns that while the Silverstein abbreviations may provide a general estimate of FSIQ, they tend to be biased in the direction of overestimating IQ (Thompson et al., 1986), with the two-subtest abbreviation being more likely to provide an overestimate. Ward s (1990) seven-subtest version of the WAIS-R, includes Information, Digit Span, Arithmetic, Similarities, Picture Completion, Block Design, and Digit Symbol. This abbreviation takes an estimated 41 min to administer (Paolo & Ryan, 1993b) and has received mixed reviews. One of its benefits is the derivation of estimates for Verbal (VIQ) and Performance (PIQ), as well as FSIQ. Of these three indices, Axelrod and Paolo (1998) found the FSIQ estimate to be the most comparable to the full administration, followed by the VIQ, and then PIQ scores. They concluded that the Ward abbreviation is appropriate to use for the derivation of FSIQ and VIQ estimates, but acknowledged a limitation that the estimates resulted in reduced reliability and had a larger standard error of measurement. Guilmette, Dabrowski, Kennedy, and Gnys (1999) examined the psychometric properties in several select-subtest abbreviations with a brain injured population. They applauded the Ward seven-subtest abbreviation as being superior to other selected abbreviations in mean absolute difference scores between estimated and actual FSIQ, the percentage of patients with precisely predicted FSIQ s, and the range of absolute difference scores. However, the Ward abbreviation tended to overestimate IQ. In addition to these more popular select-subtest abbreviations, there are many other researched versions. Miller, Streiner, and Goldberg (1996) analyzed all possible subtests combinations and found each to provide an accurate estimate of the FSIQ. In general, as the number of subtests increased, the predictive accuracy increased slightly. As a result, Miller et al.

4 920 J.H. Wymer et al. / Archives of Clinical Neuropsychology 18 (2003) concluded that the search for the best possible subtest combination might be futile. Researchers have deleted and added subtests in attempts to find the perfect selection of subtests. The data indicate that not only is there not a perfect subtest combination for an abbreviated version, but that the best select-subtest combination may in fact vary as a function of the type of client (Guilmette et al., 1999). There have been many arguments against the use of select-subtest abbreviations. Some researchers (Roth, Hughes, Monkowski, & Crosson, 1984; Ryan, 1983; Ryan, Larsen, & Prifitera, 1983; Zubicaray, Smith, & Anderson, 1996) have identified one or more problems with many of the select-subtest abbreviated forms. These problems include complaints that the abbreviated versions provide only a very rough estimate of FSIQ, may be positively biased with clinical populations, misclassify large percentages of individuals, and provide uninterpretable Verbal-Performance IQ discrepancies. Next to the select-subtest abbreviations, Satz and Mogel (1962) developed one of the most widely used select-item abbreviations. The Satz Mogel abbreviation was developed because of the most obvious limitations of the select-subtest abbreviations, the emphasis on single IQ indices and the sacrifice of those very functions which are so helpful in interpreting the breadth of intellectual performance from the WAIS (p. 77). The original Satz Mogel abbreviation of the WAIS required the administration of all subtests. Every third item was administered on the Information, Vocabulary, and Picture Completion subtests; odd items were administered on the Comprehension, Arithmetic, Similarities, Block Design, Picture Arrangement, and Object Assembly subtests; and Digit Span and Digit Symbol were administered in their entirety. The Information and Block Design subtests were further weighted by subtracting 1 point from the final raw score. Index correlations between the Satz and Mogel (1962) abbreviation and full WAIS ranged from.99 (FSIQ and VIQ) to.97 (PIQ); Verbal subtest correlations ranged from.97 (Information) to.89 (Vocabulary); and Performance subtest correlations ranged from.92 (Picture Completion) to.77 (Object Assembly). Over 90% of estimated IQ scores came within 4 points of actual IQ scores. The Satz Mogel correlations were consistently high regardless of intellectual classification or diagnostic category. This is a unique characteristic of the Satz Mogel abbreviation, as many other abbreviations, especially select-subtest abbreviations, tend to vary in the strength of their correlations as IQ deviates further from the mean. As with the Ward (1990) abbreviation, the Satz Mogel PIQ estimate has been found to be somewhat less stable than the Verbal and Full Scales (Paolo & Ryan, 1993a). Researchers suggest that the Satz Mogel abbreviation is appropriate for various populations including psychiatric inpatients (Hyer & Harkey, 1984), normal elderly persons (Paolo & Ryan, 1993b), elderly patients with dementia (Osato, Van Gorp, Kern, Satz, & Steinman, 1989), patients with Parkinson s disease (Albrecht et al., 1994), and patients with head injuries (Robiner, Dossa, & O Dowd, 1988). When compared to Silverstein s (1982) two- and four-subtest abbreviations, the Satz Mogel abbreviation of the WAIS-R resulted in fewer misclassifications in a brain injured sample (Robiner et al., 1988). Robiner et al. (1988) concluded that the Silverstein abbreviations are more likely to result in inaccurate or inflated IQ estimates (p. 370). Although the WAIS-III has been available since 1997, there has been very little research on updating previously utilized abbreviated versions of the WAIS-R. The majority of existing

5 J.H. Wymer et al. / Archives of Clinical Neuropsychology 18 (2003) research has focused on the development of new select-subtest abbreviations for the WAIS-III, especially the Ward (1990) seven-subtest abbreviation (Axelrod, Ryan, & Ward, 2000, 2001; Pilgrim, Meyers, Bayless, & Whetstone, 1999; Ryan, 1999; Ryan & Ward, 1999). The newest seven-subtest abbreviation includes six of the same subtests, but substitutes Matrix Reasoning for Block Design (Ryan, 1999). There is limited research on the Ward abbreviation of the WAIS-III, but the same benefits and problems appear to persist. Few resources have been devoted to updating the select-item abbreviations, which proponents suggest may provide more accurate estimates of FSIQ. Ryan, Lopez, and Werth (1999) published a preliminary validation study on an updated version of the Satz Mogel abbreviation of the WAIS-III with a substance abuse population. They demonstrated high correlations between the subtests on the full and abbreviated forms and IQ s within 6 points of the WAIS-III in more than 80% of cases. Alternatively, an abbreviated Wechsler intelligence test was developed in The Wechsler Abbreviated Scale of Intelligence (WASI) was created with the aforementioned problems of time constraints and third party reimbursement in mind. The WASI may be comprised of two or four subtests, with the two-subtest version yielding only FSIQ, and the four-subtest version yielding VIQ, PIQ, and FSIQ. Estimated administration times are 15 min for the two-subtest version and 30 min for the four-subtest version (Wechsler, 1999). WASI VIQ and PIQ scores are correlated with WAIS-III VIQ and PIQ (r =.88 and.84, respectively). WASI FSIQ correlations with the WAIS increase as a function of the number of subtests included (i.e., two-subtest version: r =.87; four-subtest version: r =.92;) (Wechsler, 1999). The benefits of the WASI are a large representative normative sample and short administration time. The limitations are the same as those mentioned with regard to other select-subtest abbreviations, that is, the breath of intellectual functioning is reduced to one or three general scores and the information about specific cognitive capacities is limited. Additionally, investigation of the WASI supports the notion that fewer subtests lead to lower validity. Although additional research on an update of the Satz and Mogel (1962) abbreviation is needed, some concerns regarding the need for the use of all subtests and administration procedures exist. These concerns led to the empirical development of a hybrid version of the Satz Mogel abbreviation based on behavioral observations of patients during the administration of the WAIS-III. The time requirements of each subtest, number of items, perceived level of difficulty/frustration, and correlation with FSIQ were considered when developing a clinically derived abbreviation of the WAIS-III based on a select-item/subtest procedure. 1. Study Method Participants Subjects included 20 patients consecutively seen for dementia evaluations in the outpatient based neurology clinic at the Medical University of South Carolina in Charleston. The

6 922 J.H. Wymer et al. / Archives of Clinical Neuropsychology 18 (2003) subjects ranged in age from years (Mean = 73.15; S.D. = 6.268) with a mean education level of years (S.D. = 3.98; Range = 3 16 years). The sample included 7 male (35%) and 13 female (65%) patients. The sample was made up of 15 Caucasians (75%) and 5 African Americans (25%). The criteria developed by the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer s Disease and Related Disorders Associations (NINCDS & ADRDA; McKhann et al., 1984; Morris et al., 1989; Teirney et al., 1988) were used to identify Alzheimer s Dementia severity ratings in subjects. Analysis revealed subjects predominantly in the normal (eight subjects; 42.1%) and mild (eight subjects; 42.1%) ranges with two subjects (10.5%) falling into the moderate range and two subjects (10.5%) in the questionable range. Subjects in the severe and profound ranges were excluded from our sample due to an inability to complete one or more WAIS-III subtests Procedure The WAIS-III was administered to subjects by postdoctoral residents as part of a comprehensive neuropsychological evaluation. Average administration time of the full WAIS-III was 61 min (S.D. = 16.7; Range = 45 85). Three abbreviated forms (a modified Satz Mogel abbreviation (Satz & Mogel, 1962), Ward s (1990) seven-subtest abbreviation, and a clinically derived abbreviation) were rescored from original full WAIS-III protocols. Scoring procedures for the abbreviated forms are identified in Table 1. The clinically derived abbreviation was based on observations of patients behavior. Specifically, subtests that were observed to be lengthy or frustrating and did not seem to add useful information to the interpretation were abbreviated or not scored. The style of this clinical derivation was partially based on the Satz and Mogel (1962) procedure, in which all subtests are administered and administered items in a subtest include all items, odd items, or every third item (beginning with Item 3 and proceeding). In the scoring of the clinically derived abbreviation, Object Assembly was not included because it is an optional subtest in the WAIS-III and provides little additional information. Picture Arrangement Table 1 Items/subtests administered in three different WAIS-III abbreviations Subtest Clinically derived version Modified Satz Mogel (1962) version Ward (1990) seven-subtest version Picture Completion All Every third item All Vocabulary Every third item Every third item Not administered Digit Symbol All All All Similarities Odd items Odd items All Block Design All Odd items All Arithmetic Odd items Odd items All Matrix Reasoning Odd items All Not administered Digit Span All All All Information Every third item Every third item All Picture Arrangement Not administered Odd items Not administered Comprehension Odd items Odd items Not administered

7 J.H. Wymer et al. / Archives of Clinical Neuropsychology 18 (2003) scores were also disregarded because correlations between this subtest and IQ scales vary widely among age groups. Additionally, it is a lengthy subtest to administer. Since Picture Completion has a short administration time it was scored in its entirety. The entire Block Design subtest was scored because there appears to be a practice effect that occurs when items are administered consecutively rather than only odd items. Odd items in Matrix Reasoning were scored in the clinically derived version and this subtest was scored in its entirety in the Satz Mogel abbreviation in an attempt to update the Satz Mogel version while maintaining its integrity. Other than the aforementioned changes, the clinically derived abbreviation was developed using the rationale of the original Satz Mogel abbreviation. Raw subtest scores were then multiplied by the appropriate factor if the entire subtest was not given (i.e., 3 if every third item was administered and 2 if every other item was administered). Age corrected subtest scores, index scores, and IQ scores were calculated based on the adjusted raw scores using the WAIS-III age appropriate normative data Results Results showed that the abbreviated WAIS-III protocols were highly correlated with complete protocols (see Table 2). Specifically, individual subtest scores from the abbreviations were highly correlated with original WAIS-III subtest scores with correlations ranging from r =.95 (Comprehension) to.97 (Similarities) for the clinically derived abbreviation and from.91 (Picture Arrangement) to.97 (Similarities) for Satz Mogel abbreviation. Satz Mogel and clinically derived abbreviations correctly diagnostically classified IQ category (Average, Low Average, etc.) in 95% of cases; the seven subtest version correctly classified IQ category in 90% of cases. Estimated FSIQ s based on the clinically abbreviated version were identical to actual FSIQ s most frequently (35% identical scores) (see Table 3). Table 2 Correlations between full WAIS-III indices and abbreviated forms in an elderly sample Clinically derived version Satz Mogel version Ward seven-subtest version VIQ r =.986 r =.991 r =.979 PIQ r =.987 r =.984 r =.982 FSIQ r =.994 r =.992 r =.990 Table 3 Discrepancies between obtained WAIS-III FSIQ s and abbreviated FSIQ s in an elderly sample Clinically derived version Satz Mogel version FSIQ hits (exact matches) FSIQ discrepancy range (points) Note. Points reported in standard score points. Ward seven-subtest version

8 924 J.H. Wymer et al. / Archives of Clinical Neuropsychology 18 (2003) Study 2 Since the clinically derived abbreviation of the WAIS-III proved to be comparable to other abbreviated versions (i.e., Satz Mogel and Ward seven-subtest abbreviations) in an older adult population, its utility in a young adult population will be assessed for further validation Method Participants Subjects included 20 patients consecutively seen for ADHD/LD evaluations in an outpatient based neuropsychology clinic at the Medical University of South Carolina in Charleston. The subjects ranged in age from years (Mean = 22.75; S.D. = 5.794) with a mean education level of 12.9 years (S.D. = 1.619; Range = 8 15 years). The sample included 9 male (45%) and 11 female (55%) patients; 17 Caucasians (85%), 2 African Americans (10%), and 1 Asian (5%) Procedure To continue the evaluation of the psychometric properties of the clinically derived abbreviated WAIS-III, the abbreviation described in Study 1 (see Table 1) was studied in a sample of college students referred for LD/ADHD evaluations. The WAIS-III was administered as part of a comprehensive LD/ADHD evaluation. The full WAIS-III protocols were rescored according to the clinically derived abbreviation Results The abbreviated form IQ scores, resulting from the clinically derived abbreviation, were highly correlated with complete WAIS-III IQ scores (VIQ: r =.971; PIQ: r =.929; FSIQ: r =.980). Correlations between abbreviated and full individual subtests ranged from.83 to.92. The abbreviated version correctly classified IQ category (Average, Low Average, etc.) in 85% of cases. Discrepancies were calculated between obtained full WAIS-III FSIQ and abbreviated WAIS-III FSIQ s. Mean discrepancies were small for the abbreviated form (Range = 0 6 points). 3. Discussion In comparing the current abbreviations of the WAIS, including the WASI, all versions appear to meet the criteria of administration time reduction by at least 50%. Therefore, in making a choice between measures, neuropsychologists may need to consider the type of information desired by administration of an intelligence test. Although a general IQ score is useful in comparison to baseline function, measurement of underlying cognitive domains, as assessed by individual WAIS-III subtests, are more relevant with respect to the typical goals of the neuropsychological evaluation. When shorter evaluations are necessitated, select item abbreviations retaining all or most of the subtests provide the greatest wealth of information.

9 J.H. Wymer et al. / Archives of Clinical Neuropsychology 18 (2003) When following medical/neurology patients, consistency between instruments at reevaluations can improve the interpretability of results. It may be unnecessary to give a complete WAIS-III every 6 12 months, but an abbreviated version that will yield similar scores is helpful in continued treatment planning. Results of this study indicate that an abbreviation of the WAIS-III is feasible without significantly compromising overall results. The clinically derived abbreviation resulted in more exact FSIQ hits (identical scores) than other abbreviations, high diagnostic classification accuracy, and is based on an empirically and statistically supported rationale for test inclusion (e.g., patient tolerance). These factors render the clinically derived abbreviation a good choice. Some limitations of these studies include the small sample sizes, which might have resulted in limited generalizability. Although the results were consistent across samples, further evaluation of the clinically derived abbreviation with different and larger samples might add support to its use. In this study, protocols were administered entirely and then rescored according to the various abbreviations. It has been suggested in the literature that this method might yield different results than would be expected if only the abbreviated versions had been administered. One of the main concerns regarding full WAIS-III administration is the ensuing fatigue, which might result in inaccurately deflated scores. Future research should compare administered abbreviated versions with FSIQ s, keeping in mind that slightly higher estimated FSIQ s should be expected since fatigability had been reduced. References Albrecht, N. N., Netherton, S. D., Elias, J. W., Albrecht, J. W., Whitfield, K. E., & Hutton, J. T. (1994). Assessment of intellectual functioning of patients with Parkinson s disease using the Satz Mogel (1962) short form of the Wechsler Adult Intelligence Scale. Experimental Aging Research, 20, Axelrod, B. N., & Paolo, A. M. (1998). Utility of the WAIS-R seven-subtest short form as applied to the standardization sample. Psychological Assessment, 10, Axelrod, B. N., Ryan, J. J., & Ward, C. L. (2000). Estimation of Wechsler Adult Intelligence Scale-III index scores with the 7-subtest short form in a clinical sample. Assessment, 7, Axelrod, B. N., Ryan, J. J., & Ward, C. L. (2001). Evaluation of seven-subtest short forms of the Wechsler Adult Intelligence Scale-III in a referred sample. Archives of Clinical Neuropsychology, 16, 1 8. Bersoff, D. N. (1971). Short forms of individual intelligence tests for children: Review and critique. Journal of School Psychology, 9, Doppelt, J. E. (1956). Estimating the Full Scale score on the Wechsler Adult Intelligence Scale from scores on four subtests. Journal of Consulting Psychology, 20, Guilmette, T. J., Dabrowski, J., Kennedy, M. L., & Gnys, J. (1999). A comparison of nine WAIS-R short forms in individuals with mild to severe traumatic brain injury. Assessment, 6, Hoffman, R. G., & Nelson, K. S. (1988). Cross-validation of six short forms of the WAIS-R in a healthy geriatric sample. Journal of Clinical Psychology, 44, Hyer, L. A., & Harkey, B. (1984). Satz Mogel short form of WAIS with older psychiatric patients. Psychological Reports, 55, Kaufman, A. S., Ishikuma, T., & Kaufman-Packer, J. L. (1991). Amazingly short forms of the WAIS-R. Journal of Psychoeducational Assessment, 9, Levy, P. (1968). Short-form tests: A methodological review. Psychological Bulletin, 69, Luszki, M. B., Schultz, W., Laywell, H. R., & Dawes, R. M. (1970). Long search for a short WAIS: Stop looking. Journal of Consulting and Clinical Psychology, 34,

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11 J.H. Wymer et al. / Archives of Clinical Neuropsychology 18 (2003) Wechsler, D. (1997). Manual for the Wechsler Adult Intelligence Scale-III. San Antonio, TX: The Psychological Corporation. Wechsler, D. (1999). Manual for the Wechsler Abbreviated Scale of Intelligence. San Antonio, TX: The Psychological Corporation. Zubicaray, G., Smith, & Anderson, D. (1996). Comparison of IQ s and verbal-performance IQ discrepancies estimated from two seven-subtest short forms of the WAIS-R. Journal of Psychoeducational Assessment, 14,