Concurrent validity of WAIS-III short forms in a geriatric sample with suspected dementia: Verbal, performance and full scale IQ scores

Transcription

1 Archives of Clinical Neuropsychology 20 (2005) Concurrent validity of WAIS-III short forms in a geriatric sample with suspected dementia: Verbal, performance and full scale IQ scores Brian L. Brooks a,, Linda E. Weaver a,b a Department of Psychology, University of Calgary, 2500 University Drive NW, Calgary, Alta., Canada T2N 1N4 b Seniors Health Ambulatory Care, Rockyview General Hospital, Calgary, Alta., Canada Accepted 10 June 2005 Abstract Evaluation of intellectual abilities using the WAIS-III is a common component of neuropsychological assessments. However, clinicians might be interested in administering reliable and valid short forms due to practical and clinical reasons. The present study examined the concurrent validity of eight short forms of the WAIS-III with full form IQ scores in a sample (n = 43) of geriatric outpatients referred for assessment of suspected dementia. There were no significant differences between the short and full form VIQ scores at P <.01, while half of the short form PIQ and FSIQ scores were significantly different from their respective full form scores at P <.01. Correlations between short and full form IQ scores ranged from.89 to.99. Seven-subtest short forms were able to accurately estimate over 80% of scores within ±2 S.E.M.s. This study supports limited use of WAIS-III short forms when conducting evaluations of older adults with suspected dementia National Academy of Neuropsychology. Published by Elsevier Ltd. All rights reserved. Keywords: WAIS-III; Elderly; Assessment; Dementia; Abbreviation; Short form 1. Introduction Psychological and neuropsychological evaluations of older adults often involve an assessment of intellectual abilities. One of the most widely used measures for evaluating intellectual Corresponding author. address: blbrooks@ucalgary.ca (B.L. Brooks) /$ see front matter 2005 National Academy of Neuropsychology. Published by Elsevier Ltd. All rights reserved. doi: /j.acn

2 1044 B.L. Brooks, L.E. Weaver / Archives of Clinical Neuropsychology 20 (2005) abilities has been the Wechsler Adult Intelligence Scale (WAIS; Wechsler, 1955, 1981, 1997). The popularity of the WAIS has come from its utility with various clinical populations and large amount of research literature. In addition, the most recent revision of the WAIS, the WAIS-III, has increased utility with geriatric patients compared to previous versions with the normative data extended up to the age of 89 years (Wechsler, 1997). Administration of the WAIS-III to obtain IQ scores includes six verbal (VIQ) and five performance (PIQ) subtests, with all 11 subtests contributing to a full-scale score (FSIQ). According to the WAIS-III manual, estimated administration time ranges from 60 to 90 min, but these times may increase to as long as two hours when being administered to some patient populations (Ryan, Lopez, & Werth, 1998), including geriatric patients with suspected dementia. One technique for reducing the amount of time spent testing intellectual abilities has been to employ short form versions of the WAIS, which involve only administering selected subtests to obtain estimated IQ scores. Ryan et al. (1998) reported that 10 of the 11 short forms they gave to patients reduced administration time by at least 50%. Some of the WAIS short forms have included seven-subtest versions derived by Ward (1990) and Paolo and Ryan (1993). Although these short forms were originally developed with the WAIS-R, the same abbreviated forms have been extended to the WAIS-III. Overall, many studies have reported that seven-subtest versions of the WAIS-III (i.e., Ward s; Paolo & Ryan s) can be substituted for the full WAIS-III with various clinical populations, as they are very highly correlated, provide estimates that are not significantly different from the original scores, and are generally able to accurately classify persons compared to the full version (Axelrod, Ryan, & Ward, 2001; Pilgrim, Meyers, Bayless, & Whetstone, 1999; Ryan & Ward, 1999). Accuracy of estimated scores with short form versions has been highest for VIQ and FSIQ scores, while the ability to estimate PIQ scores has been less reliable. For example, Axelrod (2002) found VIQ and FSIQ scores could be accurately estimated (97% of scores within ±10 points for both IQ estimates) with a four-subtest version of the WAIS-III, while the estimated PIQ scores were significantly higher than actual PIQ scores and only 76% of cases fell within ±10 points of the WAIS-III PIQ scores. Axelrod (2002) also examined the accuracy of another method for estimating IQ scores, the Wechsler Abbreviated Scale of Intelligence (WASI; Psychological Corporation, 1999). The WASI consists of four subtests (vocabulary, similarities, block design, and matrix reasoning, with different questions compared to the WAIS-III), has its own manual, normative data, and provides a table for estimating WAIS-III FSIQ scores from WAIS FSIQ scores. While the manual suggests the WASI should have strong concurrent validity with the WAIS-III, Axelrod (2002) found that abbreviated versions of the WAIS-III had higher accuracy compared to the WASI for VIQ, PIQ, and FSIQ scores in a mixed clinical sample. In addition, it took significantly longer to administer the WASI than the comparable four-subtest version of the WAIS-III. Further research is needed to examine the WASI and how it compares to abbreviated versions of the WAIS-III in various clinical samples. Studies examining the accuracy of WAIS-III short forms have used either normal controls or mixed clinical populations (e.g., Axelrod, 2002), and have typically only examined one or two short forms with the population of interest. Information regarding the accuracy of different short form versions of the WAIS-III with a geriatric population referred for assessment of suspected dementia is limited. Wymer, Rayls, and Wagner (2003) examined three abbreviated forms

3 B.L. Brooks, L.E. Weaver / Archives of Clinical Neuropsychology 20 (2005) [Ward s seven-subtest version, the Satz Mogel select-item version (Satz & Mogel, 1962), and a clinically derived select-item version] of the WAIS-III in a sample of 20 geriatric patients between the ages of 59 and 85 years with suspected dementia and found that all three short forms provided highly correlated scores (r s ranged from.98 to.99) and accurately classified the majority of FSIQ scores within the same categories (i.e., 90% in same category with Ward s seven-subtest, and 95% in same category with both the Satz Mogel and clinically derived versions). Although the three versions used in Wymer et al. (2003) provided nearly equivalent results, select-item versions (i.e., only administering selected items from all subtests) are not the most desirable (Sattler, 2001), especially with geriatric patients. Administering every second or third item in a subtest results in the difficulty of the items increasing two to three times as quickly compared to the original administration and reduces the amount of subtest-specific practice that is important on unfamiliar tasks. Given the lengthy history of abbreviated versions of the WAIS (Himelstein, 1957a, 1957b) and the continued use of brief measures of intellectual functioning (Thompson, LoBello, Atkinson, Chisholm, & Ryan, 2004), it is important to examine the accuracy of short form versions of the WAIS-III. Evaluating the utility of short form versions of the WAIS-III is critical for geriatric patients with suspected dementia, as the reduced tolerance for testing may necessitate using short forms of measures. In addition, it is important to extend the literature that examined short form versions of the WAIS-R in persons with suspected dementia (Margolis, Taylor, & Greenlief, 1986; Osato, Van Gorp, Kern, Satz, & Steinman, 1989; Randolph, Mohr, & Chase, 1993) to the updated WAIS-III. The purpose of this study was to examine the accuracy of eight short form versions of the WAIS-III in geriatric patients referred for neuropsychological assessment. Older adults can be susceptible to test fatigue and clinicians may need to consider abbreviated versions of measures during an assessment. Having information about older adults performance on short forms of the WAIS-III will help clinicians decide: (1) whether short forms are appropriate, and if they are, (2) which subtests to administer and (3) the level of clinical accuracy. 2. Methods 2.1. Participants Tests data was obtained from archival neuropsychological charts for outpatients referred for the investigation of suspected memory decline or general cognitive impairment. The sample (n = 43) consisted of 24 (56%) men and 19 (44%) women, with a mean age of 63.8 years (S.D. = 7.2; Range = 54 85) and 13.6 mean years of education (S.D. = 3.9; Range = 6 21). Regarding diagnoses, 65.1% had suspected dementia (39.5% had Alzheimer s dementia and 25.6% had vascular or mixed dementia), 20.9% had depression, and 14% had subjective, but not objective deficits (i.e., worried-well ). Suspected aetiologies for cognitive decline were given by a registered psychologist (LEW) and were based on clinical interview with patient and available family members, medical history, and comprehensive neuropsychological evaluation. Diagnostic criteria were based on the Diagnostic and Statistical Manual for Mental Disorders, fourth edition (DSM-IV; American Psychiatric Association, 1994).

4 1046 B.L. Brooks, L.E. Weaver / Archives of Clinical Neuropsychology 20 (2005) Table 1 Subtest combinations and prorating used for calculating verbal and performance IQ scores from short form versions of the WAIS-III Subtest combinations and prorating Version Verbal IQ Performance IQ Full WAIS-III V+S+I+A+DS+C PC+CD+BD+MR+PA Ward 7 a 2 (I+S)+DS+A 2 (PC+BD)+CD Paolo/Ryan 7 b 1.5 (I+A+DS+S) 1.67 (PC+CD+BD) Sattler 7 c 1.5 (I+A+DS+S) 1.67 (PC+CD+MR) Sattler 6 c 2 (I+V+S) 1.67 (PC+BD+MR) Sattler 5 c 2 (I+V+A) 2.5 (PC + MR) Sattler 4 c 3 (V + I) 2.5 (BD + MR) Sattler 3 c 3 (V+I) 5 (BD) Sattler 2 c 6 (V) 5 (MR) Note. V: Vocabulary; S: Similarities; A: Arithmetic; DS: Digit Span; I: Information; C: Comprehension; PC: Picture Completion; CD: Digit Symbol Coding; BD: Block Design; MR: Matrix Reasoning; PA: Picture Arrangement. FSIQ scores were calculated using the sums of the prorated VIQ and PIQ scores. a Ward (1990). b Paolo and Ryan (1993). c Sattler (2001) Procedure Participants were administered the full form WAIS-III. Data for short forms were obtained by re-scoring the original full WAIS-III protocol. Prorating of short form VIQ, PIQ and FSIQ scores was performed according to recommendations for seven-subtest versions from Ward (1990), Paolo and Ryan (1993), and Sattler (2001). In addition, six-, five-, four-, three- and two-subtest versions were selected from Sattler (2001) based on having the highest reliability and validity with the WAIS-III FSIQ in a non-clinical sample. A full list of the short form versions and calculations for prorating used in this study is provided in Table 1. FSIQ scores were calculated by adding the prorated VIQ and PIQ standard scores Analyses In order to examine the effectiveness of the different short form versions of the WAIS-III with this clinical population, different types of analyses were conducted for VIQ, PIQ, and FSIQ. First, repeated measures analyses of variance and correlations between the short form and full form scores were performed. To protect Type I error rate when performing multiple comparisons, significance was set at P <.01. Second, clinical accuracy was examined by calculating the percentage of short form scores that fell within ±2 standard errors of measurement (S.E.M.s) or within the same classification range. The S.E.M. for each IQ score was calculated as the average S.E.M. for the age groups above 55 years old in the standardization sample (see Wechsler, 1997, Table 3.4). For this study, 2 S.E.M.s for VIQ, PIQ, and FSIQ were 5.07, 7.04, and 4.50 points, respectively. Classification ranges were based on Wechsler (1997) and defined as: Extremely Low (standard score <70; <1st percentile); Borderline (standard score = 70 79;

5 B.L. Brooks, L.E. Weaver / Archives of Clinical Neuropsychology 20 (2005) th percentile); Low Average (standard score = 80 89; 10 24th percentile); Average (standard score = ; 25 75th percentile); High Average (standard score = ; 76 90th percentile); Superior (standard score = ; 91 97th percentile); and Very Superior (standard score >129; >97th percentile). 3. Results The following subtests were included in the analyses: Vocabulary (mean = 11.5, S.D. = 3.5); Similarities (mean = 10.8, S.D. = 3.7); Arithmetic (mean = 10.5, S.D. = 3.8); Digit Span (mean = 9.8, S.D. = 3.5); Information (mean = 11.1, S.D. = 2.8); Comprehension (mean = 11.6, S.D. = 3.7); Picture Completion (mean = 9.4, S.D. = 3.3); Digit Symbol Coding (mean = 8.9, S.D. = 3.4); Block Design (mean = 9.9, S.D. = 3.5); Matrix Reasoning (mean = 10.9, S.D. = 3.4); and, Picture Arrangement (mean = 9.7, S.D. = 3.3). For this sample, the full form VIQ (mean = 105.9; S.D. = 19.5; 95% CI = ), PIQ (mean = 99.2; S.D. = 19.0; 95% CI = ) and FSIQ (mean = 103.6; S.D. = 19.8; 95% CI = ) scores were calculated. Short form VIQ, PIQ and FSIQ scores are presented in Table 2. The estimated VIQ scores using the seven-subtest version suggested by Paolo and Ryan (1993) and Sattler (2001) was significantly lower than the full VIQ score [F(1, 42) = 9.28, P =.004]. The other short form estimates of VIQ did not differ significantly from the full form VIQ score at P <.01. For PIQ scores, the seven-subtest versions from Ward (1990) [F(1, 42) = 9.42, P =.004] and Paolo and Ryan (1993) [F(1, 42) = 14.06, P <.001] were significantly lower than the mean full form PIQ score. The five-subtest [F(1, 42) = 11.49, P =.002], four subtest [F(1, 42) = 11.15, P =.002] and two-subtest versions [F(1, 42) = 26.01, P <.001] were all significantly higher than the full form PIQ score. The other short form PIQ scores did not differ significantly from the full form PIQ score at P <.01. Regarding short form FSIQ scores, the seven-subtest versions from Ward (1990) [F(1, 42) = 14.71, P <.001] and Paolo and Ryan (1993) [F(1, 42) = 22.77, P <.001] were both significantly lower than the full form FSIQ score, whereas, the four-subtest [F(1, 42) = 17.06, P <.001] and two-subtest [F(1, 42) = 20.91, P <.001] FSIQ scores were significantly higher than the full form FSIQ score. The other short form FSIQ scores did not differ significantly from the full form FSIQ score at P <.01 and are presented in Table 2. Pearson correlations between the full form and short form VIQ, PIQ and FSIQ scores are also presented in Table 2. All correlations were significant at P <.01. Correlations between the short and full form VIQ scores ranged from.89 for Sattler s (2001) two-subtest version to.98 for Ward s (1990) seven-subtest version. Correlations between short and full form PIQ scores ranged from.80 for the three-subtest version to.97 for Ward s seven-subtest version. And finally, correlations between short and full form FSIQ scores ranged from.93 (two-subtest version) to.99 (Ward s seven-subtest version). The percentage of abbreviated scores falling within ±2 S.E.M.s or the same classification range is presented in Table 3. Seven-subtest versions from Ward (1990), Paolo and Ryan (1993), and Sattler (2001) performed very similar, with the percentage of estimated IQ scores within ±2 S.E.M.s ranging from 83 to 85% for VIQ, 83 to 90% for PIQ, and 72 to 85% for

6 Table 2 Mean verbal, performance and full scale IQ scores using the full WAIS-III and eight short form versions in a geriatric sample with suspected dementia Verbal IQ Performance IQ Full scale IQ Mean (S.D.) F (P) a r b Mean (S.D.) F (P) a r b Mean (S.D.) F (P) a r b WAIS-III (19.5) 99.2 (19.0) (19.8) Ward (19.1) 5.82 (.020) * (19.5) 9.42 (.004) ** (19.9) (.001) **.99 Paolo/Ryan (19.4) 9.28 (.004) ** (19.3) (.001) ** (20.1) (.001) **.98 Sattler (19.4) 9.28 (.004) ** (20.3) 0.08 (.780) (20.5) 4.82 (.034) *.98 Sattler (20.1) 2.41 (.129) (20.9) 4.82 (.034) * (21.0) 6.74 (.013) *.98 Sattler (19.8) 0.94 (.339) (21.9) (.002) ** (21.7) 6.45 (.015) *.97 Sattler (19.5) 5.65 (.022) * (22.9) (.002) ** (21.6) (.001) **.96 Sattler (19.5) 5.65 (.022) * (24.6) 0.12 (.729) (21.8) 3.86 (.057).94 Sattler (23.1) 6.40 (.015) * (24.7) (.001) ** (24.1) (.001) **.93 a F(1, 42). b All Pearson correlations are significant at P <.01. P <.05. P < B.L. Brooks, L.E. Weaver / Archives of Clinical Neuropsychology 20 (2005)

7 B.L. Brooks, L.E. Weaver / Archives of Clinical Neuropsychology 20 (2005) Table 3 Clinical accuracy of verbal, performance and full scale IQ scores using the full WAIS-III and eight short form versions in a geriatric sample with suspected dementia Verbal IQ Performance IQ Full scale IQ ±2 S.E.M. a Same class b ±2 S.E.M. c Same class b ±2 S.E.M. d Same Class b Ward Paolo/Ryan Sattler Sattler Sattler Sattler Sattler Sattler a 2 S.E.M.s for the WAIS-III VIQ = b Percentage of short form scores that remained within the same classification category [e.g., low average, average, high average from Wechsler (1997)] as the full form scores. c 2 S.E.M.s for the WAIS-III PIQ = d 2 S.E.M.s for the WAIS-III FSIQ = FSIQ. Clinical accuracy of scores generally decreased concomitantly with decreasing number of subtests. With the exception of one estimated PIQ score using a six-subtest version (Sattler, 2001), short forms with less than seven subtests fell below the a priori criteria for clinical accuracy (>80% within ±2 S.E.M.). 4. Discussion Assessments of older adults with suspected dementia typically evaluate multiple cognitive domains while considering the patient s stamina for testing. A possible solution to the breadth versus brevity consideration is to employ short forms of tests that provide accurate measurement while reducing the amount of testing time. This study sought to evaluate eight short form versions of the WAIS-III in a clinical population of older adults with suspected dementia. Previous research has generally supported seven-subtest short forms of the WAIS-III as the most clinically accurate (Axelrod et al., 2001; Pilgrim et al., 1999; Ryan & Ward, 1999; Wymer et al., 2003). The present study also found high clinical accuracy (>80% of estimated with ±2 S.E.M.) scores when using seven-subtest short forms to estimate VIQ, PIQ, and FSIQ scores. With the exception of the estimated PIQ score with the six-subtest version (Sattler, 2001), short-form versions with less than seven-subtests did not meet the a priori level of clinical accuracy. For the clinician, determining which short form to use depends on the purpose for evaluating intellectual functioning. The use of a short form is not recommended for all situations, particularly when intellectual abilities are central to clinical, psychoeducational, or programming decisions (p. 254, Sattler, 2001). Reasons for selecting a short form of the WAIS-III may include: (1) research purposes, (2) screening purposes, (3) a quick check on the patient s mental status, and/or (4) practical reasons such as patient fatigue (Sattler, 2001). Situations

8 1050 B.L. Brooks, L.E. Weaver / Archives of Clinical Neuropsychology 20 (2005) involving research may emphasize brevity and non-significant differences between short and full form scores (i.e., Sattler s three-subtest version). In clinical situations where the use of a short form WAIS-III is deemed appropriate based on practical, economic, or clinical reasons, there is likely to be an emphasis on accuracy of individual short form scores. In this study, only the seven-subtest versions from Ward (1990) and Sattler (2001) were able to estimate more than 80% of scores within our specified range for accuracy. There are some limitations of this study that may reduce the generalizability of the results. First, the small sample size of this study may make it more difficult to generalize these results to other clinics with different base rates of disorders in those geriatric patients referred for neuropsychological assessment. A second limitation is that the sample does not consist of only those with dementia, but also has some participants with depression and without confirmed cognitive decline. Participants without dementia were purposely included, as this sample mix closely represents those referred an outpatient clinic for evaluation of a suspected dementia. A third limitation of this study is that the present sample may be higher functioning than participants in other studies. Although IQ scores fell within the average range for this sample, this may be higher than would be expected for this clinical population. For example, Axelrod (2002) reported on a sample that had subtest mean scores within the Low Average (6.2) to Average (8.2) ranges and IQ scores within the Low Average range on the WAIS-III, while the present study sample had subtest means and IQ scores that were all within the Average range. A fourth limitation involves the method for calculating short forms in this study, which may actually be underestimating IQ scores. One of the purposes of administering a short form is to reduce the test fatigue of geriatric patients; however, this research examined patients who were administered the full 11-subtest WAIS-III and then short form IQ scores were calculated by re-scoring the original protocol. Further research is needed to determine whether administering only the selected subtests has an effect on patient fatigue and estimated IQ scores. This study supports the limited use of short forms of the WAIS-III in evaluations of geriatric patients with suspected dementia when the full form WAIS-III cannot be administered. If a clinician deems it is appropriate to use a short form version of the WAIS-III, then caution should be exercised when choosing which short form best complements the purpose of the assessment. While there are other options for short-form estimates of IQ scores available to clinicians (e.g., WASI), previous research has suggested that abbreviated versions of the WAIS-III obtain higher levels of clinical accuracy than the WASI when estimating WAIS-III IQ scores (Axelrod, 2002). The present research suggests that the highest level of accuracy when estimating WAIS-III IQ scores is achieved with seven-subtest versions. In particular, the seven-subtest versions provided by Ward (1990) and Sattler (2001) met the stringent a priori level of clinical accuracy for estimating all three IQ scores and it is recommended seven be the minimum number of subtests used to estimate IQ scores with geriatric patients with suspected early dementia. Acknowledgement This study was supported by a Mental Health Studentship from the Alberta Heritage Foundation for Medical Research (AHFMR) to the first author. The authors would like to thank Dr.

9 B.L. Brooks, L.E. Weaver / Archives of Clinical Neuropsychology 20 (2005) Charles T. Scialfa at the University of Calgary for his assistance with the statistical analyses and helpful comments regarding the manuscript, as well as Norma Cassini (past director) and Dr. Patricia Jean in the Seniors Health Ambulatory Care program at the Rockyview General Hospital. References American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th ed.). Washington, DC: Author. Axelrod, B. N. (2002). Validity of the Wechsler Abbreviated Scale of Intelligence and other very short forms of estimating intellectual functioning. Assessment, 9, Axelrod, B. N., Ryan, J. J., & Ward, L. C. (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. Himelstein, P. (1957a). A comparison of two methods of estimating full scale IQ from an abbreviated WAIS. Journal of Consulting Psychology, 21, 246. Himelstein, P. (1957b). Evaluation of an abbreviated WAIS in a psychiatric population. Journal of Clinical Psychology, 13, Margolis, R. B., Taylor, J. M., & Greenlief, C. L. (1986). A cross-validation of two short forms of the WAIS-R in a geriatric sample suspected of dementia. Journal of Clinical Psychology, 42, Osato, S. S., Van Gorp, W. G., Kern, R. S., Satz, P., & Steinman, L. (1989). The Satz Mogel short form of the WAIS-R in an elderly, demented population. Psychological Assessment, 1, Paolo, A. M., & Ryan, J. J. (1993). WAIS-R abbreviated forms in the elderly: A comparison of the Satz Mogel with a seven-subtest short form. Psychological Assessment, 5, Pilgrim, B. M., Meyers, J. E., Bayless, J., & Whetstone, M. M. (1999). Validity of the Ward seven-subtest WAIS-III short form in a neuropsychological population. Applied Neuropsychology, 6, Psychological Corporation. (1999). Wechsler Abbreviated Scale of Intelligence (WASI) manual. San Antonio, TX: Author. Randolph, C., Mohr, E., & Chase, T. N. (1993). Assessment of intellectual function in dementing disorders: Validity of WAIS-R short forms for patients with Alzheimer s, Huntington s, and Parkinson s disease. Journal of Clinical and Experimental Neuropsychology, 15, Ryan, J. J., Lopez, S. J., & Werth, T. R. (1998). Administration time estimates for WAIS-III subtests, scales, and short forms in a clinical sample. Journal of Psychoeducational Assessment, 16, Ryan, J. J., & Ward, L. C. (1999). Validity, reliability, and standard errors of measurement for two seven-subtest short forms of the Wechsler Adult Intelligence Scale-III. Psychological Assessment, 11, Sattler, J. M. (2001). Assessment of children. Cognitive applications (4th ed.). San Diego, CA: Author. Satz, P., & Mogel, S. (1962). An abbreviation of the WAIS for clinical use. Journal of Clinical Psychology, 18, Thompson, A. P., LoBello, S. G., Atkinson, L., Chisholm, V., & Ryan, J. J. (2004). Brief intelligence testing in Australia, Canada, the United Kingdom, and the United States. Professional Psychology: Research and Practice, 35, Ward, L. C. (1990). Prediction of verbal, performance, and full scale IQs from seven subtests of the WAIS-R. Journal of Clinical Psychology, 46, Wechsler, D. (1955). Wechsler Adult Intelligence Scale. New York: The Psychological Corporation. Wechsler, D. (1981). Wechsler Adult Intelligence Scale revised edition. San Antonio, TX: The Psychological Corporation. Wechsler, D. (1997). Wechsler Adult Intelligence Scale third edition. San Antonio, TX: The Psychological Corporation. Wymer, J. H., Rayls, K., & Wagner, M. T. (2003). Utility of a clinically derived abbreviated form of the WAIS-III. Archives of Clinical Neuropsychology, 18,