Age Effects on Wechsler Adult Intelligence Scale-III Subtests

Archives of Clinical Neuropsychology, Vol. 15, No. 4, pp. 311–317, 2000 Printed in the USA. All rights reserved 0887-6177/00 $–see front matter PII S0887-6177(99)00019-0 Age Effects on Wechsler Adult Intelligence Scale-III Subtests Joseph J. Ryan Dwight D. Eisenhower Veterans Affairs Medical Center Jerome M. Sattler San Diego State University Shane J. Lopez University of Kansas This investigation extended work on the Wechsler Adult Intelligence Scaled-Revised (WAIS-R) to the WAIS-III by determining how allotments of scaled-score points change with age, and to evaluate WAIS-III performance in terms of the Horn-Cattell constructs of crystallized and fluid intelligence. The age norms for the 14 individual WAIS-III subtests indicate that additional scaled-score points are awarded primarily to the Letter-Number Sequencing subtest of the Verbal Scale and to the seven Performance Scale subtests at ages 45 to 89 years for the same performance as individuals in the 20- to 34-year-old reference group. Subtests that measure speed of information processing showed more of a decline than subtests that measure verbal processing. Results are consistent with the view that measures of fluid intelligence show more of a decline with advancing age than do measures of crystallized intelligence. Published by Elsevier Science Ltd Keywords: age, intelligence, WAIS-III The differential effects of age on psychometric intelligence have been documented (Kaufman, 1990; Matarazzo, 1972). Analyses of the Wechsler-Bellevue Scale (WB-I; Wechsler, 1939), Wechsler Adult Intelligence Scale (WAIS; Wechsler, 1955), and Wechsler Adult Intelligence Scale-Revised (WAIS-R; Wechsler, 1981) standardization data demonstrated that declines were more striking on the Performance Scale than on the Verbal Scale. Sattler (1982) also analyzed data from the standardization sample of the WAIS-R and showed that to maintain the same IQ values across the lifespan additional scaled-score points must be awarded with increasing age. This was more apparent for the Performance Scale subtests than for the Verbal Scale subtests. These findings are consis- Address correspondence to: Joseph J. Ryan, PhD, Chair, Department of Psychology, 117 Lovinger Building, Central Missouri State University, Warrensburg, MO 64093. E-mail: 311 312 J. J. Ryan et al. tent with the theory of fluid and crystallized intelligence in that Performance or fluid abilities change more over the lifespan than Verbal or crystallized abilities. This investigation sought to extend Sattler’s (1982) work on the WAIS-R to the WAIS-III (Wechsler, 1997) by determining how allotment of scaled-score points for the same level of achievement changes as a function of age. A second purpose was to evaluate age effects on WAIS-III performance in terms of the Horn-Cattell constructs of crystallized and fluid intelligence (Horn, 1985). METHOD The WAIS-III standardization sample is divided into 13 age groups, each consisting of 200 participants (100 male, 100 female), with the exception of age ranges 65 to 69 years (90 males, 110 females), 70 to 74 years (88 males, 112 females), 75 to 79 years (83 males, 117 females), 80 to 84 years (54 males, 96 females), and 85 to 89 years (32 males, 68 females), where females outnumber males. Stratification was based on 1995 U.S. Census data and included age, gender, race/ethnicity, educational level, and geographic region of residence. The norms on the WAIS-III are in increments of 2 years for individuals in the age range 16 to 19 years, 5 years for those 20 to 34 years, 10 years for persons 35 to 64 years, and 5 years for individuals 65 to 89 years. Table A.1 in the WAIS-III Administration and Scoring Manual (Wechsler, 1997) gives scaled-score points for raw scores on the 14 subtests by age. The following procedure was used to determine age changes in the allotment of scaled-score points. The raw score for each subtest that equaled the average scaled score (M ⫽ 10) in the reference group of persons 20 to 34 years of age was found in Table A.2 in the WAIS-III manual (Wechsler, 1997). When a range of raw scores was given, the lower limit of the range was used. From these raw scores, scaled scores from Table A.1 were then obtained for the 13 age groups (i.e., 16–17 years, 18–19 years, 20–24 years, 25– 29 years, 30–34 years, 35–44 years, 45–54 years, 55–64 years, 65–69 years, 70–74 years, 75–79 years, 80–84 years, and 85–89 years). By subtracting 10 from each of these scaled scores, the number of points above or below the average of the 20- to 34-year reference group was determined for each subtest. This method reveals the level of performance for each of the age groups that corresponds to average performance in the reference group and allows for a gross evaluation of how well the WAIS-III data conform with expectations based on the Horn-Cattell theory of intelligence. RESULTS AND DISCUSSION WAIS-III Performance Across the Lifespan Table 1 indicates that there were few differences in the verbal abilities of the younger and older age groups. The Information subtest shows the most stability across the age range. For example, a raw score of 14 yields a scaled score of 10 in the reference group and also yields a scaled score of 10 for persons 85 to 89 years old. Conversely, the LetterNumber Sequencing subtest displays the greatest difference across age groups among the Verbal subtests. A raw score of 11 produced a scaled score of 10 in the reference group, but at ages 85 to 89 years, this same raw score yields a scaled score of 15. The five scaled-score points awarded at ages 85 to 89 years for a raw score of 11 changes the percentile for the raw score from the 50th to the 95th.  0 0 0 0 0 0 0 0 ⫺1 0 0 0 ⫺1 0 0 0 0 ⫺1 0 0 0 18–19 1 0 0 0 0 1 0 16–17 0 ⫺1 0 0 0 0 0 0 0 0 0 0 0 0 20–24 0 0 0 0 0 0 0 0 0 0 0 0 0 0 25–29 0 0 0 0 0 0 0 ⫺1 ⫺1 ⫺1 0 ⫺1 ⫺1 0 30–34 0 0 0 1 0 0 0 ⫺1 ⫺1 ⫺1 0 ⫺1 ⫺1 0 35–44 0 1 1 1 1 1 1 ⫺2 ⫺1 ⫺1 0 ⫺2 ⫺2 1 45–54 Note. Negative values indicate performance that exceeds the reference group of persons 20 to 34 years. WAIS-III = Wechsler Adult Intelligence Scale-III. Verbal Vocabulary Similarities Arithmetic Digit Span Information Comprehension Letter-Number Seq Performance Picture Comp Digit Symbol Block Design Matrix Reason Picture Arrang Symbol Search Object Assembly Subtests Age Range 1 3 2 2 2 2 2 ⫺1 0 ⫺1 1 ⫺1 ⫺1 2 55–64 1 4 3 3 3 3 3 ⫺1 1 0 1 ⫺1 ⫺1 2 65–69 2 5 4 4 4 5 4 ⫺1 1 0 1 ⫺1 ⫺1 3 70–74 3 6 5 5 5 6 6 ⫺1 1 0 2 ⫺1 0 4 75–79 TABLE 1 Additional Scaled-Score Points by Age Awarded to WAIS-III Subtests When the Reference Group Receives a Scaled Score of 10 4 7 5 5 6 8 6 1 2 1 2 0 1 4 80–84 6 8 6 6 6 9 7 1 3 2 3 0 1 5 85–89 Age Effects on the WAIS-III 313 314 J. J. Ryan et al. Table 1 shows that there are differences in nonverbal ability between younger and older adults. Subtests that assess speed of information processing show the greatest difference as one moves (...truncated)