Thirty-second interval patterns for WAIS-III Digit Symbol and Symbol Search

For Digit Symbol-Coding (CD) and Symbol Search (SS) we tested the hypothesis that young adults (44 males, 60 females) would start out quickly and demonstrate steady increases in symbols/items completed across each of four 30-s intervals. The average number of CD symbols was 23.19 (S.D. = 3.46) for 0–30 s, 21.11 (S.D. = 3.75) for 30–60 s, 21.98 (S.D. = 3.70) for 60–90 s, and 22.46 (S.D. = 3.55) for 90–120 s. For SS, the average number of items was 11.91 (S.D. = 1.91) for 0–30 s, 9.96 (S.D. = 1.92) for 30–60 s, 9.95 (S.D. = 1.53) for 60–90 s, and 9.98 (S.D. = 2.46) for 90–120 s. The hypothesis was not supported for either subtest. Cluster analysis revealed two CD groups with similar patterns which differed only in level of performance. On SS, cluster analysis identified two groups which differed in level of performance and pattern across the four 30-s intervals.