WAIS−IV coding performance of young adults: Transcription patterns and incidental learning procedures

The Digit Symbol-Coding (DS-C) subtest of the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III; Wechsler, 1997) and the Coding subtest (CD) of the Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV; Wechsler, 2008a) are primarily measures of processing speed and clerical efficiency. Both subtests are complex and require attention, concentration, cognitive flexibility, visual scanning, adequate motor coordination, and positive test taking motivation (Joy, Fein, & Kaplan, 2003; Kreiner & Ryan, 2001; Sattler & Ryan, 2009). The DS-C and CD subtests both use keys containing nine numbers, each paired with a different abstract symbol, and a response sheet consisting of boxes with a number in the top part and an empty space in the bottom part. The examinee is required to copy the correct designs under their associated numbers as rapidly as possible within a 120-second time limit. Both editions produce total correct raw scores which are converted into scaled scores with a mean of 10 and a standard deviation of 3. A validity study reported in the WAIS-IV: Technical and interpretive manual (Wechsler, 2008b) indicates that when both the WAIS-IV and WAIS-III (Wechsler, 1997) were administered to the same individuals, DS-C and CD subtest scores were highly correlated regardless of whether the examinees were healthy controls (n = 240; r = .85), persons with borderline intelligence (n = 24; r = .62), or individuals with mild intellectual disability (n = 25; r = .87). Also, in the normal and mild disability samples the mean scaled scores on CD were lower than those on DS-C by an average of -0.2 and -0.4 points, respectively. Conversely, individuals with borderline intelligence scored higher on CD by an average of +0.1 points than they did on the DS-C subtest. The findings of large correlations between DS-Coding and CD are consistent with previous investigations that compared the WAIS-III DS-C subtest with the Wechsler Adult Intelligence Scale-Revised (WAIS-R; Wechsler, 1981) Digit Symbol subtest and those that compared the WAIS-R Digit Symbol subtest with its counterpart in the Wechsler Adult Intelligence Scale (WAIS; Wechsler, 1955). However, the fact that individuals with borderline intelligence earned a higher mean score on CD than on DS-Coding stands as an atypical finding. Previous studies have consistently reported that mean scaled scores on the revised subtest were below, and in many cases substantially below, those on the older version of the task (Ryan, Nowak, & Geisser, 1987; Wechsler, 2002). To increase the clinical yield of the WAIS-R Digit Symbol and WAIS-III DS-Coding subtests, it was suggested that progress be recorded at the end of each 30-second time interval as the subtest progresses (Kaplan, Fein, Morris, & Delis, 1991; Lichtenberger & Kaufman, 2009). Analyzing performance over quarters may yield qualitative information that would be useful in understanding the examinee. Steady improvement over the 30-second intervals may suggest a need to "warm up" to the task (Ashendorf & Reynolds, 2013; Kaplan et al., 1991) followed by the rapid learning of the number-symbol pairs (Nicholson & Alcorn, 1994). When this pattern emerges the need to reference the key is reduced or even eliminated and the number of symbols copied over each 30-second interval shows a steady increase. Conversely, the individual may rely primarily on psychomotor speed to complete the task (Salthouse, 1978) with limited input from memory of the symbols that develops over time (Joy, Fein, & Kaplan, 2003; Kreiner & Ryan, 2001). A second modification of the Digit Symbol and DS-C sub tests was designed to enhance clinical utility and elucidate, at least in part, the contribution of learning to subtest performance via the administration of incidental recall trials immediately following completion of the task. These procedures have been used successfully to discriminate among healthy elderly, depressed elderly, and persons with mild dementia of the Alzheimer's type (Hart, Kwentus, Wade, & Hamer, 1987) as well as between groups of patients diagnosed with either Alzheimer's disease or Parkinson's disease (Demakis, Sawyer, Fritz, & Sweet, 2001). …