Abstract

The traditional method of scoring Digit Span Test is to sum the scores of digits forward (DF) and digits backward (DB). However, several researchers have articulated the need for scoring DF and DB separately and comparing the two. The WAIS-III accepts the view and includes a U.S. norm for the difference between DF and DB. However, no Korean norm for the difference between DF and DB has been published yet. Thus, the aim of the present study was to provide a Korean norm for the difference between DF and DB. A total of 201 Korean normal subjects were administered DF and DB. The effects of age, years of education, or FIQ on the difference between DF and DB were minimal and statistically nonsignificant. Thus, the norm for the difference between DF and DB was constructed regardless of age, years of education, or FIQ. The unit of measurement for the norm was the number of digits forward minus the number of digits backward. The difference of 3 or smaller corresponded to 35.3%ile and may be classified as normal; the difference of 4 corresponded to 16.4%ile and may be classified as borderline; and the difference of 5 or greater corresponded to 6.5%ile and may be classified as abnormal. The DF requires short-term maintenance of information, whereas the DB requires short-term manipulation as well as short-term maintenance of information. Thus, the DF is a short-term memory task, whereas the DB is both a short-term memory task and a working memory task. Viewed in this way, the difference between DF and DB could be used as an index of working memory capacity.