At baseline, the WISC-R/WISC-III included the Digit Span subtest. The forward component of digit span was used to assess working memory maintenance. Digit span forward is administered by orally presenting a series of numbers that the examinee has to verbally repeat. The longest series of digits that one could recall was used as the primary variable of interest. The WISC-R digit span forward section included pairs of seven items that ranged from 3 to 9 digits in length. The WISC-III digit span forward retained all seven WISC-R forward item pairs; however, a 2-digit series was added at the beginning (i.e. eight items that ranged from 2 to 9 digits in length) (Wechsler, 1991). Since no child had a longest digit span forward of two, this difference did not affect our measure of working memory maintenance.
