Wechsler Intelligence Scale for Children - Memory for Digit Span

The Memory for Digit Span assessment, a component of the Wechsler Intelligence Scales for Children-Revised (WISC-R), is a measure of short-term memory for children aged seven and over (Wechsler 1974). The WISC-R is one of the best normed and most highly respected measures of child intelligence (although it should be noted that the Digit Span component is one of the two parts of the Wechsler scale not used in establishing IQ tables).

Description of the Memory for Digit Span

There are two parts to the Memory for Digit Span assessment: Digits Forward and Digits Backward. Each tap distinct but interdependent cognitive functions. Digits Forward primarily taps short-term auditory memory while Digits Backward measures the child's ability to manipulate verbal information while in temporary storage. In Digits Forward, the child listens to and repeats a sequence of numbers spoken aloud by the interviewer. In Digits Backward, the child listens to a sequence of numbers and repeats them in reverse order. In both parts, the length of each sequence of numbers increases as the child responds correctly. The precise instructions and items used in this assessment can be found in the Memory for Digit Span section of the NLSY79 Child Supplement, available on the Questionnaires page.

Administration of the Memory for Digit Span

The child is instructed to repeat a series of numbers (with increasing numbers of digits) forward and a different series of digits in reverse order.  Each correct response is worth one point; with a maximum of 14 points for each subscore series and hence 28 for the total score. The forward digit sequence is completed prior to beginning the backward digit sequence. However, entry into the reverse sequence is not contingent on successful entry or completion of the forward sequence. Prior to 2002, where appropriate, this assessment was administered in Spanish.

Age Eligibility for the Memory for Digit Span

Starting in 1996, this assessment is administered to all children age seven through 11 years. In prior rounds, it was administered to children ages seven and over who had not previously received the assessment, and to all ten and eleven year olds (see Table 4 in the Child Assessments--Introduction).

Norms for the Memory for Digit Span

Whereas the normed scores for the other assessments are based on a mean of 100 and a standard deviation of 15, the Digit Span assessment is normed against a distribution that has a mean of 10 and a standard deviation of 3. Norms are only available for the total score. The norms are published in the WISC manual (Wechsler 1974: 118-150). 

Completion rates for the Memory for Digit Span

The overall completion rate for Digit Span in the most recent survey rounds is between 79 and 86 percent, a slight drop from previous rounds. This overall level of completion generally holds across all three race/ethnicity categories in the current survey year (see Table 6 in the Child Assessments--Introduction section).

Validity and Reliability for the Memory for Digit Span

In multivariate analyses carried out with the 1992 data that controlled for a wide range of demographic and socio-economic antecedents, the scores of black and Hispanic children were not below those of non-Hispanic, non-black children on either the forward or backward assessment (The NLSY Children, 1992: Description and Evaluation). In the same analyses, it was also found that the two 1986 Digit Span subscores, in particular the reverse order "digit backwards" assessment, were useful independent predictors of all of the PIAT scores for older children in 1992. Users who want more detailed information about the reliability and validity of these assessments and a brief discussion of other literature about studies that have used these assessments should consult the NLSY Child Handbook: 1986-1990 and The NLSY Children, 1992: Description and Evaluation, available on the Research/Technical Reports page.

Digit Span Scores in the Database

This assessment generates three "raw" scores (one for each of the two subscales and one for the total score) along with one overall age-appropriate normed (standard) score. The complete listing of question names for assessment scores for the most recent survey round can be found in Table 1 in the Child Assessments--Introduction section.