Improving digit span assessment of short-term verbal memory

Abstract

We measured digit span (DS) in two experiments that used computerized presentation of randomized auditory digits with performance-adapted list length adjustment. A new mean span (MS) metric of DS was developed that showed reduced variance, improved test-retest reliability, and higher correlations with the results of other neuropsychological test results when compared to traditional DS measures. The MS metric also enhanced the sensitivity of forward versus backward span comparisons, enabled the development of normative performance criteria with subdigit precision, and elucidated changes in DS performance with age and education level. Computerized stimulus delivery and improved scoring metrics significantly enhance the precision of DS assessments of short-term verbal memory.

Figures

Figure 1

Population distributions of FS scores for TE-ML, ML, and MS for subjects in Experiment 2. Left: FS, Right: BS. For MS the percentages of scores within each 0.5- digit interval are shown.

Figure 2

The population distribution of FS-BS difference scores for TE-ML, ML, and MS metrics In Experiment 2.