Repeated assessment and practice effects of the written Symbol Digit Modalities Test using a short inter-test interval

Abstract

The Symbol Digit Modalities Test (SDMT) isa widely used instrumentto assess information processing speed, attention, visual scanning, and tracking. Considering that repeated evaluations are a common need in neuropsychological assessment routines, we explored test-retest reliability and practice effects of two alternate SDMT forms with a short inter-assessment interval. A total of 123 university students completed the written SDMT version in two different time points separated by a 150-min interval. Half of the participants accomplished the same form in both occasions, while the other half filled different forms. Overall, reasonable test-retest reliabilities were found (r =.70), and the subjects that completed the same form revealed significant practice effects(p