Symbol Digit Modalities Test (SDMT)
What It Measures
The SDMT is a ninety-second test of how fast someone can process information. A key at the top of the page pairs nine abstract symbols with the digits 1 through 9. Below it, the symbols appear in random order, and the person works through as many as possible, giving the matching number for each.
The score is simply the number of correct substitutions in ninety seconds. Two response modes are available: written, where the person fills in numbers, and oral, where they say them aloud and the examiner records. The oral version removes the motor demand, which matters for anyone with a hand impairment. Norms exist separately for each mode.
Further Reading
Additional Notes
Licensing Notes: Reproduction of the test material — including in journal articles — requires express written permission from WPS. Forms are consumables; the AutoScore form simplifies scoring.
Learn More: Two things make the SDMT unusual among brief cognitive tests. It allows direct comparison of written and spoken responses from the same person, which can separate a motor problem from a processing one. And the manual provides norms broken down by sex and age for children, and by age group and education level for adults — an important detail, since processing speed is strongly affected by both.