Digit Symbol Substitution Test (DSST)

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The Digit Symbol Substitution Test (DSST) is a paper-and-pencil test presented on a single sheet of paper that requires participants to match symbols to digits according to a key located on the top of the page. In DSST, the participants then copy symbols into spaces below a row of digits, while in an alternative version–Symbol Digit Modalities Test (SDMT) the participants are asked to write the matching digit in spaces below a row of symbols. In both versions, the number of correct matches within the allowed time, usually 120 seconds, constitutes the score.

This is perhaps the most commonly used test in all of neuropsychology, as it’s a valid and sensitive measure of cognitive dysfunction impacted by many domains, but with minimal impact of language, culture and education on the test performance. However, the question of “what it measures” still has no definitive answer. The SDMT responses are an end product of a wide range of cognitive functions, including attention, visuoperceptual functions like scanning, associative learning and working memory.

In our version, the participant is required to match symbols to digits according to a key located at the top of the page. The participant sees 9 symbols along with 9 digits on the top of the screen. At the bottom of the screen, there is a row of symbols. Participant needs to report the digit that corresponds to each symbol by clicking on the correct digit. The row contains 9 randomised symbols and gets refreshed after completion. The participant is required to answer as many as possible in two minutes. The number of correct matches within the allowed time, 120 seconds, constitutes the score.