Global Mind Tests

Symbol Digit Substitution Test (SDMT)

Match the shown letter to a digit using a changing key. This task targets processing speed, sustained attention, and consistency under time pressure.

Symbol Digit Test

Answer as many items as you can in 60 seconds, and keep a running sum of all digits. At the end, you will enter your total.

Points
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Multiplier
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Correct
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Accuracy
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Median RT
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Sum error
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Item
0
Correct
0
Digits 1–9 then Enter Track the sum
60s
⚠ During the test, keep a running sum of all digits. You will enter it at the end.
 

What is the Symbol Digit Substitution Test?

The Symbol Digit Substitution Test (often shortened to SDMT) is a timed matching task. You use a key (symbol/letter → digit) and respond as fast and accurately as possible. It is widely used as a quick way to sample processing speed and sustained attention.

What your score reflects

  • Speed: how quickly you can read the key and respond.
  • Consistency: fewer slow outliers usually means better focus.
  • Accuracy under time pressure: rushing increases mistakes.

How to use this test for progress tracking

Repeat on the same device and browser. Compare your trend over time in the history panel. If results drop for a few days, it often means fatigue, stress, or distraction rather than a permanent change.

FAQ

Why am I slower on a phone?

Touch input and mobile browser latency can be higher. For fair comparisons, track progress on the same device type.

Should I focus on speed or accuracy?

Both matter. If you push speed too hard, errors rise and your score becomes noisy. A steady pace is usually best.

Is this an IQ test?

No. This is a short performance task. It does not diagnose intelligence or health conditions.

Try also

Reaction Time Test, Memory Test 3×3, N-back Test.

Read more on our Blog. Related article: Average Reaction Time by Age