Digit Symbol Substitution asks you to match symbols with their corresponding digit. It consists of 9 digit symbols matched with their corresponding numerical digit. At first this seems simple, but the time limit on the test makes it quite challenging. You have a very small amount of time to enter the correct symbol for each digit.
The most obvious application of digit symbol substitution is to memory. The test requires you to remember where each symbol matches a digit. There is also a speed of processing component, since you have a very small amount of time to enter the correct symbol. In the clinical setting, this test is used to test brain injury, especially for athletes suffering concussions.