Digit span is a great working memory test, one that I'm pretty abysmal at, especially the version where you have numbers and letters and have to recite back the answer with letters/numbers in reverse alphabetical/chronological order. If you have trouble manipulating and remembering information in short-term memory and/or have difficulty understanding multiple instructions at one time, it's likely you have executive functioning/working memory deficits.
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Helinger: Now, what do you see, John?
Nash: Recognition...
Helinger: Well, try seeing accomplishment!
Nash: Is there a difference?