Wayne Kirchner published the first demonstration of the N-back test, a task in which participants have to temporarily memorize information from the past to inform them about the present.
The setup runs as follows: the participant is presented with a string of letters (it can be any form of information, but we’ll stick to letters for this example) and is told to state when the letter is repeated. In the simplest form, known as 1-N, the participant should report when they are presented with immediately matching information (such as “A” followed by “A”).
The “1” of 1-N refers to the position of the letter that the participant should attend to – how far back in the list they need to remember. Each letter is presented individually, so the participant has to keep the sequence in their mind to react appropriately to the next presented letter. If they are presented with the following list, they should indicate the letters that are in bold.
B B O L D D I P R R
If the test was changed to 2-N, then the letters to indicate are different (two spaces apart), and shown as below in bold.
L S L D A Q F P E P
This task becomes increasingly difficult as the number of elements to remember increases, and the amount of cognitive processing also increases.