Listen to a random series of spoken language items (numbers, letters, or words) then try to click on them in the same sequence. Repeat until you have a reliable maximim. STM is clasically "7±2" (5 to 9) random items (Miller, 1956). Earlier Jacobson (1887) found that numbers ( x̄=9.3) were better remembered than letters (x̄=7.3).
V.0.95 April 2021