How many digits can you hold in your short-term memory?
This test uses the classic digit span paradigm from cognitive psychology: hold a growing sequence of digits in mind and reproduce it. Average adults manage about 7 ± 2 digits — the famous "magical number" described by George Miller in 1956. Working memory is one of the strongest single predictors of reasoning ability, reading comprehension and academic performance.
Spans of 5-6 are common, 7-8 above average, and 9+ exceptional. Backward span (reproducing in reverse) is typically two digits shorter and taxes executive control harder.
Can working memory be improved? Training improves performance on the trained task (chunking digits into groups is a powerful strategy), but transfer to general intelligence is limited according to meta-analyses. Sleep and stress management reliably affect day-to-day capacity.
Why digits? They are culture-fair within literate populations, easily randomized, and directly comparable to decades of published research.