N-Back Working Memory Test

What it measures

The N-back test measures working memory — your brain's ability to hold a small amount of information in mind and constantly update it. As a stream of letters appears one at a time, you decide whether each letter matches the one shown a set number of steps earlier (for example, 2 steps back in the standard 2-back). It taps the same updating and attention-control processes you use to follow a conversation, do mental arithmetic, or keep track of where you are in a multi-step task.

How it works

Letters appear one at a time, roughly every 2.5 seconds. You press MATCH whenever the current letter is identical to the one that appeared N positions earlier. About a third of the items are true matches. After a short practice round with feedback, you complete a live run of around 22 trials with no feedback. We tally hits (matches you caught), misses (matches you let slip), false alarms (presses on non-matches) and correct rejections, then report your overall accuracy, a signal-detection sensitivity score (d-prime, which separates real discrimination from guessing), and your mean response time on correct hits.

Tips for an accurate result

• 1Watch the screen, not your hands — Keep your eyes on the centre of the panel and let your finger rest on Space. Looking down to find a button costs you matches.
• 2Silently rehearse the recent letters — Many people do better by quietly repeating the last couple of letters in their head, sliding the window forward as each new one appears.
• 3Don't chase a miss — If you think you missed a match, let it go — dwelling on it usually causes you to miss the next one too. Reset and stay with the stream.
• 4Compare like with like — Your number means most when you retest at the same level, time of day and alertness. Track your trend rather than fixating on one run.