The n-back task
Measure how well you can keep updating what you hold in mind as new items keep arriving.
Method
Procedure
- Letters appear one at a time at the centre, each for half a second, with a new letter every 2.5 seconds.
- Round 1 (1-back, 20 letters): press when a letter is the same as the one just before it.
- Round 2 (2-back, 22 letters): press when a letter is the same as the one two letters before it.
- Each round contains 6 matches. Do nothing when a letter does not match.
Responses
- Space
- match
- Touch
- the Match button
Measures
In each round, the proportion of matches you detected (hits) and the proportion of non-matching letters on which you pressed (false alarms). Comparing 1-back with 2-back shows the cost of holding and updating more items in working memory.
Practice
Two short practice runs, one of 1-back and one of 2-back, tell you after each match, and after each press, whether it was right.
Terms
- Working memory: The system that holds a small amount of information in mind for a few seconds while it is used.
- Updating: Replacing the contents of working memory as new items arrive.
- Hit: A press for a letter that was a match.
- False alarm: A press for a letter that was not a match.
- Load: How much must be held in mind at once; it is higher in 2-back than in 1-back.
Experiment
Responses stay in this browser tab. Nothing is stored or sent, and everything is lost when the page is closed or reloaded.
Results
Interpretation
Good performance means many hits and few false alarms. Pressing for every letter would give 100% hits but also 100% false alarms, so the two numbers must be read together. Performance usually falls from 1-back to 2-back, because more letters must be kept in mind and the comparison changes with every letter.
Limitations
Each round has only six matches, so each missed match changes the hit rate by about 17 percentage points. Reaction times are recorded in the data file but not analysed here.
The result comes from one person in one session, on a device whose timing and display are not calibrated. It describes this run, not a stable characteristic of the participant, and a second run could differ by chance alone. Research studies test many participants under controlled conditions and report the average with its variability. The experiment is educational; it is not a test of ability or health.
One row per letter: round, position, letter, whether it was a match, whether you pressed, reaction time and outcome (hit, miss, false alarm or correct rejection). In the file, 1 means yes and 0 means no. The file is created on this device and can be opened in a spreadsheet.
Background
Original findings
Kirchner (1958) introduced this task to study memory for rapidly changing information. Each step back adds to the load: several recent letters must be kept in mind, each new letter compared with the right one, and older letters discarded. Performance usually falls as n increases.
Neural basis
A meta-analysis of 24 brain-imaging studies of the n-back task found consistent activity in the frontal and parietal lobes, including the dorsolateral and ventrolateral prefrontal cortex and the posterior parietal cortex (Owen et al., 2005).
References
- Kirchner, W. K. (1958). Age differences in short-term retention of rapidly changing information. Journal of Experimental Psychology, 55(4), 352–358. https://doi.org/10.1037/h0043688
- Owen, A. M., McMillan, K. M., Laird, A. R., & Bullmore, E. (2005). N-back working memory paradigm: a meta-analysis of normative functional neuroimaging studies. Human Brain Mapping, 25(1), 46–59. https://doi.org/10.1002/hbm.20131
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