N-back test online: what came two symbols ago?
See how well you hold and update information that keeps changing, second by second: working memory at work, the ability you lean on to follow a conversation, keep directions in mind or juggle numbers.
The scored part takes 2 minutes at most. A tutorial and practice are included, and there is nothing to prepare.
Press “Same” if it matches the symbol two back
- 1
Learn and practice
A short tutorial and 8 practice rounds that count toward nothing.
- 2
40 scored symbols
Press “Same” only on a match; otherwise, let it pass.
- 3
Your results
Speed, accuracy and sensitivity, read against reference ranges.
What is the n-back test?
The n-back test is a working memory task. In this 2-back version, symbols appear one at a time and you press “Same” only when a symbol matches the one shown two before it. It measures working memory updating and continuous monitoring, and also contributes to measuring interference control and sustained attention. It is a digital version of the N-back task that uses symbols.
- Scored part
- 40 trials, up to 3 seconds each
- Practice
- 8 rounds, unscored
- Devices
- Computer, tablet and phone
- You answer with
- One control
Press “Same” only when it matches two back
Each new symbol is compared with the one shown two symbols earlier, not the one just before. Here is what the screen looks like, and what to do in each case.
Press “Same”. The triangle on screen is the same symbol you saw two symbols ago.
Don't press. The diamond doesn't match the triangle two back, so you do nothing and the next symbol simply appears.
Hold back. The circle feels familiar because it was the last symbol, but it isn't the one two back. The task also includes lures: trials that look like a target but are not one.
What happens on every trial
- 1
A symbol appears
In the centre of the screen, for up to 3 seconds. The first two can never be a match.
- 2
Compare it with two back
Keep the last two symbols in mind and drop the older ones.
- 3
Press or let it pass
No right or wrong is shown; the next symbol just appears.
Rule clear? The real thing is faster than it looks.
What the 2-back task measures
This n-back working memory test asks you to hold a short, moving window of information and check each new item against it. Four abilities take part.
Working memory updating
Keeping the newest items in mind while letting the older ones go.
When someone gives you directions and changes a turn halfway through.
Continuous monitoring
Checking every new item against what you are holding, without a break.
Keeping track of whose turn it is in a game while the talk goes on.
Interference control
Not being fooled by something that only looks like the right answer.
Spotting that a familiar-looking name on a list is not the one you need.
Sustained attention
Staying with a steady stream of information from start to finish.
Following a long phone call without losing the thread.
Curious how your working memory handles a moving window?
How to read your n-back result
When the 40 trials end, the task shows your results screen, reading each measure against reference ranges, and offers to sign up so you can follow them over time. These four are the ones to read first.
Hit rate
Out of every match, the share you pressed correctly and in time. 1 means every one. Higher is better.
False alarm rate
Out of every trial that asked you to hold back, the share on which you pressed anyway. 0 means you never did. Lower is better. Presses on lures are counted on their own too, to show how much a resemblance misled you.
Median reaction time
Your typical answer time, in thousandths of a second: half your answers were faster and half slower, and one very slow answer doesn't move it. Lower is faster. The results also show how steady your rhythm was.
Sensitivity (d′), the key measure
Sensitivity, written d′ and read “d-prime”, sets two things side by side: the matches you caught and the times you pressed when you shouldn't have. Catching many and pressing by mistake rarely gives a high value.
Around 0 means no better than guessing; around 3 or more means almost always right. Higher is better. It describes how you did in this session, not who you are.
Source: CogniFit task description.1
Now you know what to look for on your results screen.
The science behind the n-back task
A simple rule with a long history in cognitive testing: show a stream of items and ask, for each one, whether it matches the item n places back.
To answer, you have to keep the last two items in mind while each new one arrives and pushes the oldest out. That constant holding and replacing is why the n-back has become a familiar way to study working memory. The classic description of the paradigm goes back to Kirchner (1958), who used it to study short-term retention of rapidly changing information.2
Research uses the n-back to study working memory, including in brain imaging studies, as the meta-analysis by Owen and colleagues (2005) reviews.3 It has also been compared with other working memory measures, such as in the meta-analysis by Redick and Lindsey (2013) on complex span and n-back measures.4
CogniFit's Same as Two Back uses symbols instead of letters. What is shown, for how long, what counts as an answer and what is measured all follow the published procedure rather than being invented for this version.
How this version is built
- Matches and non-matches are spread through the task rather than run in blocks, so the difference between them is not measured together with tiredness.
- You answer with one control, pressing only when the rule says so: the task measures detection, meaning hits and false alarms, as well as speed.
- The symbols and their order are drawn fresh every time, so you can take it again without meeting the same sequence.
- Quality checks, such as answers too fast to be real or how many trials were usable, decide whether a session can be read at all. They describe the session, not the person.
What it can tell you
How you did in this session: how many matches you caught, how often you pressed by mistake, and how fast and steady you were. Taken again, it lets you compare your own sessions.
What it can't tell you yet
The studies establish the paradigm; they say nothing about this particular version. Work on how well the n-back reflects working memory, such as Kane and colleagues (2007)5 and Jaeggi and colleagues (2010),6 also shows the limits of reading a single score as a measure of one person. What a given score means for a given person needs population data that has not been collected yet. It is not a diagnosis, and study averages describe groups, not any one individual.
Studies cited: Kirchner (1958); Owen et al. (2005); Redick & Lindsey (2013); Kane et al. (2007); Jaeggi et al. (2010). The full references are listed under Sources.
You know where it comes from. Now see how you handle it.
Questions about the n-back test
How long does the n-back test take?
The scored part is 40 symbols, each shown for up to 3 seconds, so 2 minutes at most. Before it come a short tutorial and 8 practice rounds that count toward nothing. You can repeat the tutorial as many times as you like without it affecting any result.
Do I need an account to take it?
No. You take the task and see your results screen at the end. Signing up is optional and lets you keep your results and follow them over time.
Can I take it on my phone?
Yes. It works on a computer, a tablet or a phone, and you answer with a single control.
Will I know whether each answer was right?
Not during the scored part: the next symbol simply appears. Your hits, false alarms and speed are shown together on the results screen at the end.
Can I take the 2-back test again?
Yes. The symbols and their order are drawn fresh every time, so you won't repeat the same sequence.
Is this a diagnosis?
No. It is an informational task that shows how you did in one session against reference ranges. It is not a clinical assessment and says nothing about your health.
Now see what your working memory does with two back
You know the rule, what the task measures and how to read the numbers. The 40 symbols are ready when you are.
Sources
- CogniFit. Same as Two Back (symbol 2-back): task description, procedure and reported measures.
- 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
- Redick, T. S., & Lindsey, D. R. B. (2013). Complex span and n-back measures of working memory: A meta-analysis. Psychonomic Bulletin & Review, 20(6), 1102–1113. https://doi.org/10.3758/s13423-013-0453-9
- Kane, M. J., Conway, A. R. A., Miura, T. K., Colflesh, G. J. H. (2007). Working memory, attention control, and the N-back task: A question of construct validity. Journal of Experimental Psychology: Learning, Memory, and Cognition, 33(3), 615-622. https://doi.org/10.1037/0278-7393.33.3.615
- Jaeggi, S. M., Buschkuehl, M., Perrig, W. J., Meier, B. (2010). The concurrent validity of the N-back task as a working memory measure. Memory, 18(4), 394-412. https://doi.org/10.1080/09658211003702171
This page and the task are for information only. They are not medical advice, do not diagnose any condition and do not replace care from a qualified professional. If you have concerns about your memory or attention, talk to your doctor.
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