What this test measures
The Trail Making Test is one of the most widely used tasks in neuropsychology, and its appeal is that it is almost embarrassingly simple: join the dots in order, as fast as you can. What makes it informative is the second half.
Part A is numbers only. To do it quickly you need to scan a cluttered field, find the next target and move to it — visual search plus motor speed, and not much else.
Part B keeps all of that and adds a demand: two sequences are running at once, and you have to alternate between them while remembering where you are in each. Everything that made Part A hard is still there, with switching stacked on top.
Why running both parts is the whole point
If you only had Part B, a fast time could mean you are good at switching — or just that you have quick eyes and a quick finger. Because both parts share the same searching and the same tapping, subtracting A from B removes most of that shared load, and what is left is much closer to the cost of the switching itself.
This is not a folk theory. A study examining what the test actually taps concluded that Part A reflects mainly visuoperceptual ability, Part B mainly working memory with a secondary contribution from task-switching, and that the B-minus-A difference provides “a relatively pure indicator of executive control abilities” by stripping out the visuoperceptual and working-memory demands the two parts have in common.
Your headline number is the total time for both parts, because that is the one people want. Underneath it you get Part A, Part B and the difference between them. If you only look at one thing after your second or third attempt, look at the difference.
How to read your result
- Total time is your headline, and the easiest thing to improve — mostly by getting familiar with the format.
- Part B is always slower than Part A. That is expected and not a bad sign. A difference of a few seconds means switching is cheap for you today; a large one means it is not.
- Errors show up as time, not as a separate score. A run with several wrong taps is slower for a reason worth noticing.
- Your first attempt is the worst one you will have. Everyone speeds up once they stop hunting for the rule.
How this version differs from the clinical test
This matters, because the Trail Making Test is a real clinical instrument and it would be easy to imply more than a web page can deliver.
- Paper versus screen. The clinical test is a pencil drawing a continuous line across a printed A4 sheet. Here you tap, and your finger travels a different distance on a phone than on a laptop.
- Fixed layout versus generated layout. The printed test uses one standardised arrangement that every participant sees. This page generates a fresh layout each time, which is fairer for repeat attempts but breaks comparability with published norms.
- Examiner versus no examiner. On paper, an examiner catches an error the instant it happens and tells you to go back. Here a wrong tap simply does not register, which costs you the same kind of thing — time — but not in the same way.
The consequence is straightforward: do not read your number against published normative tables. Read it against your own previous attempts on the same device.
Where the test comes from
The task first appeared in the United States Army Individual Test Battery in the 1940s and was brought into clinical neuropsychology by Ralph Reitan, whose 1958 paper proposed it as an indicator of organic brain damage. It has been in continuous use ever since, which is why normative data are unusually thorough — Tombaugh's widely cited tables stratify performance by both age and education, because both of them move the times a long way.
That last detail is worth sitting with. If age and education shift the expected times substantially, then a single number with no context — the kind most websites hand you — is not telling you what it appears to be telling you.
Questions people ask
What is a good Trail Making Test time?
Published norms exist, stratified by age and education, but they were collected with pencil and paper on one fixed printed layout. This version uses taps on a freshly generated layout on a screen of unknown size, so those tables do not apply to it.
Age and education both move the numbers substantially, which is another reason a single web result means little on its own. Compare your own attempts on the same device instead.
Why does the test have two parts?
Part A asks only for visual search and a fast finger. Part B adds the requirement to hold two sequences at once and alternate between them.
Running both lets you subtract one from the other, which is the whole point: what is left over is much closer to the cost of switching than either part is on its own.
What does the B minus A score mean?
It is the extra time Part B cost you compared with Part A. Because both parts share the same visual search and the same tapping, subtracting removes most of that shared load.
A study of the test's construct validity concluded that the B minus A difference gives a relatively pure indicator of executive control, while Part A reflects mainly visuoperceptual ability and Part B mainly working memory with a task-switching contribution.
Do mistakes count against me?
There is no separate penalty, but a wrong tap does not advance the trail and the clock keeps running, so errors cost you time.
That mirrors how the test is administered on paper, where the examiner points out the mistake and the participant carries on while the stopwatch runs.
Is this the same as the clinical Trail Making Test?
No. It follows the same structure — 25 targets per part, numbers only in A, numbers alternating with letters in B, with a short practice before each — but the clinical test is pencil and paper on one standardised printed layout administered by a trained examiner.
This is taps on a randomly generated layout on your own screen. Treat it as a demonstration of the task, not as an administration of the test.
References
- Sánchez-Cubillo, I., Periáñez, J. A., Adrover-Roig, D., Rodríguez-Sánchez, J. M., Ríos-Lago, M., Tirapu, J., & Barceló, F. (2009). Construct validity of the Trail Making Test: role of task-switching, working memory, inhibition/interference control, and visuomotor abilities. Journal of the International Neuropsychological Society, 15(3), 438–450. PubMed
- Tombaugh, T. N. (2004). Trail Making Test A and B: normative data stratified by age and education. Archives of Clinical Neuropsychology, 19(2), 203–214. PubMed
- Reitan, R. M. (1958). Validity of the Trail Making Test as an indicator of organic brain damage. Perceptual and Motor Skills, 8, 271–276.