Brain Games How we made these tests
This site has three free tests that run in your browser: a reaction time test, a memory game and the Stroop test. Here is how they work, what exactly we measure and what the numbers can’t tell you.
Who makes this site
The site is made by the makers of the Brain Games app for iPhone. We built these free tests and games so anyone can try them in a browser without installing anything. The app is free to download; playing its games requires a subscription. The tests on this site are free and need no sign-up.
Nothing on this site is a medical test.
How we time your answers
In the reaction time test the screen waits a random time between 1.5 and 4 seconds before it turns green, so you can’t learn the rhythm. The clock starts when the page switches the color and is corrected in the next animation frame, the one in which the browser draws the green. Your press is recorded at the moment the mouse button, finger or key goes down, not when you let go.
A press before green counts as “Too soon”: that try starts again and doesn’t count, and the result shows how many early presses there were. If you switch to another tab during a try, the test pauses and that try doesn’t count either.
In the Stroop test each answer is timed from the frame in which the word is drawn. A click or tap counts when you release it, and the 1, 2 and 3 keys count when you press them. If you leave the tab in the middle of a round, the round is shown again and timed from the start.
Every time includes the delay of your screen, mouse, keyboard or touch screen, and some browsers round their clocks a little for privacy. That is why results from different devices can’t be compared directly.
Why we show the median
Five reaction times are rarely alike. One slow try because you blinked can pull an average far up. The median, the middle value of your five tries, is barely moved by one odd try in either direction, so it is what we call your “typical time”. We also show your fastest try, but we don’t treat it as your result: a very fast try can be a lucky guess.
In the Stroop test the typical time is the median of your correct answers only, counted separately for rounds where the word and the color match and rounds where they differ. If a group has fewer than five correct answers, we don’t show a time for it, because a median of two or three answers says very little.
Practice rounds and random order
The Stroop test starts with two practice rounds that don’t count. Then come 10 rounds where the word and the color match and 10 where they differ, mixed in random order. The same word or the same color never appears twice in a row.
The memory game has 10 rounds and five levels, from three squares on a 3×3 grid up to six squares on a 4×4 grid. If you find all the squares, the next round is one level harder; if not, it is one level easier, always within the five levels. One wrong tap in a round is forgiven. You choose how long the squares stay lit: 3, 2 or 1 second.
Where the games come from
The Stroop test is named after John Ridley Stroop, who published his experiments in 1935 in “Studies of interference in serial verbal reactions” (Journal of Experimental Psychology, 18(6), 643–662).
The rounds where the word and the color differ come from a pool of 20 pairs, and each test uses 10 of them. These 20 pairs are the same as in the Stroop game of version 1.2 of the Brain Games app. Our memory game is based on the Memory game of version 1.2 of the app, which shows three squares on a 3×3 grid for one second. The web version adds the levels and the choice of show time. Version 1.2 of the app has no reaction time test, so we made one only for this site.
What stays on your device
The tests run entirely in your browser, and your answers are never sent to us. Nothing is saved unless you press “Keep my results” under a result. After that, this browser keeps your last result of each game, and your best one in the reaction test and the memory game, so you can compare next time.
Best results are compared only with results of the same kind: the same way of pressing in the reaction test and the same show time in the memory game. The Stroop test keeps only your last result, because a “best” there would reward slow answers in the easy rounds. “Clear my results” deletes everything. Details are in our privacy policy.
What these tests can’t tell you
These are short practice exercises, not medical or psychological tests. They don’t diagnose anything, and we don’t publish norms or averages to compare yourself with. Your numbers change with sleep, mood, time of day and the device you use. The fairest comparison is with your own earlier results on the same device, and even then one try is only a rough picture.