N tells you which earlier square to compare
At 1-back, compare the current square with the previous one. At 2-back, look two steps back. At 3-back, look three steps back. The first N positions are only for observation.
This is a 2-back example. At step 3, compare with step 1, not step 2. Both are top left, so select Match while step 3 is current.
A recent repeat can still be a non-match
Now the third square is in the center, like the second square. At 2-back that is not enough. The required comparison is still step 1, which was top left, so do not select Match.
A Match on a non-match subtracts a point. Select Match only for the required distance. You can tap Match or press Space; selecting it again before the next position removes that mark.
Which earlier step matters?
The setting is 2-back and the third square is showing now. Compare it with the square two steps earlier.
Try it
At step 3 in this 2-back example, should you select Match?
- Yes, it matches step 1
- No, it differs from step 2
Show the answer
Yes, it matches step 1
Yes. Steps 1 and 3 are both top right. Step 2 is not the comparison for a 2-back decision at step 3.
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Practice N-back test