Numbers & Differences
Subtract from the number you can no longer see
The first of the ATSA's two memory games. Numbers from 1 to 9 appear one at a time, two seconds each. From the second number onwards you type the difference between the number on screen and the one before it — which has already gone. The arithmetic is trivial; holding the previous number while a new one is in front of you is not, and that interference is the whole exercise.
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What to expect
- One number on screen at a time, for two seconds, then a short pause.
- Every number after the first asks one question.
- Answers are always positive and always between 1 and 8.
- You type the answer on the keyboard — there is no on-screen pad, as on the real thing.
What it measures
- Short-term memory under interference
- Mental arithmetic at speed
- Keeping pace with a cadence you do not control
Instructions
- 1Compare the number on screen with the PREVIOUS number shown — never with the answer you just typed.
- 25 then 7 is 2. If 4 comes next, that is 7 − 4 = 3, not 4 − 2.
- 3Answer while the number is still on screen; when it goes, the question goes with it.
- 4The real ATSA gives no feedback until the end — this one shows the working after every answer so a misread rule gets fixed on the spot.
Tips
- Rest a finger over the number row before you start — you are typing single digits at speed, and hunting for the key costs more than the subtraction does.
- Say the number to yourself as it appears; a rehearsed number survives the next one arriving, a merely seen one often does not.
- Answer the instant you have it. The pace is fixed, so a slow correct answer and a fast one score the same — but a slow one leaves you still thinking when the next number lands.
- Small differences come up far more often than large ones, so 1, 2 and 3 are worth having under your fingers.
Numbers & Differences
The ATSA opens with a memory task dressed up as arithmetic. You report the difference between the number in front of you and the one before it — while the next one is already on screen.
You have seen, in order: 14, then 9, then 17. The number now showing is 17, and you are asked for the difference from the previous number. What do you answer?