The Guardian reports on a Japanese contest called flash anzan, where the contestants add numbers in their head by imagining an abacus.
[A] million Japanese children every year learn the abacus, which they call soroban.
The high point of the abacus calendar is the All Japan Soroban Championship, which took place earlier this year in Kyoto.
And the high point of the championship is the category called "Flash Anzan" – which does not require an abacus at all.
Or rather, it requires contestants to use the mental image of an abacus. Since when you get very good at the abacus it is possible to calculate simply by imagining one.
In Flash Anzan, 15 numbers are flashed consecutively on a giant screen. Each number is between 100 and 999. The challenge is to add them up.
Simple, right? Except the numbers are flashed so fast you can barely read them.
I was at this year's championship to see Takeo Sasano, a school clerk in his 30s, break his own world record: he got the correct answer when the numbers were flashed in 1.70 seconds. In the clip below, taken shortly before, the 15 numbers flash in 1.85 seconds. The speed is so fast I doubt you can even read one of the numbers.