A friend sent me a soroban for Christmas.
(Pictured: a soroban, reading "5" all the way across because I forgot to reset it before taking the picture.)
The soroban, or "Japanese abacus," is used in several countries (not just Japan) for rapid, accurate calculations. While a lot of schools have abandoned the abacus except in early childhood education, Japan still teaches entire classes on using it.
Watching people speed-math on this thing is truly impressive. Here's a seven year old girl adding 12-digit numbers as fast as they can be read to her. Poke around YouTube, and you'll find other videos of people mathing even faster.
When I told my friend about being obsessed with the abacus (but not allowed to touch it) in first grade, I expected to get a primary school abacus. Instead, I got this. And I'm not sorry, because this is much cooler.
Reasons my dyscalculic brain likes the soroban:
I don't actually have to do mental math.
"Not doing mental math" includes never having to read a number one way but math it the other way. All numbers are inserted and read on the soroban from left to right.
If the beads are moved correctly, the answer is correct.
It's easy to move beads correctly because I can both feel and see whether they are right or not.
Moving beads correctly requires one to have memorized number bonds from 1-5 and 1-10 - especially in subtraction. But even here, I don't have to deal with the symbols for numbers as long as I know what the beads are supposed to look like.
For instance, my brain doesn't have to deal with "10 = 6 - 4." To add 4, I can just see that I don't have enough beads in my ones column, move a 10, and subtract 6 from the ones. I know I'm right without counting if I move the top bead and one bottom bead. Done.
For me, the soroban solves the problem I have with calculators. Calculators still require number symbols (like "4") to make sense - which they do not always do. Sometimes my brain just rejects that input. ("Ensign 9 is not on the Enterprise." "Where did he go?" "Please restate the question.")
The soroban doesn't. I have to know what the beads look and feel like, not what arcane picture humanity's ancestors drew to represent it. That helps me calculate. It helps a lot.
I have no plans to become a speed math wizard on this thing. But it'd be cool if I could reliably do my own taxes with it.
Math With Soroban: A Japanese Abacus by the SAI Speed Math Academy. While there are several other resources online for learning soroban, Math With Soroban is my favorite so far for the clarity of its examples and the pages' worth of example problems available.
Soroban: The Japanese Abacus. Intro lessons from the Japan Society in the UK. (See also the League for Soroban Education in America.)
Soroban Abacus Handbook by David Bernazzani
"Japan's Ancient Secret to Better Cognitive Memory," BBC Reel - video on Japanese soroban classes.