It's like real life Brain Age!

Ever play Brain Age on Nintendo's DS system? There's an exercise in arithmetic that you play where icons of people, kind of like the universal symbol for "men" used on restroom signs, go in and out of a house in random numbers, and you need to keep track of how many people are "in" the house by adding the random amounts of little men icons that go in while subtracting the amount going out. It sounds easy, but can get feverishly difficult.

While not exactly like that, I found this video of a border patrol agent having a hell of a time keeping track of the people coming out.