According to one study, it appears that the kids can only see three or four columns of an abacus in their minds at one time. However, that didn’t account for the more complex calculations performed by expert students or the fact that most abaci have at least 15 columns of beads. The researchers also discovered that expert mental abacus users were less efficient if they listened to a story or tapped their fingers on furniture while performing their calculations. But they still did much better than college kids without this specialized training. The college students were almost completely unable to perform the calculations if they heard a story at the same time.