Recent studies have shown that the abacus method of mental calculation is effective in the development of the right brain. At first, this idea was only a hypothesis, but the recent development of hightech machinery has helped provide tangible research data. In this section, we will present information provided by researchers who study the effects of abacus training.
The first effect is improvement of numerical memory.
The second is improvement of memory in spatial arrangement.
The third is progress in solving general mathematical problems taught in elementary school, including the four fundamental arithmetic calculations and word problems.
More Links 
Abacus & Right Brain Development 

The Ripple Effects and the Future Prospects of Abacus Learning. Ms. Shizuko Amaiwa 

What Abacus Education Ought to Be for the Development of the Right Brain. Dr. Toshio Hayashi Doctor of Engineering. Professor, Osaka Prefecture University. Director, Research Institute for Advanced Science and Technology. August 24, 2000 

Becoming fond of Numbers and Math! Ms. Kimiko Kawano 