The calculator is a mechanical tool and it doesn’t require a brainy person to use it.  No mental process is required, and no genius ability is required for computation.  In short, there is no brain activity involved.

Children who use abacus are required to use massive brain functions and mental abilities to derive an answer, and in the process there is a coordinated effort of left brain’s logical function with concentration, memory and imaging function of right brain.  This will allow overall human brain to be developed in a better and fitter way.

Like the body that requires exercise to be fit, so does the brain.  Research has shown that effective mental arithmetic training does help to prevent or decelerate senile dementia.