A study of Nuns and Priests showed mental stimulation reduced incidence of dementia over a five year timeframe
A study of London taxi drivers showed that learning and using ‘The Knowledge’ (road routes and addresses) lead to physical growth in the taxi drivers brains
"all things considered, it’s hard not to conclude that brain training has been proven to work –under certain circumstances” from “A Game to Train your Brain” by Graham Lawton New Scientist January 2008
A trial of MindFit against a carefully selected range of computer games showed that both activities improved ability to carry out a range of tasks (i.e. not just to play games) but that those using MindFit did significantly better