Cognitive fitness software companies like Fit Brains and Lumosity are booming businesses. But whether brain games are the remedy for mental dullness and even disease, or mere digital snake oil, is hotly debated…. …”If you are doing brain training for 10 hours a week, that is 10 hours a week you are not doing something else, like exercising, Zach Hambrick, an associate professor of psychology who worked on the Georgia Tech study, told The New Yorker. “It also gives people false hope, especially older adults for whom this is a big concern.”… What cognitive training pretty clearly won’t provide is a silver bullet to fight off brain decay. A healthy social life certainly wouldn’t hurt, and neither would an appreciation for a good book. Even Hurley admits that “physical exercise is perhaps the best-proved method for improving cognitive function in older people.”