Try this: Instead of simply following the plotline of a book or TV show, come up with insights or take-home messages that you can apply to your life. Everything can be mined: Downton Abbey for money lessons, Jane Austen for life advice, anything. When study participants pushed their minds this way, they showed cognitive gains after just six hours of training and significant structural changes in the brain's white matter connections in six to 12 weeks. "Mental weight-lifting" is not like physical exercise, Kirkland says. You must do this throughout your day, as often as possible, continually.