If you want to stay sharp in old age, learning a language could be the best neural workout. When you consider the challenges for the brain, it’s no wonder most of us find learning a language so demanding. We have many different memory systems, and mastering a different tongue requires all of them. That tough mental workout comes with big payoffs, however, as it is arguably the best brain training you can try. Scientists have found that speaking two languages delays dementia for two years. Those who knew three languages, however, were diagnosed six years later than monolinguals, while for those fluent in four or more languages, enjoyed an extra nine years of healthy cognition.