Ayaka Ono, my current Japanese teacher, estimates she's tutored about 600 students over 15 years. A large study published by the science journal Nature Aging in November suggests that speaking multiple languages protects against more rapid brain aging, and that the effect increases with the number of languages.

Speaking two or more languages is believed to help ward off the memory lapses and reduced mental sharpness that come with an aging brain. Is it too late to start?