I could have a big-time bias toward believing this headline is true as written. (See my user profile here on Hacker News for more details about my language studies.) But I wonder if the really generalizable finding is simply that adult learners taking on a new challenging learning topic prompt their brains to grow and stay flexible longer. For me, after learning a lot of natural human languages, brushing up and extending my knowledge of mathematics for a career change seemed to provide a fair amount of intellectual growth. Maybe now it's time for me to take up music lessons or an active team sport like soccer. There is always time to learn something new, and there seem to be a lot of benefits from learning almost anything.