You already know that staying physically and mentally active may help stave off dementia, but researchers have found yet another protective trick—having a purpose in life.

Now, I don’t mean having a goal that has a definite end point, such as telling yourself that you’ll run a marathon or write a novel.

For brain protection, having a purpose in life is a little bit different.

What are some examples of “purposes,” and how can you figure out what yours is if you don’t already have one?