The other day I was listening to an interview on National Public Radio with Dean Oshler who has just written a book called From Square One: A Meditation, with Digressions, on Crosswords. During the interview I was surprised to hear Mr. Oshler challenge the widely held belief that regularly doing crossword puzzles is good for your brain fitness and can help stave off Alzheimer’s disease. Oshler’s problem with crossword solving is twofold: first, he believes the clinical data showing an advantage for puzzlers is both weak and only observational (“[The researcher] never said that there was a cause-and-effect relationship. He said there was a correlation. Maybe it just so happens that people who are mentally fit have a tendency to want to do crosswords in the first place”); second, we need variety in our mental exercise (“[Crosswords are] kind of the same activity over and over again. But the Alzheimer’s…