Those of us who are entering old age frequently read books or online articles about ways to enhance our mental agility, to keep our minds nimble and quick. Some people follow special diets, believing that certain foods or supplemental vitamins can strengthen our powers of reason and thought. Others exercise at the gym or take long walks through their neighborhood as a means to keep the lights burning in the attic. Some experts tell us that playing cards or board games, or matching wits with Sudoku or crossword puzzles help feed our powers of cognition. A few of the elderly people I’ve known believe that communication—conversations with family and friends, reading, writing letters and emails—contributes to the care and preservation of the mind. Other men and women find that work helps to keep them young. Clint Eastwood, age 91, just directed and starred in another Western, “Cry Macho,” and the …