Some people find joy and mental stimulation in the Sunday Morning crosswords in the newspaper. I like the crosswords, but what I turn to for a cerebral challenge - on the same page as the crossword puzzle - is the cryptoquips. They have always been my favorite.
The most frequently used letters in the English language are E, T, A, O, N and S - in that order. That is a major key in finding the solution to many a cryptogram. Look for double letters and apostrophes and you are half-way to finding your answer.
True story: (No this is not a synopsis for an episode of Encyclopedia Brown. LOL.) A few years ago a friend came to me with a conundrum because he knew of my penchant for cryptograms. Every Wednesday in the preceding weeks he had found encoded messages taped to his front door and it had him perplexed. He gave me the first cryptic message that he found and it came with another slip of paper that turned out to be the key. To quote my favorite detective Sherlock Holmes, "it was elementary" after that. The decoded message was a list of clues leading to the identity of the sender. It wasn't anything sinister. It was an invitation from a group of kids who had a secret paint-ball club.
Crossword puzzles are indeed mentally stimulating, but cryptograms are what keep "the little gray cells" in working order.