One of the finalists in the 2010 Instructional Innovation Award Competition held by the Decision Sciences Institute was a team of university professors pioneering Puzzle-Based Learning to teach critical thinking and problem solving.
The team claims, "Today's marketplace needs skilled graduates capable of solving real problems of innovation in a changing environment." They feel that students "are often constrained to concentrate on textbook questions at the end of each chapter, solved using material discussed earlier in the chapter. This constrained form of 'problem solving' is not sufficient preparation for addressing real-world problems."
The goal of these professors is to teach students to frame and solve unstructured problems using puzzles to explore and encourage critical thinking. This is intended to be a foundation on which other learning and "domain-specific" problem solving is built, a foundation that gives students a general ability to think about any topic, situation, or problem and consider the best way to approach it. As such, it seems to me this foundation should be built as soon as possible. This team is working with college students, as are some twenty universities worldwide (at the time the article was written), and the article says two high schools are experimenting with Puzzle-Based Learning curricula, as well.
I think we can start much earlier. Sharing age-appropriate puzzles with kids and teaching them to enjoy them can begin whenever we and the child are ready. Until kids are about seven years old, they tend to think very literally, so word play may not register, but maybe they can match and manipulate colors and shapes, follow paths and instructions, sequence events, and so on. Kids are amazing thinkers; let's give them challenging puzzles to ponder.
Try not to emphasize getting a right answer. Enjoy the process of solving. Laugh at wrong answers, and then try again. The best way to get kids thinking and puzzling is to make it fun. Some of the university Puzzle-Based Learning classes have waiting lists longer than the class lists. There's a reason for this: puzzles, critical thinking, and problem solving are fun.
Jen Funk Weber: "Fun" is (part of) her middle name!