It was noted that one thing many scientists (and others) have in common is a love of puzzles. They require critical thinking skills and many require a scientific inquiry type approach to solve. We decided to see if encouraging our students to attempt a number of puzzles throughout the semester, for extra credit, would enhance their critical thinking skills or at least encourage them to start attempting more puzzles which may be have beneficial in the long run. Each student is supplied with increasingly difficult Suduko puzzles throughout the semester, with completion being rewarded with a small amount of extra credit.
After several semesters of giving out the puzzles in class, I realized that only the students who already knew how to do the puzzles were the ones completing more than one puzzle. Those that the assignment were aimed at tended to get frustrated by the puzzles and stop attempting them after the first one, I also learned that many students discovered online Suduko solvers to provide the answers.