Researchers at Northwestern University found that people were more likely to solve word puzzles with sudden insight when they were amused, having just seen a short comedy routine, due to lowering the brain’s threshold for detecting weaker or more remote connections to solve puzzles.

This and other recent research suggest that the appeal of puzzles goes far deeper than the dopamine-reward rush of finding a solution. The very idea of doing a crossword or a Sudoku puzzle typically shifts the brain into an open, playful state that is itself a pleasing escape.