In one study by Beijamini, Pereira, Cini, and Louzada (2), participants played a video game, but soon reached an impasse and could not proceed. One half of the participants were then given the opportunity to take a 60-min nap whereas the other half stayed awake during that time. Afterwards, participants returned to the video game. The results were impressive: Compared to participants who stayed awake, participants who had slept were twice as likely solve the puzzle in the video game and overcome the obstacle! In another study (3), participants had to solve math puzzles using two simple rules. However, the puzzles could also be solved with a difficult to find short cut of which participants were not aware of. After a practice period, participants either slept or stayed awake during an 8-hr interval. Participants were then given new math puzzles to solve: About 60% of the participants in the sleep condition discovered the hidden short cut, whereas only 23% of participants in the wakefulness condition managed to find it. This is remarkable because at no point in the study were participants told that there was a hidden short cut and yet participants who had slept were twice as likely to spontaneously detect and use it.

Since problem solving requires the restructuring of a problem in novel ways, creativity has been identified as a factor supporting that process. Creative solutions to problems are original, i.e., not many people will come up with the type solution, and relevant, i.e., the proposed strategy is actually a valid solution to the problem. In one study (4), participants took the Remote Associates Test. In this test, participants are presented with three seemingly unrelated words, e.g., Heart / Sixteen / Cookie, and they are asked to come up with a new word that links the three words together (If you want to give it a try, follow this link). Participants in this study first worked on the Remote Associates Test and then completed in an analogy task (e.g., Chips : Salty – Candy : S_ _ _ _ _). The purpose of this analogy task was to activate appropriate words that may become useful when taking the Remote Associated Test again. In the example above, activating the word “Sweet” can help generating it later when trying to find the one word that links “Heart”, “Sixteen” and “Cookie” together. After doing the analogy task, half of the participants took a 90-minute nap whereas the other half stayed awake. Afterwards, all participants retook the Remote Associates Test. It turned out that participants who had slept during the 90-minute interval were particularly successful in using information that they generated during the analogy task to solve items in the Remote Associates Test. In addition, the researchers found that a good amount of Rapid Eye Movement sleep – the sleep phase where dreaming occurs – was crucial for integrating previously encountered information in order to solve problems creatively.