Participant performance after awakening from REM sleep was not better than participants who stayed awake, which indicates that in REM sleep, there is an alternative (but just as effective) mode of problem solving that differs from the mechanism available while awake. Sleep facilitates insight Participants in a study were asked to translate a string of digits using two simple rules that allowed the string to be reduced to a single digit (number reduction task). Out of three groups of participants (those who slept, those who stayed awake during the day, and those who stayed awake during the night), participants who got eight hours of sleep were two times as likely during retesting to gain insight into a hidden rule built into the task. In a 1993 study at Harvard Medical School, psychologist Deidre Barrett, PhD, asked her students to imagine a problem they were trying to solve before going to sleep. It was found that her students were able to come up with rational solutions to their problems in their dreams. In this study published in Dreaming (Vol. 3, No. 2), 50% of the students that participated reported having dreams that addressed their chosen problems, while 25% came up with solutions in their dreams. Lack of sleep impairs creativity Some participants in a study went 32 hours without sleep while the control participants slept normally. When tested on flexibility and originality on figural and verbal tests, the sleep-deprived participants had severe and persistent impairments in their performance. A study tested 30 undergraduate students from seven different academic institutions, half majoring in art and half majoring in social sciences. Among all the participants, the higher the level of visual creativity, the lower the quality of their sleep was. The researchers also found that the higher the participants' level of verbal creativity, the more hours they slept and the later they went to sleep and woke up. Sleep and Humor Under hypnotic-induced sleep, participants were much more likely to produce paraphrases of jokes that they had heard before and to spontaneously create new jokes (when compared with their performance while awake). Integration of relational memory Recent studies have also shown that sleep not only helps consolidate memory, but also integrates relational memories. In one study, the participants were tested to see if sleep helped in this aspect (Ellenbogen et al., 2007, as cited in Walker, 2009). The subjects of the experiment were