Dreams have arguably been a source of creative insight for millennia. The specific assertion that dreams during rapid eye movement (REM) sleep promote creative problem-solving, however, has only anecdotal support, lacking strong empirical support from rigorous studies. Experimental manipulations of dream content have been confounded by waking components, such that any boost in creative problem-solving could be attributable to waking cognition rather than sleep cognition. Likewise, correlational evidence cannot unequivocally establish that dreams cause insights. ⁠ ⁠ Evidence that memory reactivation during sleep promotes creative problem-solving is also insufficient for implicating dreaming per se. Better methods for directly manipulating REM-sleep dreaming are needed. Here, we studied individuals who frequently have lucid dreams—realizing they are dreaming while still asleep. Participants slept after failing to solve several puzzles that had unique soundtracks, and they were instructed...