REM, not incubation, improves creativity by priming associative networks

Abstract

The hypothesized role of rapid eye movement (REM) sleep, which is rich in dreams, in the formation of new associations, has remained anecdotal. We examined the role of REM on creative problem solving, with the Remote Associates Test (RAT). Using a nap paradigm, we manipulated various conditions of prior exposure to elements of a creative problem. Compared with quiet rest and non-REM sleep, REM enhanced the formation of associative networks and the integration of unassociated information. Furthermore, these REM sleep benefits were not the result of an improved memory for the primed items. This study shows that compared with quiet rest and non-REM sleep, REM enhances the integration of unassociated information for creative problem solving, a process, we hypothesize, that is facilitated by cholinergic and noradrenergic neuromodulation during REM sleep.

Fig. 1.

Experimental design. Subjects were administered the creative problem solving test in the morning and then a word analogy priming task. After an intervening polysomnographically recorded sleep or quiet rest period, subjects were tested on the three prior exposure conditions: repeated exposure (white box), primed exposure (gray box), or no exposure (black box). Memory tests for the analogy solutions followed.

Fig. 2.

Incubation-dependent improvements in performance are independent of sleep. NREM sleep, REM sleep, and quiet rest similarly improved performance on the repeat items compared with the morning baseline performance (CI 95%, 6.5–38.3%; CI 95%, 10.6–50.2%; and CI 95%, 2.4–71.0% for the REM, NREM, and rest groups, respectively).

Fig. 3.

REM sleep facilitates the use of prior information for creative problem solving. Subjects who had REM sleep displayed a significant improvement above NREM and quiet rest groups (P = 0.047, 1-way ANOVA and post hoc analysis). Strikingly, although the quiet rest and NREM nap groups received the same priming, they displayed no improvement on the primed RAT items, whereas the REM group improved by almost 40% above the morning performance.

Fig. 4.

Amount of sleep does not contribute to creative problem solving. TST and improvement on primed RAT items were not significantly correlated (r = 0.104, P = 0.53, trend line shown).

Fig. 5.

REM sleep does not improve creative problem solving without prior exposure. No group differences were found on the new RAT items (P = 0.261 1-way ANOVA), and PM performance was not different from baseline in the any of the three groups (CI 95%, −13.0 to 41.2%; CI 95%, −35.4 to 16.0%; and CI 95%, −51.0 to 15.4% for the REM, NREM, and rest groups, respectively). Although daytime sleep has been shown to improve a range of cognitive functions (perceptual, verbal, and motor learning; declarative and implicit memory) and to increase alertness and restore homeostatic drive, neither NREM nor REM sleep improves general creative problem solving in the absence of prior exposure (e.g., priming).

Fig. 6.

REM sleep improvements in creativity are dissociated from memory. Creative problem solving performance in the priming condition (y axis) and memory tasks (cued recall and recognition) are shown. The three groups perform equally well on all memory tasks, although REM sleep improvements in creativity are only seen in performance for primed unrelated items.