After being challenged by a video game problem, sleep increases the chance to solve it

Abstract

In the past years many studies have demonstrated the role of sleep on memory consolidation. It is known that sleeping after learning a declarative or non-declarative task, is better than remaining awake. Furthermore, there are reports of a possible role for dreams in consolidation of declarative memories. Other studies have reported the effect of naps on memory consolidation. With similar protocols, another set of studies indicated that sleep has a role in creativity and problem-solving. Here we hypothesised that sleep can increase the likelihood of solving problems. After struggling to solve a video game problem, subjects who took a nap (n = 14) were almost twice as likely to solve it when compared to the wake control group (n = 15). It is interesting to note that, in the nap group 9 out 14 subjects engaged in slow-wave sleep (SWS) and all solved the problem. Surprisingly, we did not find a significant involvement of Rapid Eye Movement (REM) sleep in this task. Slow-wave sleep is believed to be crucial for the transfer of memory-related information to the neocortex and implement intentions. Sleep can benefit problem-solving through the generalisation of newly encoded information and abstraction of the gist. In conclusion, our results indicate that sleep, even a nap, can potentiate the solution of problems that involve logical reasoning. Thus, sleep's function seems to go beyond memory consolidation to include managing of everyday-life events.

Figure 1. Study protocol.

One week before the experimental day, subjects filled out questionnaires and the actigraphy begins. On the experimental day, practice session (PS) started at 1:00pm, after having a snack, subjects had an incubation interval of 90 minutes, starting around 1:30pm, which could be filled with sleep (Sleep group) or quiet wakefulness (Control group). The testing session (TS) was performed after the incubation interval, between 3:00pm to 4:00pm. At the beginning of each session subjects were required to fill out the Karolinska Sleepiness Scale (KSS).

Figure 2. Speedy Eggbert Mania®.

A) Representative schema of the levels of the game. The game is structured in four different scenarios (A to D) each one with four levels (1 to 4). Subjects started playing the first level (A1 to D1), then moved to the second level (A2 to D2) and so on. B) Example of one level (C3) of the game. Reprinted from Epsitec under a CC BY license, with permission from Epsitec, original copyright 2000.

Figure 3. Effect of sleep on problem-solving.

Bars show the percentage of subjects in each group. Blue represents the percentage of subjects who solved the problem; yellow represents the percentage of subjects who did not. Sleep group n = 14 (solvers n = 12, non-solvers n = 2). Control group n = 15 (solvers n = 7, non-solvers n = 8).