We've seen dream engineering in blockbuster movies like Christopher Nolan's Inception, and a new study shows that the science-fiction-style idea may be much closer to science fact than we realized.
A team led by researchers from Northwestern University has been able to prompt sleeping volunteers to dream about specific unsolved puzzles by using certain sounds.
What's more, the study participants (for whom the prompts worked) were much more likely to be able to find solutions to the same puzzles upon waking.
There are some caveats to be aware of with these techniques, but the research provides evidence that dreams can be manipulated to a certain extent, and that we can use them to find solutions that are useful when we emerge back into the real world.
"Many problems in the world today require creative solutions," says psychologist Ken Paller from Northwestern University.
"By learning more about how our brains are able to think creatively, think anew, and generate creative new ideas, we could be closer to solving the problems we want to solve, and sleep engineering could help."
In the experiement, the researchers recruited 20 participants, most of whom were lucid dreamers – that is, regularly able to realize they're dreaming during dream sequences. These volunteers were then set tough puzzles to complete, with a specific soundtrack accompanying each one.
When it came time for the slumber part of the study, the researchers tried to prompt dreams by playing back the soundtracks for half of the unsolved puzzles.
In some cases, the volunteers gave signals (like sniffs or eye movements) to indicate they had heard the cue and were dreaming about the puzzles.
The results were notable: The 12 participants whose dreams the researchers targeted with prompts reported that their dreams involved puzzles more often than not. Of those 12, their subsequent problem-solving ability the next day went up from 20 percent to 40 percent.
Across the whole group of participants, cued or uncued, the subsequent solving rate for puzzles that had appeared in dreams was 42 percent, as opposed to 17 percent for people who hadn't dreamed of the puzzles. It was as if some headway had been made towards the solution during the dream.
What's more, after getting the study participants to recount what happened in their dreams, the researchers found evidence that thoughts about the puzzles were breaking through – and that their minds were focusing on trying to solve them.
"Even without lucidity, one dreamer asked a dream character for help solving the puzzle we were cueing," says neuroscientist Karen Konkoly from Northwestern University.
"Another was cued with the trees puzzle and woke up dreaming of walking through a forest. Another dreamer was cued with a puzzle about jungles and woke up from a dream in which she was fishing in the jungle thinking about that puzzle."
These are significant findings, but as mentioned earlier, there are limitations to the study. To begin with, the number of participants was relatively low, and focused on lucid dreamers who are more aware during dream states, meaning other people might not experience the same phenomenon equally.
In addition, there might be other factors involved that trigger both dreaming about the unsolved puzzles, and being able to solve them at a better rate the next day. It's difficult to say with certainty that the dreams definitely contributed to the problem solving.
More certainty may come with future studies, and the researchers are eager to use the same approach to look at the impact of dreams on different types of creativity and different types of problems that need solving. It might also be useful to look more closely at why some people responded to dream prompts, and others didn't.
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"My hope is that these findings will help move us towards stronger conclusions about the functions of dreaming," says Konkoly.
"If scientists can definitively say that dreams are important for problem solving, creativity, and emotion regulation, hopefully people will start to take dreams seriously as a priority for mental health and wellbeing."
The research has been published in Neuroscience of Consciousness.