Researchers say two-way communication is possible with people who are asleep and dreaming.
Specifically, with people who are lucid dreaming — that is, dreaming while being aware you're dreaming.
In separate experiments, scientists in the U.S., France, Germany and the Netherlands asked people simple questions while they slept. Sleepers would respond by moving their eyes or twitching their faces in a certain way to indicate their answers.
"Since the '80s, we've known that lucid dreamers can communicate out of dreams by using these signals," says Karen Konkoly, a Ph.D. student at Northwestern University who is the first author on the study published this month in Current Biology.
"But we were wondering, can we also communicate in? Can we ask people questions that they could actually hear in their dreams that we could kind of have a more meaningful conversation?"
They were studying rapid-eye-movement sleep, which is the stage of sleep where people dream most vividly. In REM sleep, "every muscle in your body is completely paralyzed, except you can twitch and you can move your eyes," Konkoly tells Scott Simon on Weekend Edition. "So if you become lucid in a dream and you want to communicate, then when people are dreaming, they just look left-right, left-right, really dramatically. And then we know that they're communicating out."
Lucid dreaming is not common. So to study it, researchers recruited people who had experience with it and also trained people to try to make lucid dreaming more likely.
Before the participants went to sleep, they were also trained on how to communicate their answers. Special sensors measured people's eye movements or experts would judge their facial movements.
For example, a typical question would be to ask what is 8 minus 6. A 19-year-old American man was able to respond by moving his eyes left-right, left-right — two times — to signal "2." Researchers asked the question again, and he moved his eyes the same way two times again.
Out of the 158 trials among 36 participants, about 18% of the time, they were able to give correct answers. In another 18%, it wasn't clear whether participants were responding or not. They were wrong 3% of the time. Most often, 61%, participants didn't respond at all.
For the people dreaming, they didn't always interpret the questions they were hearing as a simple question from researchers. "Sometimes stimuli were perceived as coming from outside the dream, but other times, the stimuli emanated from elements of the dream, contextualized in a way that made sense in relation to ongoing dream content," the researchers write. One participant "heard the questions transposed over their dream as though it was God talking to them," Konkoly says.
The researchers write that their findings present "new opportunities for gaining real-time information about dreaming, and for modifying the course of a dream" and "could usher in a new era of investigations into sleep and into the enigmatic cognitive dimensions of sleep."
Konkoly says there's the possibility of one day doing a sort of "dream therapy" for talking down people experiencing lucid nightmares.
And if more reliable communication methods can be worked out, it could help people with creative activities and ideas. "People often use lucid dreaming or dreaming for a kind of artistic, creative inspiration," she says. "But in that dream state, your resources thus far are only the ones that you have in the dream."
So with the help of an awake person, Konkoly says it could be possible to "combine those logical advantages of wake with the creative advantages of dreams and maybe have some more applications."
Samantha Balaban and Ed McNulty produced and edited the audio interview.