Scientists have successfully "talked" to a sleeping person in real-time by invading their dreams, a new study shows. The researchers say it's like trying to communicate with an astronaut on another world.
Dreamers can follow instructions, solve simple math problems and answer yes-no questions without ever waking up, according to the results of four experiments described Thursday (Feb. 18) in the journal Current Biology.
The researchers communicated directly with sleeping participants by asking them questions and having them respond with eye or facial movements during lucid dreams — when people are at minimum aware that they are dreaming. (Some lucid dreamers can control what happens in their dreams.)
"You might expect that if you were to try to communicate with somebody who was asleep, they just wouldn't answer," study first author Karen Konkoly, a cognitive neuroscientist at Northwestern University in Illinois, told Live Science. Although Konkoly hoped the real-time communication would work, she said she "didn't believe it" when someone first responded to her questions from their dream.
Related: 7 mind-bending facts about dreams
People dream every night, but scientists don't fully understand why we dream. Studying dreams is difficult because people often forget or distort details after waking up. That's in part because the brain doesn't form many new memories while sleeping and has a limited capacity to accurately store information after the dream has ended, according to the study.
To overcome this limitation, the researchers attempted to communicate with people while they were still dreaming. Because the study participants were having lucid dreams, that meant they could make a conscious effort to respond to cues coming in from the outside world, the researchers hypothesized.
Researchers placed electrodes on the participants' heads, to measure their brainwaves; next to their eyes, to track eye movements; and on their chin, to measure muscle activity. They used this data to determine when the participants entered the rapid eye movement (REM) stage of sleep, when lucid dreams are most likely to occur, Konkoly explained.
Four independent lab groups in the U.S., Germany, France and the Netherlands conducted four separate experiments. The researchers used several techniques across the experiments to communicate with dreamers during REM sleep, including asking them spoken questions and giving them encoded messages in flashing lights, beeping tones and physical taps, that the dreamers had been trained to decipher. If dreamers received and understood the question or message during a lucid dream, they then responded with a set of distinctive eye or facial movements that were interpreted by the electrodes.
"Such two-way communication — from outside to inside the dream and back out again — is something that may seem to belong to the domain of science fiction," Pilleriin Sikka, senior lecturer in cognitive neuroscience at Sweden's University of Skövde and postdoctoral researcher at Finland's University of Turku, told Live Science in an email. "Given how challenging it is to induce lucid dreams in the laboratory and that the study was carried out by four independent laboratory groups, the researchers' effort is remarkable," she said.
Sikka however notes that it was very difficult for the experiments to achieve this communication successfully — it was attained in just six of 36 participants across many attempts — which raises questions about the extent to which the findings can be generalized and replicated.
About 23% of people have a lucid dream once a month or more, according to a 2016 research paper published in the journal Consciousness and Cognition. Konkoly helped induce lucid dreams in her experiments by training participants to associate a sound with a lucid state of mind and then presenting them with that sound, or cue, again during sleep. (Those who want to try to experience lucid dreams for themselves can download an app called Lucid, developed by students in the Northwestern University lab, Konkoly said.)
The researchers suggest that the method in the experiments could be adapted to potentially help tailor a person's dream to a specific need, such as learning or coping with emotional trauma, according to the study.
Robert Stickgold, a professor of psychiatry at Harvard Medical School and director of the Center for Sleep and Cognition at Beth Israel Deaconess Medical Center, said the results of the study were "groundbreaking", in an email to Live Science.
"The retrospective nature of dream reports represents a challenge to the study of dreams. Two-way, real-time communication between researchers and lucid dreamers immersed in REM sleep offers a new and exciting window into the study of dreams and dreaming," Stickgold said. Still, it isn't clear "how easily these initial findings can be extended to real-life applications or to answer more complex questions regarding the nature and function of dreams".
Some footage from the lucid dreaming experiments was captured for an online NOVA, PBS documentary called "Dream Hackers: Bridge to Your Hidden Brain", which is available to watch on YouTube from Feb. 18.
Originally published on Live Science.