In the movie Inception, Leonardo DiCaprio enters into other people’s dreams to interact with them and steal secrets from their subconscious. Now, it seems this science fiction plot is one baby step closer to reality. For the first time, researchers have had “conversations” involving novel questions and math problems with lucid dreamers—people who are aware that they are dreaming. The findings, from four labs and 36 participants, suggest people can receive and process complex external information while sleeping.
“This work challenges the foundational definitions of sleep,” says cognitive neuroscientist Benjamin Baird of the University of Wisconsin, Madison, who studies sleep and dreams but was not part of the study. Traditionally, he says, sleep has been defined as a state in which the brain is disconnected and unaware of the outside world.
Lucid dreaming got one of its first mentions in the writings of Greek philosopher Aristotle in the fourth century B.C.E., and scientists have observed it since the 1970s in experiments about the rapid eye movement (REM) phase of sleep, when most dreaming occurs. One in every two people has had at least one lucid dream, about 10% of people experience them once a month or more. Although rare, this ability to recognize you are in a dream—and even control some aspects of it—can be enhanced with training. A few studies have tried to communicate with lucid dreamers using stimuli such as lights, shocks, and sounds to “enter” people’s dreams. But these recorded only minimal responses from the sleepers and did not involve complex transmission of information.
Four independent teams in France, Germany, the Netherlands, and the United States tried to go further and establish complex two-way communication during dreams, using speech and asking questions the sleepers had never heard in their training. They recruited 36 volunteers, including some experienced lucid dreamers and others who had never experienced a lucid dream before but remembered at least one dream a week.
The researchers first trained participants to recognize when they were dreaming, by explaining how lucid dreaming works and demonstrating cues—sounds, lights, or finger tapping—that they would present while dreamers slept. The idea was those cues would signal to participants that they were dreaming.
Nap sessions were schedueled at different times: some at night, when people would regularly go to bed, and others early in the morning. Each lab used a different way to communicate with the sleeper, from spoken questions to flashing lights. Sleepers were told to signal they had entered a lucid dream and answer questions by moving their eyes and face in particular ways—by, for example, moving their eyes three times to the left.
As the participants fell asleep, the scientists monitored their brain activity, eye movement, and facial muscle contractions—common indicators of REM sleep—with electroencephalogram helmets outfitted with electrodes. Out of a total of 57 sleeping sessions, six individuals signaled they were lucid dreaming in 15 of them. In those tests, researchers asked the dreamers simple yes or no questions or math problems, like eight minus six. To answer, dreamers used the signals they had been taught before falling asleep, which included smiling or frowning, moving their eyes multiple times to indicate a sum, or, in the German lab, moving their eyes in patterns that matched Morse code.
The researchers asked 158 questions of the lucid dreamers, who responded correctly 18.6% of the time, the researchers report today in Current Biology. The dreamers gave the wrong answer to only 3.2% of the questions; 17.7% of their answers were not clear and 60.8% of the questions got no response. The researchers say these numbers show the communication, even if difficult, is possible. “It is proof of concept,” Baird says. “And the fact that different labs used all these different ways to prove it is possible to have this kind of two-way communication … makes it stronger.”
After several questions, the dreamers were woken up and asked to describe their dreams. Some remembered the questions as part of a dream: One dreamer reported math problems coming out of a car radio. Another was at a party when he heard the researcher interrupting his dream, like a narrator in a movie, to ask him whether he spoke Spanish.
The experiment provides a better way to study dreams, says lead author Karen Konkoly, a cognitive neuroscientist at Northwestern University. “Almost everything that’s known about dreams has relied on retrospective reports given when the person is awake and these can be distorted.” Konkoly hopes this technique could be used in the future therapeutically to influence people’s dreams so they can better deal with trauma, anxiety, and depression.
Sleeping “conversations” might also help the dreamer solve problems, learn new skills, or even come up with creative ideas, Baird says. “The dream is a highly associative state that may have advantages when it comes to creativity.”
University of Rochester cognitive neuroscientist Michelle Carr, who was not involved in the study, says she is excited about such future applications. But she stresses that retrospective dream reports can’t be replaced. “When you are in a dream, your reporting abilities are quite limited,” she says.
Changing people’s thoughts during dreams is still science fiction, stresses co-author and cognitive neuroscientist Ken Paller, also at Northwestern. Nevertheless, he thinks the experiment is an important first step in communicating with dreamers; he likens it to the first conversation using a telephone or talking to an astronaut on another planet. Dreamers live in a “world entirely fabricated of memories stored in the brain,” he says. Now, researchers appear to have found a way to communicate with people in that world.