DREAMS ARE clearly important. All humans have them, as do animals from cats to elephants. Neuroscientists believe they are involved in the processing of memories. Yet studying them is limited by the fact that dreamers themselves cannot talk to anyone while they are asleep. Researchers must rely on the unreliable recollections of people who have woken up. Now, though, a team of scientists led by Ken Paller, a neuroscientist at Northwestern University, think they may have found a way around that problem.
Dr Paller’s starting point was the fact that lucid dreams—in which sleepers are aware they are dreaming—seem to be associated with only one kind of sleep, known as “rapid eye movement” (REM) sleep. During REM sleep, brain activity looks similar to that seen during waking hours. Past research has shown that it is possible for people to be influenced by events taking place in the outside world during REM sleep. So Dr Paller speculated that it might be possible to reach out to people in such states, and to get answers back.
As described in Current Biology, Dr Paller, along with colleagues in France, Germany and the Netherlands, gathered 35 volunteers. All were trained to be mindful of their mental state, and to analyse whether they thought they were awake or in a dream. In some labs (though not all) that training was accompanied by a distinctive sound. That same sound was repeated, as a cue, while the participants were in REM sleep. Participants were also trained to make distinct left/right eye movements to indicate they were aware they were dreaming, and in response to questions. They practised interpreting numbers conveyed as flashes of light, taps on their arm, or even as spoken words.
Thus prepared, the volunteers were wired up with electrodes and sent back to the land of Nod. Sometimes the researchers would initiate contact with their dreamers by playing the sound cue and waiting for an eye signal in response. At other times, the participants themselves sent an eye signal of their own accord. Once it was clear that contact had been made, the researchers asked their questions, and waited for answers.
Interviewed upon waking, the participants reported that the questions had been incorporated into their dreams. One said an audio question was heard through a car radio; another that flashes of light sent by the researchers manifested as a flickering light. One of the numerical questions even manifested as the street number of a house. Intriguingly, participants occasionally “remembered” a mathematics problem different from the one they had been asked—despite having given the correct answer, via eye movements, at the time.
The method often did not work. Participants signalled that they were engaged in lucid dreaming in just 26% of the sessions. Of that group, 47% answered at least one question put to them correctly. But it proves a point. Dr Paller and his colleagues say their findings refute the notion that attempting communication with dreamers is pointless. And that, in turn, may help researchers shed some light on what dreams are for, and how they work. ■
This article appeared in the Science & technology section of the print edition under the headline “The interpretation of dreams”