Beware: If you must talk about your sleeping children being dullards or dumbos, make sure you keep plenty of distance between the conversation and their slumbering selves.

They might well hear you, and understand what’s being said … and end up with bad feelings. Or refuse to ever go to bed again.

How come?

US scientists have found that people in REM sleep, in the middle of a “vivid dream”, are able to understand what’s being said, can perceive questions and provide answers via eye movements and facial twitches.

Further, they can perceive and answer simple number problems.

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The sleepers were aware that they were dreaming, a common experience.

The researchers – led by Ken Paller, Professor of Psychology and
Director of the Cognitive Neuroscience Program at Northwestern University – are calling this style of communication “interactive dreaming”.

Say what?

“We found that individuals in REM sleep can interact with an experimenter and engage in real-time communication,” said Professor Paller, the lead author of the study. He was speaking in a prepared statement.

“We also showed that dreamers are capable of comprehending questions, engaging in working-memory operations, and producing answers.”

The professor allowed that most people might “predict that this would not be possible – that people would either wake up when asked a question or fail to answer, and certainly not comprehend a question without misconstruing it”.

IN (lower left) refers to methods by which information was transmitted from experimenter to dreamer. OUT (lower right) refers to methods whereby information was transmitted from dreamer to experimenter. Examples of three dreams (colour-coded for each input method) are illustrated below relevant excerpts from corresponding dream reports obtained following awakening. Graphic: Northwestern University

What prompted the experiment?

Professor Paller said that while dreams are a common experience, scientists still haven’t adequately explained them.

Relying on a person’s recounting of dreams is also fraught with distortions and forgotten details, he said.

This prompted the researchers to attempt communication with people during lucid dreams.

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“Our experimental goal is akin to finding a way to talk with an astronaut who is on another world, but in this case the world is entirely fabricated on the basis of memories stored in the brain,” the researchers write.

Their findings “could open the door in future investigations to learn more about dreams, memory, and how memory storage depends on sleep”.

How did they do this?

In four separate experiments, carried out at universities in the US, France, Germany and the Netherlands, 36 people were wired up for what’s known as polysomnography, also called a sleep study: The test recorded their brain waves, oxygen level in the blood, heart rate and breathing, as well as eye and leg movements.

The volunteers were stimulated with spoken words and beeping tones from a speaker, flashing lights and touch. The experiment worked better on some people than others.

One of the participants who “readily succeeded with two-way communication had narcolepsy and frequent lucid dreams.”

Among the others, some had “lots of experience in lucid dreaming” and others did not.

Overall, the researchers found that it was possible for people while dreaming to follow instructions, do simple arithmetic, answer yes or no questions, and tell the difference between different sensory stimuli.

Apart from the fun factor, what’s the useful point?

The researchers say that future studies of dreaming could use these same methods “to assess cognitive abilities” during dreams versus being awake.

They also could help verify “the accuracy of post-awakening dream reports”.

In a clinical setting, they suggest the experimental set-up could be used to help people solve problems during sleep or offer nightmare sufferers novel ways to cope.

And follow-up experiments are under way, in all four locations, with the aim “to learn more about connections between sleep and memory processing, and about how dreams may shed light on this memory processing”.