Lucid dreaming, or the ability to become aware that you're dreaming while you are actively doing so, is a rare psychological state that has long fascinated scientists. So far, scientists had been able to show how participants can process external cues while remaining asleep but never communicate back while asleep.

This has changed with the publication of a new research study in Current Biology detailing how scientists were able communicate in real-time with lucid dreamers instead of having to wait for study participants to wake up and talk about their dreams. 

While sleeping, the volunteers communicated with the researchers, responded to questions, and answered math problems by moving their eyes left and right and contracting their facial muscles. For example, one study participant was asked to solve the math problem "four minus zero" and answered by moving their eyes left and right four times each — all while sleeping. Moreover, volunteers typically were able to recollect what happened upon awakening.

The possibility to hear the outside world during the stage of dreaming opens up a world of opportunities for some people including, but not limited to, interactive dreaming, recreational enjoyment or even lucid dreaming therapy.