We are typically unaware that we are asleep while we are in the throes of an emotional dream. But it is possible to be aware that we are dreaming, and it's even possible to gain control over our dreams.
Lucid dreaming occurs when you realize that you are dreaming. In some cases, the sleeping person can control what happens in the dream narrative. Some lucid dreams occur spontaneously, but people can also learn how to lucid dream. It is estimated that half of all people will have at least one lucid dream during their lifetime. But overall, lucid dreaming is rare, and even people who tend to lucid dream do so infrequently.
Lucid dreaming is mentioned throughout history, though the term wasn't coined until 1913 by Dutch psychiatrist Frederik van Eden. Paul Tholey, a German dream researcher who was involved in lucid dream research at Goethe University, developed a technique to induce lucid dreams in 1959. The reflection technique, as he called it, required people to ask themselves throughout the day if they were awake or dreaming. Budding lucid dreamers can also practice recognizing odd occurrences, or dream signs, that suggest they are in a dream and not reality.
Psychophysiologist Stephen LaBerge, scientist Denholm Aspy, and other dream researchers have studied lucid dreaming techniques extensively. They refer to a technique similar to Tholey's reflection method that they call "reality testing." This technique and one called the mnemonic induction of lucid dreams (MILD) have been among the most successful techniques for inducing lucid dreaming.
Reality testing involves questioning whether you are awake or dreaming throughout the day, then performing a test to determine which state you are in. Reliable reality tests could be rereading written text or closing your lips and inhaling. The hope is that if you make these actions habits while you are awake, then you can perform them reflexively when you are dreaming. These reality tests can cause strange occurrences in your dream, alerting you to the fact that you are dreaming.
The MILD technique involves similar reminders to the reality testing method but focuses those reminders at night rather than throughout the day and night. Before sleeping, the dreamer should repeat a mantra such as "next time I'm dreaming, I will remember that I'm dreaming." Then, you focus on reentering a recent dream and looking for clues that it is indeed a dream. You imagine what you would like to do within that dream.
For example, you may want to fly, so you imagine yourself flying within that dream. You repeat these last two steps (recognizing when you're dreaming and reentering a dream) until you go to sleep.
The MILD technique is often paired with the wake back to bed (WBTB) technique, where a person wakes up five or six hours after falling asleep and remains awake for a short time before falling back asleep. This could help increase mental alertness and target the REM sleep stage, when most lucid dreaming occurs.
Using these techniques, people have been able to have lucid dreams at will. Because this type of technique takes such mental training, however, some companies have introduced devices that attempt to induce lucidity through external stimuli.
While lucid dreaming may just seem like a cool way to enter fantasy land, it also has several applications outside of recreation. Lucid dreaming can help in personal development, enhancing self-confidence, overcoming nightmares, improving mental (and perhaps physical) health and facilitating creative problem-solving. For instance, lucid dreams could help reduce symptoms of anxiety or post-traumatic stress disorder.
Finally, lucid dreaming can function as a "world simulator." Just as a flight simulator allows people to learn to fly in a safe environment, lucid dreaming could allow people to learn to live in any imaginable world and to experience and better choose among various possible futures.
"How much you can practice your skills in the simulated world inside your own brain is, I think, a frontier of research," says Ribeiro.