A slew of apps promise to encourage "lucid dreaming". So why is there such enthusiasm around the idea of controlling dreams, asks Sam Judah.
"You're only bound by gravity if you believe in it," says Rory Mac Sweeney, impatiently.
He is explaining the logic of a dream world which he not only visits each night, but apparently has active control over, flying at will through lush forests or launching himself upward into the night sky.
It sounds implausible, but the phenomenon is known as lucid dreaming.
Lucid dreaming technically refers to any occasion when the sleeper is aware they are dreaming. But it is also used to describe the idea of being able to control those dreams.
Once confined to a handful of niche groups, interest in lucid dreaming has grown in recent years, spurred on by a spate of innovations from smartphone apps to specialist eye masks, all promising the ability to influence our dreams.
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Paul McCartney (left) and John Lennon
Samuel Taylor Coleridge, the Romantic poet, is said to have composed his masterpiece Kubla Khan after an opium-influenced dream. The writing of the poem was famously interrupted by a knock on the door.
Former Beatle Sir Paul McCartney says that he dreamed the melody for his well-known song Yesterday, which appears on 1965 album Help!
President Abraham Lincoln is said to have dreamed his assassination and described it to his wife just a few days before the event.
The great Indian mathematician Srinivasa Ramanujan said that his work was inspired and influenced by the Hindu goddess Namagiri, who visited him in dreams.
Chinese philosopher Zhuangzhi famously dreamed he was a butterfly, leading him to an examination of the philosophy of mind, language and epistemology.
"A couple of years ago there were about four or five people organising meetings" says Mac Sweeney, a dentist and lucid dreaming expert from Islington, London. "Now there are closer to 50, and that's in the capital alone."
It's not just lucid dreaming groups that are booming. Attendance at more traditional dream interpretation groups like the Academy of Dreams, in Euston, are up, and elsewhere people are paying up to £40 an hour for private interpretation sessions.
Michael Cave, who works at a bank in Marylebone, London, is one of the newcomers. As with many recent recruits, he was attracted by adverts for lucid dreaming meetings on social networking sites, one of the factors behind the trend.
"I'm quite a sceptical person and would only believe it if I experienced it for myself. Now, though, I've achieved lucidity a number of times."
In addition to the group meetings, Michael has toyed with Dream:ON, the most popular of the many new smartphone apps now available.
Created by psychologist Richard Wiseman, the app has seen over half a million downloads in just six weeks.
"The new wave of interest is led by technology," says Wiseman, whose app claims to allow users to choose their dream before bed, and plays sound cues once they have entered the right phase of sleep.
"When I selected birdsong, for example, I found myself dreaming that I was in a green and sunny field," says Cave.
Whilst this isn't strictly lucid dreaming, as it doesn't offer users control from within a dream, there are many more which promise just that.
Singularity Experience, Dreamz, Sigmund and Lucid Dream Brainwave all work in a similar way, by playing subtle audio cues whilst the user is asleep. Not enough to wake them, but hopefully sufficient to trigger awareness inside a dream.
Man using smartphone These things normally keep you awake...
More curious still are the specialist sleep masks which attempt to make a lucid experience more likely.
The Remee, from Brooklyn based inventors Duncan Frazier and Steve McGuigan, is the latest such device, and it confirmed the public appetite for dream control.
Attempting to raise $35,000 to develop the product, the pair saw a deluge of public contributions totalling over $500,000.
"We wanted to bring lucid dreaming into the mainstream," says McGuigan.
By firing a set of LED lights over the eyelids once the user is asleep, the mask claims to offer a visual reminder to a dreamer who hopes to gain control.
The tool isn't the first of its kind, however. An early "dream machine" was created in the late 70s by Keith Hearne.
A lucid dreamer himself, Hearne was determined to prove the phenomenon in a series of trials at Liverpool University.
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From a bed in a laboratory, wired up to a polygraph machine, a sleeping subject was able to move his eyes according to a pre-agreed pattern - left then right many times in quick succession.
The study was repeated by Steve LaBerge in California. Allan Hobson, a neuroscientist at Harvard Medical School, confirms this view. "For the first time you could show that there were objective correlates between dreams and the outside world."
But references to lucid dreaming stretch back at least as far as Tibetan Buddhists in the 8th century, for whom it was just one stage in the practice of "dream yoga".
In 1867 Marquis d'Hervey de Saint-Denys even wrote an instruction manual entitled Dreams and How To Guide Them before a Dutch psychiatrist, Frederick Van Eeden, finally coined the term "lucid dreaming" in the early 20th century.
More recently it has been hinted at by films like Inception and the Science of Sleep, which have no doubt contributed to its allure.
"Inception has been a major factor," says Mac Sweeney, "it's helped to shed the new age connotations. Now it's seen as glamorous, even sophisticated."
Does the flurry of new technology actually work though, and how likely are you to experience a lucid dream yourself?
Disappointingly, Hobson tells us, "lucid dreaming is very hard work and won't happen for everyone".
There's no guarantee that the apps will help, either. Success rates in those we asked were low, even among experienced lucid dreamers.
Ultimately, the lucid dreaming adherents say attaining the revered state requires discipline and practice, and the key is being able to quickly distinguish dreams from reality.
One step they advocate is to regularly perform a simple reality test. Hold your nose, close your mouth, and try to breathe. If you're able to inhale, it's a signal that you're inside a dream, which you can begin to manipulate.
Woman asleep with eye mask This could help you sleep
For those who do achieve lucidity the rewards can be great, not just in the dreams but in their waking lives too.
Caroline McCready, an artist and regular at lucid dreaming meetings, says: "You're able to ask yourself very profound questions, and get answers. I've come to understand a lot of my fears now because I'm able to confront them directly in dreams."
The process "challenges everything", Mac Sweeney suggests. "You start to lose a lot of conceited notions about yourself and your relationships with other people."
For Hobson, the neuroscientist, the benefits of being able to achieve lucid dreaming are much simpler.
"We don't really know if there are real psychological advantages, but I can tell you that it has huge entertainment value. It's like going to the movies and not paying for your ticket."