The concept was popularized in Inception, where lucid dreamers could link up via technology and roam around the unconscious of a single dreamer.
But what's the basis for mutual dreaming in the real world?
In reality, mutual dreaming is very unlikely to exist - although we may, one day, develop technology to allow us to share "dreams".
This doesn't mean people can't share what seem like mutual dreams. The most commonly reported type is known as a meshing dream.
"Meshing" refers to different dreams which share certain elements.
For instance, you and your partner may both watch Lost together and then both of you dream about being stranded on an island.
Understandably, your shared waking experience leads to similar dreams. Even Freudian dream analysis offers an explanation for this kind of coincidence.
The other notion of shared dream is that of a meeting dream.
A meeting dream is the true meaning of mutual dreaming, where two or more people meet up and communicate inside the dream world.
But how would mutual dreaming be possible?
The definition implies one of at least two paranormal explanations: that we have the capacity for telepathy in dreams - or the dream world itself is an external construct, an alternate reality that could stem from an artificial simulation or other shared astral realm.
Dr Stephan LaBerge of The Lucidity Institute believes that mutual dreaming experiments in the lab can test the objective reality of shared dream worlds. That means that group dreaming can be used to prove whether the dream world is a genuine alternate reality or not.
Numerous group dreaming experiments and anecdotes have been published over the years.
To learn about some of these cases in detail, check out Group Dreaming: Dreams to the Tenth Power by Jean Campbell. In this book, Campbell traces the history of group dreaming experiments and how harnessing the power of mutual dreams would change our world today.
You can also take part in Dr Rory Mac Sweeneys ongoing Mutual Dream Experiment, in which dreamers are asked to select a "dream password" and attempt to exchange it with another dreamer on a specific night. Passwords are then matched online and dream content exchanged to further validate the match.
Let's look at some mutual dream experiments you can try in a non-lucid or lucid dream state.
Find a meshing dream partner willing to try this experiment. Choose an activity to do together during the waking day. Maybe go to a sports event, go hiking in the countryside, go to the zoo, or watch a movie.
Before you go to sleep that night, discuss your memorable experience with your meshing dream partner. Talk about elements that you found most interesting and set a clear intention to dream about your shared experience.
Ideally, you'll dream about your waking experience, or a closely related theme. If you become lucid, all the better. Seek out your meshing partner in the dream and have a lucid conversation with them. When you wake up, write down all the details of the dream, including the time you think it happened.
Compare notes with your partner and see how many dream symbols you can match. Don't influence each other's dream reports or change your recollection to fit their story. If you both report a dream conversation, pay particular attention to the details. This would be a nice example of a pre-arranged meshing dream.
There is nothing paranormal about this experiment, it is essentially a form of dream incubation. It's a pretty good demonstration of how our thoughts and experiences influence our dreams - even more so when these are compelling or novel experiences.
Find a meeting dream partner. If you have friends who lucid dream, invite them to try this experiment with you. Or you can seek out out others at our lucid dreaming forum. The goal is to have a lucid dream at the same time, on the same date, and both remember to enact the meet-up.
Select a location to meet up in. If you both live locally, you might choose a familiar place, like a park or town center. Otherwise choose a famous meeting spot, like Stone Henge or the Eiffel Tower. Make sure you know your destination in detail so you both have the same location to meet in mind.
If you do both visit the same location in your lucid dream, it could simply be a meshing dream - a coincidence - so you need to go one step further by having an unpredicted conversation. Share something you've never told them before, or make up a code-word on the spot.
By reporting the same unique conversation, you would generate anecdotal evidence for mutual dreaming that could warrant further investigation.
When you're exploring a paranormal phenomenon such as mutual dreaming, remember to record as much data as you can and to be objective.
This means trying to rationalize events as much as you can before jumping to conclusions. It's all too easy to trick ourselves into false beliefs, which may be much more exciting than writing off results as coincidence. But that does not lead us to greater truth.
One of the brilliant things about lucid dreaming is that it enables us to explore the dreaming mind in a way no other research method can. I urge all lucid dreamers to help science gain a greater understanding of the human mind, including the possible existence of mental phenomena like mutual dreaming.
If we're completely honest, lucid dreaming isn't really known for being the most social of interests. In fact, often it's a lone pursuit - just you, your dream journal and the landscape of your mind. But this technique called PAL (or Partner Assisted Lucidity) breaks down that wall and turns lucid dream exploration into a social event.
Members of our lucid dream forum have been asking how to create dream characters in lucid dreams. The most common problem is having characters who look nothing like they should. Or they seem disinterested in your company. Or they fail to show up on command altogether. So, how to combat this? It's a matter of finding creative solutions that bypass logical expectations.
To lucid dream, I recommend being able to remember at least one vivid dream per night. That will boost your self awareness in dreams (making lucidity more likely) and also means you can actually remember your lucid dreams. Which is nice. Here are four detailed tips on how to remember your dreams more frequently. And if you don't think you dream at all - trust me, you almost certainly do. It takes an extraordinarily rare sleep disorder to deprive someone of dream sleep.
It is estimated that these wise and wily Indians have been using mugwort in their healing and ritual practices for 13,000 years, where it is known as the ‘dream sage’. They use the herb to promote good dreams, which they consider an essential aspect of normal human functioning! But that’s not all...
Silene Capensis has been used for millennia by the Xhosa shaman of the river valleys in the eastern cape of South Africa, where it is known as Undela Ziimhlophe or 'white paths'. It's fragrant white flowers open only at night, when they emit a fragrant and almost hypnotising aroma. Also known as African Dream Herb or Ubulawu, Silene Capensis induces spectacularly vivid dreams - yet has never entered the mainstream and remains a fringe taste within western culture.
Experts agree that everyone is capable of having lucid dreams. Dreaming itself is a normal function of the mind. We all dream every night, even if we don't remember. And we all achieve conscious awareness while awake every single day. So what does it mean to combine these states? Why, the amazing ability to have conscious - or lucid - dreams. Sounds simple, doesn't it? So why do I keep hearing from people who say they can't achieve their first lucid dream?