In the new sci-fi thriller "Inception," Dom Cobb, played by Leonardo DiCaprio, is a dream snatcher. He's an industrial spy who steals secrets by means of "extraction" when his victims are at their most defenseless: when they are asleep and dreaming. But he has an even rarer ability, that of "inception": He can plant an idea in someone's sleeping mind, and watch the dreamer act on it when he awakens. "The most resilient parasite is an idea," he says.
"Inception" lies somewhere between a James Bond film and "The Matrix." But it does contain some science. Here's a spoiler-free guide to the movie's take on dreams and the unconscious mind.
Is it possible to directly access someone's dreaming mind?
In the movie, the dream snatchers use a drug called somnacin and a dream machine to upload a scenario into someone's sleeping mind. One or more of the dream snatchers hook themselves up to the machine, go to sleep themselves and enter the target's dream. This fictional dream machine is called a Portable Automated Somnacin IntraVenous (PASIV) Device.
A device already exists that can effectively read someone's mind. A functional MRI scanner takes snapshots of brain activity, and then software re-creates images of what the subject was looking at. Researchers say it has the potential one day to record someone's dream -- without the mess and danger (or the fun) of actually sharing that dream.
Using a drug like somnacin to access a sleeping mind is not possible, but there are drugs that can drastically modulate our sleep. These include modafinil, which can promote continuous wakefulness, and new classes of sleeping pills that can deliver "super sleep," in which, for instance, four hours of sleep can equate to six.
How can I control my dreams?
The easiest way to experience a lucid dream -- in which the sleeper is aware he or she is dreaming and can actively participate in the dream -- is to train yourself to ask, "Am I dreaming?" while you are asleep. Keen video gamers, probably because they focus on a single task for hours per day, are particularly good at lucid dreaming.
The dream team of "Inception" is highly trained at this, which may be why they are able to perform complex tasks while asleep, such as reading, which most normal lucid dreamers find difficult. Some of the characters in the movie have also militarized their dreamscapes, adding protectors, to guard themselves against invasive dream snatchers.
Do dreams have to obey the laws of physics?
This is a fondly debated topic, and "Inception" has it both ways. Sometimes impossible things happen -- in one dream Paris gets folded like a huge sheet of paper -- and optical illusions become "real." The endless staircases created by M.C. Escher, for example, exist in "Inception" dreams thanks to a manipulation something like those that occur in 3-D virtual environments.
However, the "Inception" dreams follow some real-life rules. As writer and producer Jeff Warren wrote about his own dream investigations: "Without sensory input, consciousness appears to behave in predictable ways. Informal laws can be deduced, for example, the 'law of self-fulfilling expectations' (what you expect to happen will happen), the 'law of narrative momentum' (linger too long in one place and the dream world begins to fray)."
In "Inception," the dream world "frays" when external influences from the real world intrude.
What is the function of dreams?
Freud thought that dreams expressed our repressed desires. And so they do, sometimes, but much modern research suggests that dreams help in information processing and memory storage.
Dreams occur in both rapid-eye movement (REM) sleep and non-REM sleep. REM dreams are more storylike, with emotion and aggression; non-REM dreams often involve friendly social interactions. People with depression often experience more REM sleep than non-depressed people.
How does subjective time pass in a dream?
In "Inception," dream time runs much more slowly than real time, and there is a scaling effect, such that if you dream within a dream, time passes even more slowly. So five minutes of real time equals one hour of dream time, a five-minute dream inside a dream equals one week of real time, and so on.
This is perhaps the cleverest part of the movie, but though intuitively pleasing, there is little evidence for it. In fact, there is some evidence that in lucid dreams, at least, the perception of time is similar to what it is when the dreamer is awake.
A more pressing question for researchers is what happens when our brain's time perception goes faulty. In fact, the illusion of time passing may be created by the brain itself, which is at least as much of a head-scratcher as the plot of "Inception."
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