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IT WAS 332 BC. Alexander the Great was besieging the Phoenecian city of Tyre, the naval base of his great Persian enemy. One night, he dreamed that a satyr was mocking him from a distance. His dream interpreter broke down the word ‘satyr’ into ‘as’ and ‘tyros’, meaning ‘Tyre is yours’. Alexander then attacked the city, and conquered it.
This story, told by Greek historian Plutarch, is “the most beautiful example of a dream interpretation that has been handed down to us from antiquity,” wrote Sigmund Freud in his classic book, The Interpretation of Dreams.
There have been many stories like this: throughout history, dreams have often been seen as messages, either clear or in code – as warnings from the gods, or prophecies, or, if you believe Freud, clues to our repressed sexual desires.
In Ancient Egypt, priests were also dream interpreters, while in the Bible, divine revelations often came in dreams. More recently, images in dreams have been credited with inspiring everything from the Periodic Table of Elements and the structure of benzene, to Mary Shelley’s Frankenstein and even the sewing machine.
Modern neuroscience, though, has been more interested in why dreams occur and what they might do for us – or, more specifically, for the brain. And while there’s still a lot of debate, it’s starting to look as if dreaming may be important for memory and our emotional well-being.
What’s surprising is that there has also been a recent revival in the study of dream content; and that it’s providing fascinating new insights into what we dream about, and why.
In fact, dreams do have meaning, argues Patrick McNamara, an expert on sleep and dreams at Boston University, Massachusetts.
As you sleep, you cycle through five stages. Two stages of light sleep, then two of deep sleep are followed by REM (Rapid Eye Movement) sleep, which is characterised by rapid breathing (and eye movements, of course) plus a rising heart rate. Most people equate dreams with REM.
But dreams and nightmares also occur in stage four, when you’re in a deep ‘slow-wave’ sleep. McNamara has found that the kind of dreams people have in REM sleep are different from stage four sleep. “REM dreams are more story-like, with more emotion, more aggression and more unknown characters,” he says.
And it seems that these two dream stages might have different functions, not least when it comes to memory.
In 2009, a team at the Edmond and Lily Safra International Institute of Neuroscience of Natal, Brazil, reported a memory study involving the shoot-’em-up video game Doom. Eleven expert players and 11 casual players spent two nights in the lab. On the first night, they were woken during REM sleep and asked to recall their dreams.
The next night, they played Doom for an hour before bed, then had their dreams catalogued in the morning, before playing the game again.
