Cutting-edge sleep science suggests we dream for at least six-and-a-half hours every night.
But experts remain divided on precisely why we dream.
Some think dreams are merely the result of random — and meaningless — firings of neurons, as the sleeping brain clears out debris from the day before and forms new memories.
Others, including those at the forefront of neuroscience, are convinced that dreams are the brain's ingenious way of joining the dots and suggesting solutions to problems while we sleep. By 'dramatising' our deepest anxieties and desires, they can show us what we really want and need in life.
Modern sleep research has even begun to reconsider the notion of 'precognitive dreams' — those that apparently show us an event before it's happened. Professor Robert Stickgold, of the Division of Sleep Medicine at Harvard Medical School in the U.S., co-author of a new book, When Brains Dream, says our sleeping brains are so good at mulling over waking concerns — and we all dream so much — the probability of a real-life event mirroring a dreamt-of one is far higher than we think.