Sleep and dreaming: Where do our minds go at night?
MARY SHELLEY’S involved a pale student kneeling beside a corpse that was jerking back to life. Paul McCartney’s contained the melody of Yesterday, while James Cameron’s feverish visions inspired the Terminator films. My dreams often feature a shrinking rabbit, which then turns into an insect that leaps across the lawn and under the neighbour’s fence.
With their eerie mixture of the familiar and the bizarre, it is easy to look for meaning in these nightly wanderings. Why do our brains take these journeys and why do they contain such outlandish twists and turns? Unfortunately for armchair psychoanalysts, Sigmund Freud’s attempts to interpret our dreams remain hotly disputed. Nevertheless, neuroscientists and psychologists have recently made big strides in understanding the way the brain builds our dreams, and the factors that shape their curious stories. Along the way, they have found startling hints that our use of technology may be permanently changing the very nature of this fundamental human experience.
Anyone who has ever awoken feeling amazed by their night’s dream only to forget its contents by the time they reach the shower will understand the difficulties of studying such an ephemeral state of mind. Some of the best attempts to catalogue dream features either asked participants to jot them down as soon as they woke up every morning or, better still, invited volunteers to sleep in a lab, where they were awoken and immediately questioned at intervals in the night. Such experiments have shown that our dreams tend to be silent movies - with just half containing traces of sounds. It is even more unusual to enjoy a meal or feel damp grass beneath your feet - taste, smell and touch appearing only very rarely.
Similar studies have tried to pin down some of the factors that might influence what we dream about, though they have struggled to find anything reliable. You might expect your dreams to reveal something about your personality, but traits such as extroversion or creativity do not seem to predict features of someone’s journeys through the land of nod. Shelley and McCartney’s dreams aren’t that unlike ours.
“People’s dreams seem to be more similar than different,” says Mark Blagroveat Swansea University in the UK. That suggests common symbols in dreams might represent shared anxieties and desires, but attempts to find these have also been disappointing - something like a surreal shrinking rabbit, for instance, probably reveals nothing “that you didn’t already know”, says Blagrove, gnomically.
A more fruitful approach has been to look at the brain’s activity during sleep for clues to the making of our dreams. Of particular interest is the idea that sleep helps to cement our memories for future recall (see “What is the point of sleep?”). After first recording an event in the hippocampus - which can be thought of as the human memory’s printing press - the brain then transfers its contents to the cortex, where it files the recollection for long-term storage.
This has led some psychologists, including Blagrove, to suspect that certain elements of the memory may surface in our dreams as the different pieces of information are passed across the brain. Studying participants’ diaries of real-life events and comparing them with their dream records, his team has found that memories enter our dreams in two separate stages. They first float into our consciousness on the night after the event itself, which might reflect the initial recording of the memory, and then they reappear between five and seven days later, which may be a sign of consolidation.
Even so, it is quite rare for a single event to appear in a dream in its entirety - instead, our memories emerge piecemeal. “What usually happens is that small fragments are recombined into the ongoing story of the dream,” says Patrick McNamara at Northcentral University in Prescott Valley, Arizona. And the order in which the different elements appear might reflect the way a memory is broken down and then repackaged during consolidation.
One of McNamara’s studies, which compared one individual’s dream and real-life diaries over a two-month period, found that a sense of place - a recognisable room, for instance - was the first fragment of a memory to burst onto the subject’s dreamscape, followed by characters, actions and finally physical objects.
While it may cement a memory into our synapses during consolidation, the sleeping brain also forges links to other parts of your mental autobiography, allowing you to see associations between different events. This might dredge up old memories and plant them in our dreams, which in turn might explain why we often dream of people and places that we haven’t seen or visited for months or even years. It could also lie behind those bizarre cases of mistaken identity while dreaming, when objects or people can appear to be one thing, but assume another shape or character - such as the shape-shifting rabbit that haunts my dreams. “It’s a by-product of the way the brain blends different elements,” says McNamara.
33% of dreams contain bizarre elements impossible in everyday life
Our dreams are more than a collection of characters and objects, of course. Like films or novels, they tell their stories in many different styles - from a trivial and disordered sequence to an intense poetic vision. Our emotional undercurrents seem to be the guiding force here. Ernest Hartmann, a psychiatrist at Tufts University in Medford, Massachusetts, has studied the dream diaries of people who have recently suffered a painful personal experience or grief. He found that they are more likely to have particularly vivid dreams that focus on a single central image, rather than a meandering narrative. These dreams are also more memorable than those from other, more placid times.
Why would our emotions drive the form of our dreams in this way? Hartmann suspects this might also reflect underlying memory processes - our emotions, after all, are known to guide which memories we store and later recall. Perhaps the intense images are an indication of what a difficult process it is integrating a traumatic event with the rest of our autobiography. The result may help us to come to terms with that event. “I think it makes a new trauma less traumatic,” says Hartmann, though he readily admits that his hypothesis is difficult to prove.
Despite these advances, many, many mysteries remain. Top of the list is the question of the purpose of our dreams: are they essential for preservation of our memories, for instance - or could we manage to store our life’s events without them? “There’s no consensus,” says McNamara. But understand their origins, he says, and we would get a better grasp on consciousness in general.
Then there’s the impact of our lifestyles on our night-time consciousness, with some research suggesting that TV may have caused a major shift in the form and content of our dreams (see “Monochrome or technicolour?”). If a few hours of television a day can change the nature of our dreams, just imagine what our intense relationships with computers are doing. Eva Murzyn at the University of Derby, UK, for instance, has found that people who take part in the World of Warcraft online role-playing game incorporate its user-interface into their midnight adventures.
And, inspired to look into it by her own son’s gaming, Jayne Gackenbach at Grant MacEwan University in Edmonton, Canada, has found that players are beginning to report a greater sense of control over their dreams, with the feeling that they are active participants inside a virtual reality. She points out that gamers are more likely to try to fight back when they dream of being pursued by an enemy, for instance. Ironically, this interaction seems to make their dreams less scary and more exciting. “They say things like - ‘this was a nightmare, but it was awesome’. They are invigorated by it,” Gackenbach says.
If you’re after a more peaceful night, you might want to take inspiration from Hervey de Saint-Denys, an early dream researcher in the 19th century who found that certain scents could direct his dreams. To prevent his own expectations from clouding the results, he asked his servant to sprinkle a few drops of perfume on his pillow on random nights as he slept. Sure enough, he found that it led his dreams to events associated with that particular scent. More generally, recent studies confirm that sweet smells can spark emotionally positive dreams.
Then again, if you are like me you may prefer to let your subconscious direct your nightly wanderings. As unsettling and upsetting as they can sometimes be, it is their mystery that makes dreams so enchanting.
7 to 9 hours of nightly shuteye is best for adults
Monochrome or technicolour?
Strong hints that technology drives our dreams emerged with puzzling reports in the 1950s that most people dream in black and white. Why? Curiously, this seemed to change over the following decade, and by the late 1960s the majority of people in the west seemed to dream in colour again. What could cause the transformation? Eva Murzyn at the University of Derby, UK, puts it down to changes in broadcasting - TV burst into colour at about the same time as a generation’s dreams emerged from greyscale. Intriguingly, she has found that a difference still lingers to this day - those born before the advent of colour TV are still more likely to report dreaming in black and white than those born afterwards (Consciousness and Cognition, vol 17, p 1228).