Everyone dreams – including machines, so it seems.
But why? There have been several theories put forward over the years from prophecies, to Freudian wish-fulfillment, to memory formation, to brain farts. But the very private and ethereal nature of dreaming makes it almost impossible to prove one way or the other.
However, research recently published in the journal Social Cognitive and Affective Neuroscience seems to support a long-held theory that suggests dreaming is a mechanism that helps us process our waking activities and emotions. This in itself isn't exactly breaking news, but this is the first time we have clear evidence to back it up.
To study the purpose of dreams, researchers at the Swansea University Sleep Lab came up with an innovative solution: They would compare the content and frequency of brainwaves while dreaming to the emotional intensity of waking life in the lead up to the dream.
Twenty students were recruited to take part in the study, two of whom had to be discounted for different reasons. Each one was what the researchers call frequent dream recallers, which means they are able to remember and describe their dreams five to seven times a week.
For 10 days, the volunteers were asked to complete a journal describing their waking life, detailing up to five major daily activities (which took up most of the day), five personally significant (i.e. emotional) events, and major concerns (essentially, anything that may have been preying on their mind that day, such as exam stress or financial worries). As well as disclosing what happened, they were asked to write down how it made them feel (say, excited) and rate the intensity of that emotion on a scale of one to three.
On day 10, the volunteers were connected to a non-invasive electroencephalography cap to record brainwave activity during slow-wave sleep (SWS) and rapid-eye-movement sleep (REM). After a 10-minute interval, the researchers would nudge the volunteers awake so that they could ask them to describe the content of their dreams. The cycle was repeated.
Eighteen volunteers reported at least one REM dream and 14 described at least one SWS dream. These were then compared to the content of the 10-day journal to see what, if any, connections there were between the two.
There were several interesting correlations, the researchers noted, between dreaming activity during the REM cycle and the information in the journals. First of all, the frequency of the theta brainwaves appeared to match the number of events mentioned – which basically meant that when there was more going on in a volunteer's waking life, the frequency of their theta brainwaves was higher.
Second, the content of their dreams appeared to match recent waking life experiences. For example, after speaking to her mom on the phone during the daytime, one volunteer reported seeing her mom in her dream.
And third, more emotionally intense activities were more likely to make an appearance in the dream than more mundane events.
"This is the first finding that theta waves are related to dreaming about recent waking life, and the strongest evidence yet that dreaming is related to the processing that the brain is doing of recent memories," Mark Blagrove, a psychologist at Swansea University, told New Scientist.
The researchers noticed no correlation between waking life and SWS dreaming, which could mean there is something else involved in dreaming during that cycle.
The next step is to see whether it's possible to manipulate REM sleep to improve memory and emotional processing.