If you wake up in the morning with no recollection of your dreams, did you actually have any? New research has found that we're all dreamers, even if we believe we aren't - typically around 6.5 percent of people surveyed say they never have any dreams.
Researchers in France decided to take these potentially fallible self-assessments out of the equation, and independently monitored volunteers while they were asleep. All of the volunteers had a sleep behaviour disorder called RBD (Rapid Eye Movement Behaviour Disorder), where REM sleep is accompanied by physical movement - by noting this movement, the researchers could assess whether someone was actually dreaming or not, even if they later had no recollection of it.
Of the 289 participants, 2.7 percent reported they hadn't dreamed for more than a decade and 1.1 percent said they'd never dreamed. However, movements observed during sleep suggested these people were dreaming after all, acting out their dreams in bed as those with RBD are liable to do. The study, which was published in the Journal of Sleep Research mentions a number of example case studies to emphasise the point.
"Patient 1 was a 73-year-old man," reads the report. "He used to recall dreams as a child, but stopped recalling dreams from the age of 20 years. At the age of 53 years, he started talking, yelling, and moving his legs and arms while asleep… [the recorded video shows] the patient arguing, swearing profanities, kicking, boxing and throwing items towards an invisible individual during REM sleep… with no subsequent dream recall despite the nurse's immediate inquiry."
The physical movements exhibited by this patient and others - often accompanied by speaking or shouting - would certainly suggest that some kind of dreaming is going on during the deepest parts of sleep, yet all memory of it had apparently vanished by the time the subjects woke up again.
There are a couple of limitations to the study to bear in mind: first, all of the participants in the study were already receiving treatment for a sleeping disorder, so the results seen here don't necessarily apply to the rest of us. Second, researchers still can't be sure of what exactly is going on inside someone's head while they're asleep, so it's possible that these volunteers were acting out dreams without actually dreaming. As Neuroskeptic says over at Discover, it brings into question what the definition of a dream actually is:
"Is it simply a subjective experience during sleep? If so, how can be sure that these patients are dreaming? Maybe they are just behaving as if they are dreaming, but without any conscious content. Maybe non-dreamers are a concrete example of philosophical zombies (P-Zombies) - a hypothetical creature that behaves like a normal human, but has no conscious experiences."
Even with those caveats in mind, there's evidence here that we could be dreaming when we think we aren't, so you might want to set up a night-vision camera overnight before you label yourself a non-dreamer.