Most of us have dreams and remember the thoughts, images, and sensations that happened during them upon waking up. Then, there are others who claim they rarely dream, if they dream at all, as well as those who can’t ever seem to remember them. But according to a recent study, published in Journal of Sleep Research, self-proclaimed non-dreamers with REM (rapid eye movement) sleep behavior disorder might be dreaming more than they think, as they were found to make movements and sometimes even speak during their sleep. The researchers said these actions might correspond to the content of their dreams.

Most people over the age of 10 dream at least four to six times a night during REM sleep, according to the University of California, Santa Cruz. During this time, our brains become as active as they are during our waking hours, although not all parts of the brain are reactivated during REM periods, which last anywhere from five to 34 minutes, depending on which stage of sleep a person is in.There is also evidence we can dream during non-REM sleep, usually in the hour or two before waking up, when the brain becomes more activated than it was earlier in the night.

Study author Bastien Herlin, from the ICM Brain and Spine Institute in France, and his colleagues sought to test whether self-proclaimed non-dreamers aren’t actually able to dream. A total of 289 participants with REM behavior disorder — which causes the dreamer to lack muscle paralysis during REM sleep, therefore “acting out” parts of their dream — were given a questionnaire that asked whether they dreamed. Out of the participants, 2.7 percent reported they had not dreamed for at least 10 years, while 1.1 percent said they had never dreamed.

In many of these participants’ cases, however, their actions during sleep implied they were dreaming. For example, a 73-year-old participant claimed he used to recall dreams as a child but stopped at the age of 20. Meanwhile, in the sleep lab, he was talking, yelling, and moving his legs and arms, all while he was asleep. “[Videos show] the patient arguing, swearing profanities, kicking, boxing, and throwing items toward an invisible individual during REM sleep, as well as fighting again in another REM sleep episode one year after, with no subsequent dream recall despite the nurse’s immediate inquiry,” the authors wrote.

The researchers also recorded his speech patterns, which were translated from French: “What can I make to eat, I saw … You listen… (incomprehensible words, then high-pitched voice) Stay here before doing such a thing, you bitch!” This participant’s speech and actions are common in dream-like sequences, according to the study. Herlin believes “dreaming production is universal, while dreaming recall is variable,” and suggested there is no such thing as “non-dreamers.” But how can we be so sure?

Herlin’s research is limited because dreams are a subjective experience, meaning researchers can’t really know whether a participant dreams while they sleep — they can only assume the patients are dreaming based on their movements.

Discover Magazine suggests two concepts that refute the idea everyone dreams, as Herlin claims. First, while these participants may have behaved like they were dreaming, they may not have consciously been experiencing any of the dream images, sensations, and emotions that manifest from dreaming. Second, if the movements tied to REM behavior disorder are linked to a person’s dreams, then a person who never dreams would never make such movements. This means that someone with REM behavior disorder wouldn’t ever know they had it, because they wouldn’t have dreams to act out.

That said, the question remains: Do all of us dream? It depends on who you ask.

A 2003 study published in the journal Sleep Medicine found REM sleep can occur without dreaming. In a lab, self-proclaimed non-dreamers were awakened during the polysomnography (sleep test) in REM sleep. The findings revealed the group of non-dreamers could not recall any dreams after waking up during REM sleep. The researchers concluded, “These individuals might not experience dreaming.”

The inability to dream or recall dreams has been seen in people who suffer injuries in specific parts of the brain. These rare cases show that it is possible for sleepers to get the usual amount of REM sleep and not dream, while being mentally healthy. Basically, we can dream in REM or non-REM sleep, and it may be possible to have REM sleep without dreaming.

Sources: Herlin B, Leu-Semenescu S, Chaumereuil et al. Evidence that non-dreamers do dream: a REM sleep behaviour disorder model. Journal of Sleep Research. 2015.

Pagel JF. Non-dreams. Sleep Medicine. 2003.