Whether they’re reliving childhood anxieties or visiting imaginary landscapes, most people dream. But there’s a small subset of the population who claims either to have stopped dreaming, or never to have dreamed at all. A group of researchers recently decided to look into the sleep patterns of self-proclaimed non-dreamers, to try to determine whether they may still be producing dreams. 

The researchers, whose study was published in the Journal of Sleep Research, recruited a unique group of participants. They wanted to look specifically at people who have REM sleep behavior disorder—a condition that causes people to act out their dreams. Because people with the disorder move around or speak in their sleep, their sleep patterns and behaviors are easier for scientists to observe. 

According to New York Magazine, four percent of the participants in the 289 person study said they never dreamed or hadn’t dreamed in over a decade. However, upon observation, many of them appeared to dream, moving, speaking, or reenacting imaginary scenarios in their sleep. For example, one participant in his 70s, who claimed not to have dreamed since his 20s, was observed arguing with, punching, and swearing at an invisible enemy as he slept. Upon waking, however, he claimed not to have had any dreams. 

The researchers recognize that the appearance of dream behavior is not definitive proof of dream production. More research is still needed to determine whether behaviors like sleep-talking and moving correspond to actual mental images. Still, the study provides strong initial evidence that non-dreamers may, in fact, be dreaming. 

[h/t New York Magazine]