by Stephanie Pappas:We only remember a fraction of our dreams, and even those slip away if we don’t try to remember them—here’s why.

Dreams-awaken

If you’ve ever awoken from a vivid dream only to find that you can’t remember the details by the end of breakfast, you’re not alone. People forget most of the dreams they have—though it is possible to train yourself to remember more of them.

Dreaming happens mostly (though not always exclusively) during rapid eye movement (REM) sleep. During this sleep stage, brain activity looks similar to that in a waking brain, with some very important differences. Key among them: during REM sleep, the areas of the brain that transfer memories into long-term storage—as well as the long-term storage areas themselves—are relatively deactivated, says Deirdre Barrett, a dream researcher at Harvard Medical School and author of the book The Committee of Sleep (Oneiroi Press, 2001). This may be a side effect of REM’s role in memory consolidation, according to a 2019 study on mice in the journal Science.

Short-term memory areas are active during REM sleep, but those only hang on to memories for about 30 seconds.

“You have to wake up from REM sleep, generally, to recall a dream,” Barrett says. If, instead, you pass into the next stage of sleep without rousing, that dream will never enter long-term memory.

REM sleep occurs about every 90 minutes, and it lengthens as the night drags on. The first REM cycle of the night is typically just a few minutes long, but by the end of an eight-hour night of sleep, a person has typically been in the REM stage for a good 20 minutes, Barrett says. That’s why the strongest correlation between any life circumstance and your memory of dreams is the number of hours you’ve slept. If you sleep only six hours, you’re getting less than half of the dream time of an eight-hour night, she says. Those final hours of sleep are the most important for dreaming. And people tend to remember the last dream of the night—the one just before waking.

Other factors also contribute to whether you’ll remember your fantastic nighttime adventures, Barrett says. Women tend to remember a few more dreams than men, on average, according to a 2008 meta-analysis of multiple dream studies. Young people remember more dreams than older people, multiple studies have shown. Memory of dreams increases in kids from the age at which they can communicate about those dreams, plateaus from the early teens to the early 20s and then very gradually declines in adults over the rest of their life span, Barrett says.

There is a lot of individual difference in dream memory, though. Some people almost never remember a dream, and others regularly recall several each night. People who are more introverted and inward-focused tend to remember more dreams, Barrett says, while those who are more extroverted and action-oriented tend to remember fewer. Imaginativeness and susceptibility to hypnosis are also linked to dream recall, as are some measures of creativity, she says, though creativity is tricky because not all measures of creativity even line up with one another, much less with dream tendencies. Overall, according to one 2017 study, recall of and interest in dreams seems tied to openness to experience, a personality trait characterized by a desire to try new things and explore unusual ideas.

A few studies that have investigated lucid dreaming—vivid dreams the dreamer remembers very well and feels in control of—suggest that some areas of the brain linked to attention are more active in people who recall more dreams, indicating that basic neurological differences may play a role.

“Some people don’t pay as much attention to their dreams while they’re happening as others, just in terms of brain action going on,” Barrett says.

It is possible to train your brain to remember more of your dreams, though, says Leslie Ellis, a clinical counselor in British Columbia and author of A Clinician’s Guide to Dream Therapy: Implementing Simple and Effective Dreamwork (Routledge, 2019). She advises clients who want to remember their dreams to take a moment when they wake up, before they even move their body, to think about what they were just dreaming and remember as much as possible. This moves the dream from short-term memory to long-term memory.

“Write it down right away, and then you’ll have it there,” Ellis says, “because they do slip away unless they’re deliberately recorded, for most people.”

Dreams are often considered nonsensical in Western culture, Ellis says. Though the narratives may not make much sense, they often hint at emotions that people are processing in their waking lives. “We do dream about the things we kind of don’t want to look at,” she says. “During the day, we can repress a lot of that, but the dreams will bring those things to the surface.”

Even just thinking about dreams more often can bring them more fully into your waking life. Taking a class on dreaming, reading a book about dreaming or even just thinking more about dreaming has a short-term impact on people’s dream recall, Barrett says.

“Trying to remember your dreams or even just having a lot of context with references to dreams will temporarily increase your dream recall,” she says. “You can do it on purpose…. But it [also] indirectly works if somebody’s been talking to you a ton about dreams or you read an article in a magazine today on dreams.”

In other words, if you’ve made it to the end of this article, you may have sweet dreams tonight.

Stephanie Pappas is a freelance science journalist. She is based in Denver, Colo.