Why Do We Remember Some Dreams

October 16, 2018

If you’ve ever woken up on the brink of a heart attack, drenched in sweat and convinced you’ll never live down the shame of sprinting nude through downtown Pittsburgh, you know that some dreams are more memorable than others. Most dreams, in fact, seem totally unmemorable—at least in the sense that we can’t remember them. And yet every now and then a dream will linger into breakfast and well into the day, or month, or year—will become a memory like any other.

Why do some dreams stick with us, while the rest disappear? For this week’s Giz Asks we reached out to a number of neuroscientists, psychologists and sleep researchers to find out when, and why, we’re more likely to remember a given dream. As it turns out, we have a fairly good sense of what causes dream recall, as well as how to enhance it—so if you feel like you’ve been hemorrhaging dreams lately, read on for some good retention techniques.

Katja Valli

Postdoctoral researcher at University of Turku, Finland and senior lecturer in cognitive neuroscience at the University of Skövde, Sweden, whose research centers on altered states of consciousness and dream and sleep research

We usually recall only those dreams we had just before we wake up in the morning (or the middle of the night). This may be because during sleep, our brains do not seem to be able to transfer short-term memories into long-term memory, and thus dreams we had earlier in the night dissipate without leaving a trace. But lab studies show we dream in all sleep stages, across the night—we just need to be woken up to be able to recall the dreams.

The content of our dreams also affects what we remember. Very emotional, especially negatively toned dreams are better recalled than “mundane” dreams. This memory bias also exists for waking memories, and is not unique to dreams. Nightmares are often very well recalled, because they’re highly negative emotionally and they wake us up through being so frightening.

Some naturally have high dream recall, and remember their dreams almost every morning; others recall them poorly. This partly stems from interest in dreams: those most interested in their dreams also recall them better. Dream memory can be trained by paying attention to your dreams: start keeping a dream journal, and you’ll be surprised how many more dreams and how much more detail you can recall after few weeks.

“Those most interested in their dreams also recall them better.”

Shelby Harris

Clinical Associate Professor, Albert Einstein College of Medicine, and licensed clinical psychologist who specializes in behavioral sleep medicine

I like to think of dreaming as a way to figure out how to process all the information from the day. The brain is like a filing cabinet and, every night—especially during REM sleep—it is trying to make files to create memories, learn new skills and also figure out what papers to essentially shred. Dreaming is a jumbled up version of our daily lives, reflecting what’s going on as the brain attempts to encode the information and then store it away into the filing cabinet.

Most people struggle with remembering all of their dreams. Within the first five minutes of awakening, most people forget about 50% of them, with the remaining 50% gradually being forgotten over the next few hours as we begin the day.

Sometimes, we remember dreams simply because we wake up in the middle of them, if the dream was particularly distressing or upsetting, or if you’re more anxious or distressed.

Deirdre Barrett

Assistant Professor, Psychology, Harvard Medical School, and the author of The Committee of Sleep and The New Science of Dreaming, among other books

If we do not awaken immediately from a dream, it never makes it from our short-term memory into long-term storage. The most important neurotransmitter for this transfer—norepinephrine—is at a very low level during dreaming, as is electrical activity in the areas most important to long-term memory.

If we awaken straight out of a dream, we have some chance of remembering it. Even then, dreams are harder to recall than waking experience. This is partly because of their illogical, discontinuous, and sometimes vague events: one study found that less coherent dreams were harder for a listener to recall than ones with strong emotions and organized plot lines. The other issue is that, as the brain awakens, it is just starting to turn on areas necessary for long-term storage.

There are individual differences that predict dream recall. Getting plenty of sleep is the biggest determinant, and people who are more psychologically minded or specifically interested in dreams remember more. Looking at physiological differences, a 2014 study found that people with higher blood flow to the medial prefrontal cortex remembered more dreams.

There are techniques which can increase the number of dreams you recall. As mentioned, getting plenty of sleep is the most important one. Then, just as you are falling asleep, it is helpful to remind yourself that you want to remember your dreams. Let it be the last thought as you are drifting off. Keep a pad and pen by the bed or a phone with a dream recording app. When you first wake up, don’t jump up or even turn your attention to anything else.

Even if you don’t think you remember a dream take just a minute to see if there is any feeling or image you woke up with—sometimes a whole dream will come flooding back at that point. Reading and talking about dreams tends to increase recall of them. Even just reading this column is raising the odds that you’ll recall a dream tonight.

“One study found that less coherent dreams were harder… to recall than ones with strong emotions and organized plot lines.”

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