The Science Behind Dreams

This content was created by the National Sleep Foundation

Most people can recall at least one good and one bad dream they’ve had over the course of their lives, but why they had those dreams—and what they mean—is a subject of ongoing debate in the scientific community.

Experts generally agree that a dream is a series of subconscious images that occur during sleep and can include sounds, sights, and other sensations. Dreams occur most frequently during rapid eye movement (REM) sleep, a deep sleep state that means you are less likely to be disturbed.

But as for the significance of dreams, and why people remember some dreams and not others, there is much research still to be done. Discover what we do—and don’t—know about the thoughts and images we experience during sleep.

Why We Remember Some Dreams

Because REM is a deep and powerful sleep state, it may explain why suddenly awakening during this time makes a dream feels especially vivid. Dreams that occur during REM may also be more memorable because they are typically longer: Early in the night, dreams only last a couple of minutes but they increase in length as you get more REM sleep. Another theory suggests that dreams are the result of a “data dump” for the brain; it processes important events of the day (experienced as dreams) and deletes insignificant memories.

Why Dream?

Scientists aren’t entirely sure why we dream, but ongoing research is using neural imaging to find relationships between dream contents and brain activity patterns. One thought is that the hippocampus (which controls memory) works with the neocortex, which controls higher-level thought, to create meaning out of all the information your brain has collected, which may be experienced as dreams.

Some scientists believe that dreaming is related to signals sent to the cortex during sleep. Some of these signals are crucial for memory and learning, but some are seemingly random. Your brain might try to interpret these signals by combining them into a cohesive story, resulting in a dream.

The Meaning Behind Dreams

Although research is ongoing, dreaming in REM sleep might be a coping mechanism to help process emotions, thereby helping you to develop cognitive capabilities. That could explain why you have certain dreams when you’re stressed out, or why you might dream frequently about an important person in your life.

Your dream contents may vary in intensity and bizarreness depending on whether you’re in REM sleep, in non-REM sleep, or taking a nap during the day. In REM sleep, your dreams are more likely to have emotional significance and a higher sensory experience, and they may be a little bit stranger than NREM dreams. You’re also more likely to recall your dreams after naps rather than after a full night of sleep.

Of course, it’s possible that some dreams are just about wish fulfillment. This includes your standard flying dream relating to a desire for freedom, or a dream about driving relating to a concern about your life’s direction. But while it’s fun to speculate about a dream’s meaning, remember: Sometimes, a dream is just a dream.