Why Do We Dream?

Every night, you probably spend about two hours dreaming, even if you can't remember a single dream in the morning. Most dreams happen during a stage of sleep called REM, which stands for "rapid eye movement". In this stage, your eyes move quickly under your eyelids, your brain is almost as active as when you are awake, and the muscles in your body are relaxed so that you don't act out your dreams.

But why do we dream at all? The honest answer is that scientists still aren't sure. There are several theories, and the truth might be a mix of them.

One popular idea is that dreams may help us to remember. During sleep, the brain sorts the information it collected during the day. It keeps what is important and deletes the rest. Dreams could be a side effect of this process, which would explain why we often dream about people and places from the day before, mixed up in strange ways.

Another theory says that dreams might be a kind of training. In a dream, we can face danger without real risk: we run from monsters, fail exams or miss trains. Some researchers think this may prepare us to react better to problems in real life.

A third idea is that dreams help us deal with emotions. People who have had a difficult day often have more intense dreams. Studies suggest that during REM sleep, the brain can review painful memories in a calmer way, so they may feel less painful the next morning.

What about dreams that seem to predict the future? Scientists say they can't be magic. We have thousands of dreams, so a few of them will match real events just by chance. And dreams about falling or losing teeth must be very common, because people all over the world describe them.

One thing is certain: sleep matters. If you don't get enough of it, you will probably feel tired, forget things and get angry more easily. So tonight, go to bed a little earlier. Your dreams might be doing important work.