What is Rapid Eye Movement?

Mary McMahon
Mary McMahon

Rapid eye movement (REM) is a physiological phenomenon which occurs during stage five sleep, the part of the sleep cycle when people dream. Some people refer to this stage of sleep as REM sleep, in a reference to the physiological markers which can be used to identify it. The earliest research on rapid eye movement was done in the 1950s in Chicago by Nathaniel Kleitman and Eugene Aserinsky, and the two revealed a number of interesting things about the sleep and cognition with their research.

A woman during Rapid Eye Movement (REM) sleep.
A woman during Rapid Eye Movement (REM) sleep.

Humans are not the only animals to demonstrate rapid eye movement. Birds and other mammals appear to have REM cycles in their sleep as well. The younger an animal is, the more time it spends in REM sleep; babies, for example, can spend up to seven hours a day in REM sleep. The exact function of this stage of sleep is not fully understood, although scientists have a couple of hypotheses.

Birds are believed to have REM sleep cycles.
Birds are believed to have REM sleep cycles.

As you might imagine, rapid eye movement is characterized by jerky movements of the eyes under the lids. This movement is totally involuntary, and it is typically accompanied with a still body, as the brain appears to block the neurotransmitters which allow muscles to move during REM sleep. While in REM sleep, people often have vivid and distinctive dreams which they remember when they wake up; researchers who have interrupted REM sleep often get subjects to recall up to 80% of their dreams, and these researchers have also noted that the subjects make up for the interruption with a long phase of rapid eye movement sleep.

While in REM sleep, people often have vivid and distinctive dreams.
While in REM sleep, people often have vivid and distinctive dreams.

There are five distinct stage in sleep, which are repeated over and over again. A complete cycle takes around an hour and a half, which has led some people to suggest that sleep should occur in increments of an hour and a half; in other words, six hours of sleep may actually be better than seven. The first four stages of sleep start light and get progressively deeper, with brain waves slowing dramatically. In the fifth stage, REM sleep, the brain gets extremely active, almost like the sleeper is awake.

The rapid eye movements associated with this stage can be used to identify it, but researchers can also identify REM sleep patterns by using machines which measure brain activity. The signature of REM sleep is quite distinctive, and recognizable to many sleep researchers. It is believed that this phase of sleep may allow the brain to consolidate and process memories, and it may also be a resting period for the mind, allowing it to recharge after a busy day.

Babies can spend up to seven hours in REM sleep.
Babies can spend up to seven hours in REM sleep.
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

You might also Like

Readers Also Love

Discussion Comments


I remember being terrified when I saw my little brother's involuntary rapid eye movement. I was only four at the time, and he was two, but I knew nothing about REM, so I thought something was eating his eyeballs from the inside!

I ran crying to my mother, who had to try and explain REM sleep to a panicking four-year-old. After she had told me about it, we went back in the room together and watched him sleep.

I think seeing her reaction to his REM made me feel better. If she could see his eyes moving underneath his lids like that and not be worried, then I knew it must have been fine. Sometimes, reactions to situations are greater proof than explanations of them.


Some people say that animals can't have dreams, but I think that if a creature is capable of having rapid eye movement, then dreams are occurring in their minds. I've observed this with my dogs, and it is a strange sight to see.

Dogs don't have eyelids like ours. They have a semi-transparent membrane that closes over their eyes, and they then are able to close the gap where their eyes are. If you watch one closely as it sleeps, you can see the eyeballs moving underneath their flesh surrounding their eyes.

Their eyes aren't the only thing that moves, though. I've also seen their lips and noses twitching involuntarily, and sometimes, they whine, growl, and even try to run in their sleep!


@orangey03 – Since you wake up a lot, you are probably not even getting enough non-rapid eye movement sleep. A lack of one affects the other, since you have to go through the first to get to the last.

I have heard that REM stages get longer as the night goes on. If you were able to sleep through the whole night, you would probably be able to remember a lot more of your dreams, and you probably wouldn't feel so irritable, either.

I tried setting my alarm for just half an hour later than I normally got up, and it made a big difference. Since my REM sleep was more intense in the early morning, I got more of it and felt like I had more of my inner issues resolved when I woke up. So, if you can, you might try sleeping just thirty minutes more than you usually do.


I tend to have little snippets of dreams that I can barely recall. I wake up a lot during the night, and even though I do sleep, I don't feel rested the next day.

I actually feel tired all the time. I am also extremely cranky, and I've been asked why I'm so irritable.

Could it be because I'm not getting enough REM sleep? I thought that since I had bits and pieces of dreams, I must be getting some, but maybe some is not enough.

Post your comments
Forgot password?