Many people think that animals dream. There is even some evidence to suggest that they do. But we don’t know for sure. Unlike people, animals can’t tell us when they’ve had a dream.

In people, there are five stages of sleep that make up one sleep cycle. The fifth stage is called rapid eye movement (REM) sleep. There is a close link between dreaming and REM sleep. Animals have something that looks like REM sleep. It is called “paradoxical sleep.”

You may see an animal whimper and twitch during sleep. This tends to occur during paradoxical sleep. It is paradoxical because it seems to present the following contradiction:

• The animal appears to be asleep.
• Brain waves and eye movements make it look like the animal is awake.

In the 1970s Adrian Morrison and other scientists studied paradoxical sleep. They also looked at how the brain causes “atonia.” Atonia is when the muscles are relaxed and still. This is the state your body is in during sleep.

The areas of the brain that control movement are very active during paradoxical sleep. Morrison caused small wounds to parts of the brainstem that control movement in cats. This led to a big change in their behavior during paradoxical sleep.

Normally cats are relaxed and lie on the floor of their cages as they sleep. But the cats with wounds to their brainstems were active during paradoxical sleep. They would move around their cages. It seemed that they were exploring or stalking a prey that was not there.

Dr. Morrison presented the findings of his research at the annual conference for sleep specialists. He even showed a film of the cats’ behavior. He said that the cats were in a state of “paradoxical sleep without atonia.” Many in the audience were convinced that the cats were acting out their dreams.

In the 1980s Carlos Schenck and Mark Mahowald at the University of Minnesota described a new parasomnia. It is called REM sleep behavior disorder (RBD).

People with this sleep disorder act out their dreams. They move around the bedroom, doing such things as shouting, kicking, punching, crawling or running. When they wake up, they tell about a dream they just had. Their actions match the story they describe from the dream.

RBD looks very much like paradoxical sleep without atonia. While Dr. Morrison’s cats were unable to speak, people with RBD are able to tell about their dreams. This helps to explain what would seem to be very strange behavior.

You can decide for yourself if you think that RBD and paradoxical sleep without atonia are the same. If you think they are, then you will most likely accept the idea that animals dream.

I became convinced of this when my daughters adopted a greyhound named Ginger. She had just been retired as a racing dog from a nearby track. During sleep Ginger often would start moving her legs like she was running. She also would breathe hard and whimper. After a few minutes she would sigh and relax.

I think Ginger dreamed of racing. I also suspect that other dogs dream of chasing cats and that cats dream of chasing birds.

By Dr. Richard S. Rosenberg
Updated August 25, 2006