From time to time people ask me if nonhuman animals (animals) dream. Just this morning I received an email from Canada's Discovery Channel flagship science and technology show "Daily Planet". I was asked to comment on a video of an English bulldog puppy dreaming and to answer a few questions on dreaming in animals.
I feel confident claiming that all mammals dream but this does not mean that other animals do not dream. We really just don't know if they do or not and we should keep the door open about this very challenging question. Charles Darwin's ideas about evolutionary continuity note that the differences among various species in anatomy, physiology, behavior, and emotions, for example, are differences in degree rather than kind. This basically means that the differences are shades of gray and not stark, black and white, variations. So, following up on Darwin, I like to say, "If we have or do something, 'they' (other animals) have or do it too."
Science shows that animals do indeed dream
All mammals share the same neural structures that are important in sleeping and dreaming. Innumerable people have seen dogs twitching and often vocalizing in their sleep and say they're sure they're dreaming. While some people dismiss these "citizen accounts" as mere stories, there are solid scientific data that clearly show that other animals do indeed dream.
In research conducted at the Massachusetts Institute of Technology (MIT) rats have been shown to dream about previously running a maze (see also) and researchers have also discovered that they have complex dreams. To quote from an account of this research, the "rats were hooked up to a device that measured the pattern of neurons firing in the hippocampus, an area of the brain known to be involved in memory. The scientists had the rats perform specific tasks in a maze which produced very distinctive brain patterns. When they repeatedly saw almost exactly the same patterns reproduced during sleep, they concluded the rats were dreaming about running through the maze. The correlation was so great that scientists said they could place where in the maze the rat was dreaming it was — and even if it was dreaming of running or walking."
More recent research has shown that scientists can even control what the rats dreamed about (the abstract for the original research can be found here). (Please note that my writing about this does not mean I'm an advocate for using animals in invasive research or for what's being called "dream engineering".)
So, I'm sure that dogs, cats, hamsters, guinea pigs, mice, wolves, giraffes, zebras, lions, elephants, and many other animals dream but at the moment I'm not sure they are always dreaming when we think they are and it's difficult to know just what they're dreaming about. Maybe they're dreaming about playing with their best friends, a good meal or odor, a walk with their human friends, a scary situation, or anticipating a fun day sniffing here and there at the dog park. Future research will surely provide many answers to these very interesting and vexing questions.
Please stay tuned for more on the fascinating lives of the animals with whom we share our homes and other aspects of our lives.
The teaser image can be found here.