You've probably seen it happen—your sleeping dog suddenly lets out a woof as his legs begin to twitch. Is he dreaming?
Many scientists say there is evidence to support the idea that dogs do, in fact, experience dreams. Researchers using an electroencephalogram (EEG) have tested canine brain wave activity during sleep. They've found that dogs are similar to humans when it comes to sleep patterns and brain wave activity. Like humans, dogs enter a deep sleep stage during which their breathing becomes more irregular and they have rapid eye movements (REM). It is during REM sleep that actual dreaming and, often, involuntary movements take place. Dogs may move their legs as if they are running, whine or whimper as if excited, and breathe rapidly or hold their breath for short periods.
Not all dogs dream equally. Research suggests that small dogs dream more than larger dogs. A Toy Poodle may dream once every ten minutes while a Golden Retriever may only dream once every 90 minutes. Dreaming also seems to occur more frequently in puppies. This may be because they are processing huge quantities of newly acquired experiences.