Watching a sleeping dog's legs paddle or hearing a soft muffled bark is one of the more charming things about living with one, and it's not just imagination. Dogs cycle through the same broad sleep stages humans do, including REM sleep, the stage most associated with dreaming.
What the research actually shows
Studies on sleeping rats, whose brain activity is easier to record in detail, found patterns during REM sleep closely matching activity recorded while the rats ran a maze while awake, suggesting a kind of memory replay. Dogs show similar REM patterns, and researchers generally believe something comparable is happening, replaying the day's activity, even if we can't know exactly what a dog experiences.
Frequently asked questions
Should I wake my dog up if they seem to be having a bad dream?
Generally it's better not to. Waking a dog abruptly during a dream state can startle them into a confused or even snapping reaction before they're fully oriented, more so than letting the episode pass on its own.
Do puppies dream more than adult dogs?
Puppies do spend more total time in REM sleep than adult dogs, which lines up with twitching and vocalizing seeming more frequent and pronounced in younger dogs.
Is heavy twitching during sleep ever a medical concern?
Normal dream-twitching is typically brief and stops easily if the dog is gently roused. Prolonged, rigid, or seizure-like episodes that don't respond to a light touch or voice are different and worth a vet call.