It's impossible to know for sure if animals dream because, well, we can't ask them about their dreams. But if you've ever watched your dog whining and pawing in its sleep, you're probably convinced that at least some animals do. And new research is showing that way more animals than we initially thought might also dream.
Humans are most likely to dream during a sleep stage known as REM or rapid eye movement, which is what we involuntarily do during that stage. And other animals also have certain sleep stages where they'll move involuntarily. Cuttlefish flash different body colors and patterns.
Jumping spiders curl their legs up and down. And pigeons dilate and constrict their pupils. In fact, scientists have trained some pigeons to sleep in MRI machines and have found that during that stage of sleep, the bird's brain patterns seem to match those of dreaming humans.
So, while our ultimate dream of knowing exactly what's going on in a sleeping animal's head is still out of reach, it may soon come true.
