We were walking through the Wonderopolis pasture the other day when we overheard the following interesting conversation:

Pig: Hey Biff! How did you sleep last night? I had the weirdest dream.

Cow: Not bad, Patty. I had a weird dream, too. What was yours?

Pig: Um…well…I dreamed I was at a picnic and you weren't there and we were eating…

Cow: Yes? Eating what?

Pig: Well…we were eating cheeseburgers.

Cow: Yikes! What a nightmare!

Pig: What did you dream about?

Cow: It was sort of similar, I guess. I was at a picnic and we were eating…

Pig: What? What were you eating?

Cow: Bacon, lettuce and tomato sandwiches. And you weren't there either.

Pig: Oh my!

Duck: Hey you two! Did you get your invitation to the farmer's picnic yet?

Pig: No!

Cow: Me neither!

Duck: It's tomorrow and it looks like we're having bacon cheeseburgers!

Pig: Auuuggghhhh!

Cow: Run for your life!

We sure do feel sorry for Biff and Patty. Hearing their conversation got us to WONDERing. Do animals really dream?

If you've ever watched a dog sleeping, you probably thought to yourself that dogs must dream. A dog deep asleep will twitch and moan and “run" in its sleep, as if it was dreaming of running through a bone-filled field on a warm summer day. But can animals really dream like humans do?

As a matter of fact, scientists would agree with just about any dog lover you might ask. Dogs — and other animals — do indeed appear to dream much like humans do. But how do scientists know? Did they ask the animals in a series of interviews?

Of course not! Animals can't tell us about their dreams. We wish they could talk like they sometimes do in movies — or the Wonderopolis pasture — but scientists have to be more clever to learn what's going on inside animals' minds.

Researchers from Cambridge University used studies conducted at the Massachusetts Institute of Technology to conclude that animals do dream. In fact, they concluded that animals can have very complex dreams that include memories or replays of events that happened while they were awake.

The researchers studied rats that had been trained to run on a track. They mapped and measured brain activity with electrodes while the rats were awake and running.

They then did the same thing while the rats slept. They learned that rats experience rapid eye movement (REM) sleep like humans do. During REM sleep is when humans have most of their dreams. Scientists observed similar behavior in the rats they studied.

After comparing the data from when the rats were awake with the data from when they were asleep, they concluded that the data supported the view that the rats had replayed long series of waking events while they were asleep. In other words, they dreamed that they were running on the track!