DAVID POGUE: At the University of Chicago, neuroscientist Peggy Mason is about to show me that empathy might not be just for humans.

PEGGY MASON (University of Chicago): Are you going to be empathic today? Yeah.

DAVID POGUE: To test her idea, she's built a special predicament for two rats: one is trapped inside a Plexiglas tube, with a door that can be opened only from the outside. The other is free to run around, and he's never been taught how to open that door.

So you think that Free Rat is literally trying to set free Trapped Rat out of pure human concern.

PEGGY MASON: Or rat concern, as the case may be.

DAVID POGUE: Unbelievable. Look at that! He's trying to figure it out. What the heck.

Oh, my gosh.

And when they see their pal struggling, they certainly seem to work pretty darn hard to get their buddy out.

PEGGY MASON: He is pulling him out.

DAVID POGUE: Come on! He's like, "For crying out loud, I got you out, now bust out of here!.

Mason has run hundreds of rats through these set ups, and she's convinced it's the strongest experimental evidence, to date, of animal empathy.

PEGGY MASON: So, it's the first experiment where there's an action that is motivated by empathy. They're using empathic concern to actually help the other rat.

DAVID POGUE: So just how much do these rats really care? Mason wanted to find out, so she did a second experiment to give these rats a moral dilemma.

PEGGY MASON: What we did was we put two restrainers in the arena. And in one restrainer was the cage mate, and in the other restrainer was five chocolate chips. And these are rats that were eating, on average, seven chocolate chips in a sitting, so five chocolate chips, no problem.

DAVID POGUE: What will the free rat do? Will he hog all the chocolate to himself? Free the friend.

So, in theory, we've given Free Rat a choice.

PEGGY MASON: That's right.

DAVID POGUE: He can either let his pal out of the tube or go get a nice tasty snack. Hmm, checking out his pal. Oh, come on! He let the guy out first. Incredible.

Whoever gets there first is going to gobble it all up.

PEGGY MASON: Will they? Or will they share.

DAVID POGUE: They not smart enough to share. They're rats.

PEGGY MASON: They're nice, they share. So, on average, the free guy only eats three and half chocolates. There's five chocolates, so he's leaving one and half chocolates.

DAVID POGUE: I might have to think twice the next time I want to call someone a rat.

PEGGY MASON: Our study tells us a lot more about humans than it does about rats.

DAVID POGUE: Come on you guys! Somebody.

PEGGY MASON: And what I think it tells us about humans is that we are biologically mandated to be empathically concerned and helping.

BRIAN HARE: The more we're studying animals, what we're seeing is pieces of the moral system that we see in our own species. Now, no species has the whole package, but it basically tells us that our psychology, our brain, it didn't just appear out of thin air. It's actually built on something.

DAVID POGUE: Hello, New Yorkers. What am I, an animal.

Yeah, I am, and as long as my species treats me like one, it seems like I'll be just fine.

Oh, my gosh. Thank you very much! Elvis, ladies and gentleman.