This is Hidden Brain. I'm Shankar Vedantam.

There's a video on YouTube you might have seen.

It has nearly 200 million views.

In this video, a pair of twin brothers are standing in a kitchen, having a little chat.

These twin brothers

are diaper-clad babies.

Now, if this video featured 10-year-old twins or adult twins, I guarantee you it wouldn't have gone viral.

What makes this video special is that we have no clue

what these babies are saying. To us non-babies, it sounds like gobbledygook. Cute,

mysterious, gobbledygook. Here at Hidden Brain, we love trying to understand the puzzles and contradictions of human behavior.

But we spend most of our time talking about the older members of the human race.

Today, we focus on the younger set.

The much younger set. I find babies are so impressive. We can't really ask them what they're thinking. We have to come up with clever ways of figuring out what's going on in their little brains. We'll meet some of the researchers trying to decipher the behavior of babies. Oh, oh, that's a ball. Yep, you're right. Do babies understand us when we're talking to them?

That's a ball. You tried to say ball. That's great.

And how babies communicate even if they don't have words.

The Language of Babies This Week on Hidden Brain. brain.

Hi, I'm Laura Sirelli.

When Laura was in college, she spent her summer vacations back home in Sabre, Ontario.

Like five hours north of Toronto.

And she worked at the magical nook, a daycare center.

It was a large center that had different age groups, so there was like a baby room and a toddler room, preschool or school-age children, probably about 100 children total, but my favorite room was

the toddler room for sure.

...