And Tigger spots a strange black cat on a nearby roof.

And listen to this.

Chittering may simply be a sound of frustration but no one's really sure.

Rocky, out for a stroll in the afternoon...

Makes this noise when another cat blocks his way.

But the story of cat communication is a lot more surprising than this.

There's one noise we've hardly heard.

It rarely happens when the cats are out with each other.

Hello.

To understand what's going on...

Do you want some dinner?

We have to go back to the beginning and the youngest members of the study.

Biologist Dr John Bradshaw can explain why these one-week-old kittens meow.

The meow starts off as a kitten vocalization.

It's something that kittens use in order to call their mothers over and, as you can see, it's very effective in doing that.

The mother is very attentive to those meows.

And then, as the kitten grows up, it gradually stops meowing, presumably just because the meow stops working.

The mother wants to wean the kitten and stops responding.

With a pet cat, which is constantly meowing at its owner, it's a way of getting the owner's attention.

And that's because we are not very vigilant creatures.

We spend a lot of our time with our noses buried in books, or computer screens, or TVs, and a cat... each cat learns independently, we think, that using this piece of kitten behaviour is a good way of getting our attention.

So, meowing is a good way of getting us to look up and find out what it is they want from us.

There you go, Henry.

Come and say hello to Mummy!

So, cats have two different languages, one for each other... and one for us.

Scientists have found cats make a huge range of meows... and they wondered if there was a universal cat-human language.

Okay.

There's a trill that Jasper does, which is quite...

Yeah, that's it.

They make that funny little noise, they go...

-That doesn't sound anything like it. - think it does.

Scientists have discovered that every cat's meows are unique.

Each cat learns which noises work best in certain situations, developing a special language that only their owner will understand.

When they want food, it's a much more prolonged meow.

Are you hungry?

Miss Piggy's learnt how to say milk, so she does a proper milk meow.

She's like milk... like that.

Come on. Is it nice?

And when our cats meow, there's one thing that almost every owner in the study said they did.

Did you go hunting today?

Talk back.

Pretty girl. Are you a pretty girl? Are you Momma's pretty girl?

Pixie, you lovely girl. Yes!

Talking comes naturally to us and every kitten that spends time with people learns that to communicate with us, they have to make a noise.