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Page last updated at 14:59 GMT, Tuesday, 10 November 2009

Unlocking the mysteries of speech

Man speaking

Animals may use sounds to communicate but talking is uniquely human. Yet despite decades of research scientists still haven't unlocked the secrets of speech. So why do we talk?

Talking is something most people do with such ease. We barely notice we are doing it, let alone stop to think how the brain processes the 370 million words an average person says in their lifetime.

Yet a complex sequence of thoughts, movements and actions lie behind each and every word we utter. And as adults, we speak 15,000 words every day.

Researchers have looked at babies brain waves

So where does language come from, how did this ability evolve and is it something we are born with or something we learn?

One scientist trying to unlock the secret of speech is Professor Simon Kirby, chair of language evolution at the University of Edinburgh.

He thinks the origin of language is the result of a "cultural evolutionary process".

"What's interesting about this process for language is just like in biological evolution, the thing that evolves shows this appearance of design," says Prof Kirby.

Horizon: Why Do We Talk? is broadcast on BBC Two at 2100 GMT on Tuesday, 10 November
Watch it on the iPlayer

"But just like we know in nature, there isn't a designer, it's just this process of evolution.

"Each speaker produces sentences that influence other speakers of the language, and that influences their children and so on over the generations. Somehow, out of this complicated soup of interactions between people, language emerges."

To explore how language develops and evolves over hundreds of years, Prof Kirby has created an alien language experiment that can be conducted in one afternoon.

The experiment consists of a series of made-up words used to describe alien fruits. Human guinea pigs have to familiarise themselves with new words which describe pictures of the fruits. They are then tested to see what they remember.


"In the beginning the alien words are completely random, with no common factors between them," says Prof Kirby.

"We start the experiment with this garbage language. In fact calling it a language is in some sense misleading, it's not even a language."

Early participants do very badly in the test because the language is completely random and unstructured. But there is a twist.

Watch the 'alien' language test in action

When they are tested, the experiment introduces some brand new fruits, so volunteers cannot possibly recall their names. Most people do not notice and invent words for the unfamiliar fruits.

Then for the next phase in the experiment, all the words produced by the first candidate are used to create the language for the next person.

"Each of these learners thinks they're giving us back the same thing that we trained them on as best they can, but in fact each of them unconsciously is changing that language, changing it piece by piece over time," says Prof Kirby.

As the alien language is passed through generations of users, it slowly turns from a random, chaotic one, to one of structure with combinations that can be easily remembered.


By the ninth generation, the words have been divided into parts and each of these has a different meaning.

"What we get at the end looks like a real language, not one we see in world today but it looks like a language in that it's got those essential defining characteristics. In other words, these languages that emerge are made up of parts that can be recombined," says Prof Kirby.

So the letters N, L and R describe different colours, the middle of the word different numbers and the end of the word like "plo" or "pilu" or "ki" describe the type of fruit.

alien language experiment
Prof Kirby has designed an 'alien' test to understand how language emerges

"This happens gradually, it happens without anyone knowing and yet it is the exact feature of language that makes it unique, makes language different from everything else in nature," says Prof Kirby.

"No one designed English, no one sat down and said it would be useful if it had relative clauses or grammar, it just happens, happens by this blind unconscious process of transmission. For the first time we're able to see that happening in the laboratory."

Because of our ability to combine sounds to make new meanings, how we talk will continue to change from generation to generation. And it's the fact language is a living entity that makes it so fascinating, but so evasive, for scientists.

Prof Kirby, and other scientists know, while they have come a long way, such discoveries are just the beginning of unravelling the mysteries of why we talk - and a glimpse of just how complicated the process is.

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