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?
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"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.

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.