Decades after his comedy sketch, Stephen Fry visited Gleason in Boston for a documentary series about language. “We went down to the local school and sat down with the children and did the test. They weren’t very cooperative that day but he was a lot of fun,” she says.

To Gleason’s surprise, even very young children – around three years old – already had a firm grip on grammar. They could easily tell her that a man had “spowed” the day before or that they were, in fact, looking at two “wugs”.

The tricky ones were those which already had these “s” or “d’ endings, such as the past tense of “bod”, which they didn’t learn to express by saying ‘bodded’ until much later. In Gleason’s made-up world, bodding is the practice of dangling an object on a string.

“It wasn’t that children learned these rules in different interesting ways; they basically all learnt the most common, simple cases first,” says Gleason. Regardless of intelligence, economic background or parenting, they all learnt the same skills at the same ages, in the same order, in the same way.

Today The Wug Test has been translated into numerous other languages, copied hundreds of times and is widely renowned as a classic. Intriguingly the same patterns – such as learning plurals first – are repeated in other languages too, such as Gleason’s native Hungarian. “Children learn to speak in a very, very regular way,” she says.

Alien languages

But where do the rules of the languages themselves come from? Why is it that English usually adds an “s” to make a plural or an “ed” to talk about the past? Grammatical rules vary so widely between languages, the particular details cannot be hardwired in our genes, yet we clearly pick them up very quickly.

Some clues come from another nonsense experiment, by Kirby and a team of scientists from the University of Edinburgh. “There are these two unique things about language: this unique structure which allows us to talk about things we’re never talked about before and that we learn it from our parents,” he says. They had a hunch that the two might be related.

To study how languages acquire their logic, they could have looked to any language on the planet – since they all have these features – but they are all big, complicated and take years to learn. The scientists needed something simpler. So they decided to make one up.

“We call it an alien language, mainly because it sounds exciting so gets people to sign up for our experiments,” says Kirby. They used computers to generate random strings of syllables and assigned a meaning to each new word. In one version, the words described exotic fruits the team had invented.

“There was nothing there – it wasn’t even a language, really. It was just a complete soup of words with these complex meanings,” says Kirby.