In trying to understand the cultural evolution of language, scientists have observed that small, isolated linguistic communities often develop languages that have complex structures, elaborate and opaque morphology, rich patterns of agreement, and many irregularities.
It has also been suggested that such features of languages require long interactions in small, close-knit societies to develop.
By contrast, languages with large communities of speakers, such as Mandarin or English, appear to be structurally simpler.
But an apparently opposite pattern appears in relation to non-structural properties, such as word usage: languages with many speakers tend to have larger vocabularies. English, for example, has grown rapidly and is estimated to have many hundreds of thousands of words, including those with highly specialised and technical meanings.
Despite their frequent structural complexity, languages spoken by small numbers of speakers are typically assumed to have smaller vocabularies.
An analysis of Polynesian languages indicates, moreover, that larger linguistic communities both create more new words and lose fewer existing words over time.
These contrasting patterns pose a challenge for theories based on the cultural evolution of language.
Why does the size of a population of speakers have opposite effects on vocabulary and grammar?
Through computer simulations, a team of cognitive scientists at Cornell University in the US has have shown that ease of learning may explain the paradox. The research suggests that language, as well as other aspects of culture, may become simpler as the world becomes more interconnected.
“We were able to show that whether something is easy to learn – like words – or hard to learn – like complex grammar – can explain these opposing tendencies,” says co-author Morten Christiansen.
The researchers hypothesised that words are easier to learn than aspects of morphology or grammar. “You only need a few exposures to a word to learn it, so it’s easier for words to propagate,” Christiansen explains.
But learning a new grammatical innovation requires a lengthier process, and that’s going to happen more readily in a smaller speech community, because each person is likely to interact with a large proportion of that community.
“If you have to have multiple exposures to, say, a complex syntactic rule, in smaller communities it’s easier for it to spread and be maintained in the population,” he says.
Conversely, in a large community, like a big city, one person will talk only to a small proportion the population. This means that only a few people might be exposed to a new complex grammar rule, making it harder for it to survive.
This mechanism can explain why all sorts of complex cultural conventions emerge in small communities: for example, the slang that developed in the intimate jazz world of 1940s New York City.
The simulations suggest that language, and possibly other aspects of culture, may become simpler as our world becomes increasingly interconnected. Christiansen says: “This doesn’t necessarily mean that all culture will become overly simple. But perhaps the mainstream parts will become simpler over time.”
Not all hope is lost for those who want to maintain complex cultural traditions, however. “People can self-organise into smaller communities to counteract that drive toward simplification,” he says.