Thursday, July 31, 2008

Cumulative cultural evolution in the laboratory: An experimental approach to the origins of structure in human language

Just as I finished the last post a link to this remarkable paper arrived in my inbox:

Cumulative cultural evolution in the laboratory: An experimental approach to the origins of structure in human language
Simon Kirby, Hannah Cornish and Kenny Smith

We introduce an experimental paradigm for studying the cumulative cultural evolution of language. In doing so we provide the first experimental validation for the idea that cultural transmission can lead to the appearance of design without a designer. Our experiments involve the iterated learning of artificial languages by human participants. We show that languages transmitted culturally evolve in such a way as to maximize their own transmissibility: over time, the languages in our experiments become easier to learn and increasingly structured. Furthermore, this structure emerges purely as a consequence of the transmission of language over generations, without any intentional design on the part of individual language learners. Previous computational and mathematical models suggest that iterated learning provides an explanation for the structure of human language and link particular aspects of linguistic structure with particular constraints acting on language during its transmission. The experimental work presented here shows that the predictions of these models, and models of cultural evolution more generally, can be tested in the laboratory.

I note that Ed Yong over at Not Exactly Rocket Science has already written a long post on it, so I won't write an elaborate post of my own (and Jonah Lehrer covers it too) But neither bloggers nor authors note the historical roots of the idea that languages might be subject to natural selection (the authors look-back horizon seems to be limited to John Maynard-Smith!)

Here is what Darwin wrote in the Descent of Man: there is a limit to the powers of the memory, single words, like whole languages, gradually become extinct. As Max Müller has well remarked:—"A struggle for life is constantly going on amongst the words and grammatical forms in each language. The better, the shorter, the easier forms are constantly gaining the upper hand, and they owe their success to their own inherent virtue." To these more important causes of the survival of certain words, mere novelty and fashion may be added; for there is in the mind of man a strong love for slight changes in all things. The survival or preservation of certain favoured words in the struggle for existence is natural selection.
(emphasis added by me)

What was it Marcus Garvey said (albeit in a different context): "A people without knowledge of their past history is like a tree without roots"! But all said and done, Darwin would have loved the paper!

In a similar vein see: 
Frequency of word-use predicts rates of lexical evolution throughout Indo-European history

And if you want a neat modern tree of Indo-European langauges, see the tree in this paper: 
Language-tree divergence times support the Anatolian theory of Indo-European origin

And as a takeaway project for readers, how many mistakes can you spot in this tree (published in Nature):

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