New paper in PNAS proposes unexpected relationship between language and habitat
On January 20, 2015 Proceedings of the National Academy of Sciences published a paper “Climate, vocal folds, and tonal languages: Connecting the physiological and geographic dots” linking some language aspects with native climate of its speakers. We have asked one of the authors of this research, Prof. Caleb Everett from University of Miami, to comment on this work.
This particular project began with a simple question: do variations in ambient air conditions impact how people make sounds? And the answer is, simply, yes. This answer was found by examining research carried out in the last decade and a half by laryngologists. They have demonstrated that very dry air has a negative impact on the way the human vocal cords operate. Experimental and naturalistic studies have demonstrated that such air, particularly really cold air with trace amounts of humidity, makes the human larynx operate less efficiently. (This comes as no surprise to singers.)
One of the several ways the vocal cords are impacted in really arid conditions, and in general when they are dehydrated, is that they vibrate together somewhat more erratically. So it is harder to make really precise pitches in desiccated contexts. This led me to a simple hypothesis tested in our paper: Should not languages that rely on precise pitch for the mere conveyance of meaning, languages with complex tone, be less likely to occur in very arid regions? To answer this question, Damian Blasi, Sean Roberts, and I analyzed two large, independently coded databases of the world’s languages. And we found that there is clear quantitative support for the hypothesis, even after carefully controlling factors such as relationships between languages. Languages with tone, and in particular complex tone, are significantly less likely to occur in the very dry regions of the world. In short, languages appear to be ecologically adaptive in this respect. Yet I should stress that we are not claiming that languages are simply determined by climate, or that languages with complex tone are never spoken in dry regions. What we are claiming is that, over the long term, there is a subtle pressure against the usage of sounds that are ecologically inefficient for biological reasons. This pressure may surface, for instance, in less efficient diffusion of words with complex tones across languages. (We do not claim that native speakers of tonal languages have any difficulty communicating in really dry areas.) It is possible that the effects of desiccated air impact languages in other ways, but that is unclear at present. For this study, we were simply testing what we considered to be a clear and reasonable hypothesis, which was based entirely on previous experimental work.
As someone who studies languages, I have wondered for some time why this ecological adaptability of our species would not extend to speech. Linguists (including myself) have generally assumed that speech is not ecologically adaptive. Yet it turns out we do not have very good reasons for this position. We know a lot about language change, and many of the reasons languages change have nothing to do with ambient air characteristics. But we actually do not have any strong empirical support for the standard position that languages are impervious to ecological effects. Quite the contrary, the evidence now accruing suggests speech is ecologically adaptive in subtle ways. And while some linguists may likely remain skeptical of this conclusion, biologists and physical anthropologists seem much less surprised by our claims. They are well aware that we are ecologically adaptive in pervasive ways, as are other species to varying extents.
As it relates to our specific hypothesis of ecological adaptability, we are examining other possibilities that relate to the effects of cold/dry air on the vocal tract. And we hope other researchers follow up on this work since it has clear implications for theories on the development of languages. More generally, I think our study is indicative of the tendency of researchers to consider more carefully the ways in which language interacts with other aspects of the human experience. Increasingly we are paying attention to the ways that putatively external cultural, cognitive, and biological factors both affect and reflect the incredible variation we see in the world’s languages. Many linguists have come to believe that, to truly understand language, we need to consider how it impacts and is impacted by other facets of our lives. Methodologically, our study is indicative of another shift underfoot: The shift towards the usage of quantitative methods familiar to other fields. Young language researchers like my co-authors are trained with traditional linguistic tools, but also increasingly trained in advanced quantitative methods that allow them to tackle issues in new ways.
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