The book is mostly a set of musings and proposals about what might be rather than proof or even hard statistics about the relationship between social / environmental factors and language structure.Peter Trudgill looks at why human societies at different times and places produce different kinds of language. He considers how far social factors influence language structure and compares languages and dialects spoken across the globe, from Vietnam to Nigeria, Polynesia to Scandinavia, and from Canada to Amazonia.
There was one thing in particular that I thought might interest people here though: he mentions a hypothesis from a linguist called Butcher that the typical sonorant heavy phonology of Australian languages is at least partly motivated by the historical high prevalence of middle-ear infections in Aboriginal children, which often result in some hearing loss. The book says the following:
According to Butcher (2006: 190):
This combination of vowel and consonant systems would appear to be unique amongst the world's languages. So, Butcher asks: what motivates and perpetuates the unusual phonemic inventories? He hypothesises that they may not be unconnected with the fact that chronic middle-ear infections develop in almost all Aboriginal infants, at a hugely greater rate than in any other population in the world, within a few weeks of birth, and that as a result about 70% of children have significant hearing loss. This loss affects the lower end of the frequency scale, but may also affect the upper end. Voicing contrasts rely on low-frequency acoustic cues. and friction and aspiration rely on cues at the high end of the spectrum. But Australian languages are "rich in contrasts which depend on rapid spectral changes in the middle of the frequency range" (2006: 205), which is precisely the range that is most likely to remain intact after chronic middle-ear infection. If such infections have been the norm for many generations, this would indeed provide a very plausible explanation for these unique phonological systems.These languages have as rich a system of sonorant consonants as any language in the world - and richer than most. This means that these systems have precisely the opposite proportion of sonorants to obstruents to that proposed as the normal tendency amongst the languages of the world (Lindblom & Maddieson 1988). A typical Australian language inventory may consist of 70% sonorants and only 30% obstruents. This implies that the perception of opposition within Australian phonological systems is heavily reliant on systematic differences in formant transition patterns at vowel-consonant boundaries.
Personally, I'm not sure how much I buy into this. It's true that the typical Australian language is sonorant heavy, but there are Australian languages that have fewer sonorants and have even developed new stop constrasts such as voicing. If large segments of the aboriginal population have or had difficulty perceiving those contrasts then it seems odd that new contrasts managed to arise. Perhaps the hypothesis could be tested by examining how the historical prevalance of ear infections varied across Australian, and looking for correlations between the historical prevalence and the sonorant to obstruent ratio.
