Creating language: Integrating evolution, acquisition, and processing by Morten H. Christiansen and Nick Chater (review)

"How do you get to Carnegie Hall? Practice, practice, practice." (Anonymous)

According to Christiansen and Chater (2016), a goal of this book is to bring together the study of language evolution, acquisition, and processing. To do this, they argue that it is necessary to move beyond what they call "Chomsky's hidden legacy" (p. 6), which in their view is responsible for the separation of these fields in the first place. But it is not just Chomsky that they are attempting to transcend; it is the whole of what they call mainstream linguistics. A central thesis advanced here, signaled by what is missing from the subtitle, is that evolution, acquisition, and processing can profitably be studied in the absence of an account of grammar. Moreover, the "overarching framework for the language sciences" (p. 17) that they propose jettisons long-held theoretical distinctions such as competence versus performance, acquiring knowledge of language versus learning a skill, and language evolution versus language change.

These radical– and in my view, misguided–proposals are the main subjects of this review. However, I do not want to give the impression that Creating language consists entirely of anti-generative polemics. The book is divided into two parts, "Theoretical and empirical foundations" and "Implications for the nature of language". In the first part, the authors present their views on how the three fields in their title (evolution, acquisition, and processing) interact, drawing attention to the vastly different timescales over which they operate. The second part presents the results of research by the authors and their colleagues on aspects of language acquisition and processing, and experiments on learnability. These sections rest on a substantial body of work: by my count, the authors have contributed, either individually or together, to 90 publications in the reference list. These results will be of interest to those who work in these areas, and they deserve more discussion. However, the constraints of space compel me to stick to the wider issues.

The authors adhere to the theory that language is a "parasite" (p. 43, a "beneficial" one, thank goodness) that has adapted to our brains over years of cultural evolution: "Language is easy for us to learn and use not because our brains embody knowledge of language, but because language has adapted to our brains" (pp. 20–21, emphasis in the original text). There is thus no need for separate theories of language evolution and language change, because language evolution is just the result of language change over a long timescale. To illustrate how this evolution might work, the authors discuss learning simulations they ran using connectionist Simple Recurrent Networks that were exposed to miniature languages generated by simple grammars with no fixed word-order constraints. The best-learned languages in each generation were the basis for the languages provided to the next generation. After less than a hundred generations, the resulting language had adopted consistent word order.

Belief in a distinction between language evolution and language change, however, is not "a side-effect of a theoretical position that is no longer tenable" (p. 240), but is based on the empirical observation that language change does not work like the authors' simulations. If the authors are correct, we should find that every language becomes simpler and easier to learn and use over time. This has not been shown. Apart from cases where a language has undergone simplification in some respect (simplification being a common type of language change), the only examples that the authors adduce in support of their hypothesis are Nicaraguan Sign Language and Al-Sayyid Bedouin Sign Language. But these are not examples of ordinary language change; both have recently developed into full-fledged languages from something less than that. It is telling that the authors do not point to any of the well-documented cases of languages changing over hundreds and even thousands of years. These cases show that languages change, but do not...