Invited paper presented at the Workshop on Evolutionary Computation and Cognitive Science, Melbourne, Australia.
Across the languages of the world there is a high degree of consistency with respect to the ordering of heads of phrases. Within the Chomskyan approach to language these correlational universals have been taken to support the idea of innate linguistic constraints on word order. I will present an alternative explanation based on the suggestion by Christiansen (1994) that language has evolved to fit sequential learning and processing mechanisms existing prior to the appearance of language. These mechanisms presumably also underwent changes after the emergence of language, but the selective pressures are likely to have come not only from language but also from other kinds of complex hierarchical processing, such as the need for increasingly complex manual combination following tool sophistication. On this view, head direction consistency is a by-product of non-linguistic constraints on hierarchically organized temporal sequences. In particular, if recursively consistent combinations of grammatical regularities, such as those found in head-first and head-last languages, are easier to learn (and process) than recursively inconsistent combinations, then it seems plausible that recursively inconsistent languages would simply "die out" (or not come into existence), whereas the recursively consistent languages should proliferate. As a consequence languages incorporating a high degree of recursive inconsistency should be far less frequent among the languages of the world than their more consistent counterparts.
This talk will present converging evidence from four lines of research in support for this alternative explanation of word order universals. This evidence is derived from a theoretical analysis of rule interactions, from connectionist simulations (Christiansen & Devlin, 1997), from typological language data, and from artificial grammar learning in normal adults and aphasic patients. Together, this evidence suggests that constraints on the emergence of word order universals derive from non-linguistic constraints on the learning and processing of complex sequential structure. Thus, rather than a biological adaptation of learning mechanisms to fit linguistic structure, the evidence points to the adaptation of linguistic structure to fit pre-existing sequential learning mechanisms.
Christiansen, M.H. & Devlin, J.T. (1997). Recursive inconsistencies
are hard to learn: A connectionist perspective on universal word order
correlations. In Proceedings of the 19th Annual Cognitive Science
Society Conference (pp. 113-118). Mahwah, NJ: Lawrence Erlbaum
Associates.
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