Representation, information theory and basic word order.

Abstract

Many of the world's languages display a preferred ordering of subject, object and verb, known as that language's basic word order. There are six logically possible basic word orders, and while each occurs in at least one known language, not all are found equally frequently. Some are extremely rare, while others are used by almost half the world's languages. This highly non-uniform cross-linguistic distribution of basic orders is a fundamental explanatory target for linguistics. This thesis tackles this problem from a psychological perspective. It constitutes an advance over previously proposed explanations in that it is compatible not only with the distributions observed today, but with what is known of broad trends in the word order change which happen over hundreds of years. There are two largely independent components of the explanation given in this thesis, which is necessary to be compatible with both synchronic and diachronic evidence. The first component is focused on the structures which the human mind uses to represent the meanings of sentences. While mental representations of meaning are not inherently serial (hence ordered) like spoken language, we can think of the different components in these representations as being ordered in a different sense, based on some components being more accessible to cognitive processing than others. This thesis develops the idea that the word order used most often in the earliest human languages, which are taken to rely on a direct interface between mental representations and motor control systems, were determined by a "word order of the language of thought". The second component is focused on the functional adequacy of different word orders for high speed, reliable communication. The driving idea here is that human language represents a rational solution to the problem of communication. The mathematical formalism of information theory is used to determine the gold standard for solutions to this problem, and this is used to derive a ranking of word orders by functionality. This thesis develops a novel perspective on word order functionality in which cross-linguistic preferences are ultimately a reflection of statistical properties of the events which languages describe.