Reconsidering Kirby’s compositionality model toward modelling grammaticalisation

Grammaticalisation is a potent candidate to structuralise and complexify human languages in the evolution of language. It is a phenomenon of language change, in which content words such as nouns and verbs change into functional words such as auxiliaries and prepositions. New functional categories, tense, mood, and so forth, can emerge in a language structure through grammaticalisation, then structure and lexicon of a language can become complex and fruitful. It is important to understand the process of and the cognitive ability for grammaticalisation in the context of the origin and the evolution of language. We discuss constructing a computational model for grammaticalisation to achieve this end. It is assumed that reanalysis and analogy are underlying mechanisms of grammaticalisation (Hopper & Traugott, 2003). Reanalysis is structural change without observable change in forms. This occurs when a hearer understands a form to have a structure differently from that of a speaker. Analogy is to apply a grammatical rule to forms in which the rule was not applied formerly. These mechanisms postulate a coginitive ability to find analogy among situations and among forms. W