Productivity and Reuse in Language A dissertation presented by

A much–celebrated aspect of language is the way in which it allows us to make “infinite use of finite means ” (von Humboldt, 1836). This property is made possible because language is fundamentally a productive computational system: Novel expressions can be composed from a large inventory of stored, reusable parts. For any given language, however, there are many more potential ways of forming novel expressions than can actually be used in practice. For example, English contains suffixes that are highly productive (e.g.,-ness; Lady-Gagaesqueness, pine-scentedness), but also contains suffixes which can only be reused in specific, existing words (e.g.,-th; truth, width, warmth). How are such differences in productivity and reusability represented? How can the child acquire this system of knowledge? This thesis presents a formal model of productivity and reuse which treats the problem as a structure–by–structure inference in a Bayesian framework. The model—Fragment Grammars, a generalization of Adaptor Grammars (Johnson et al., 2007a)—is built around two proposals. The first is that anything that can be computed can be stored. The specific computational mechanism b