Accounting for development: Structure-building hypothesis

Following the assumption of a gradual development of syntax (Structure-building or Weak Continuity hypothesis), we assume that the acquisition of the target word order of a given language is determined by the interaction of innate principles (e.g. X-bar theory) and input data (see, for example, Plaza-Pust 2000, Vainikka & Young-Scholten 1996 for adult second language acquisition, Siebert-Ott 2001 for child second language acquisition, and Fritzenschaft et al. 1991, Gawlitzek-Mai- wald et al. 1992 for child first language acquisition).

The minimal structural domains learners start out with are projections of lexical categories (Radford 1990: 43f.). These minimal structures already instantiate the basic X-bar template, as illustrated in example (4) (Radford 1990: 95). They are categorial-thematic in that all constituents belong to the inventory of lexical categories and all sister constituents are in a thematic relationship to the head.

Notice that grammatical principles are not violated in the early prefunctional grammar. Rather, processes like case-checking simply operate vacuously because the necessary grammatical categories and their associated features are not yet in place. Following Hohenberger (2002: 98f.) FCs emerge after the lexicon and the learner’s phrase marker have reached a critical size. Learners are then faced with the task of specifying the target-language features of these categories.