Language disorders as a window on universal grammar: an abstract theory of agreement for IP, DP, and V-PP.

A new concept of Agreement (AGR) has been represented as a Formal Feature that can appear in a wide range of different configurations (Chomsky, 1998). A case study from language disorders supports and extends this abstract concept. The child shows no agreement in Inflectional Phrase me can and Determiner Phrase them eyes. We then extend the notion of AGR to include verb-Prepositional Phrase relations, where the child also systematically avoids certain prepositions (go beach). The analysis is supported by intuitional data from compounds (sweep with broom --> broom-swept). We also define a systematic notion of Possible deficit as a premature fixation of functional items which normally require additional Phi-features. The notion of Maximization of Formal Features then emerges as a significant feature of learnability from both a normal and disordered perspective.