The development of the copula in Child English

The dissertation summarized here provides an account of the fact that young children acquiring English (around age 2) often produce utterances like (1), in which they omit a form of the copula, be.

(1)I in the kitchen.

Children’s production of forms like (1) is interesting for two main reasons: firstly, utterances like these do not occur in the input (adult English); secondly, children’s omission of the copula conforms to a systematic pattern (it is neither across the board, nor haphazard). In particular, children omit the copula far less frequently in utterances like (2).

(2)He’s a dog.

The difference between the constructions in (1) and (2) can be characterized in terms of the well-known semantic stage-level/individual-level contrast. That is, a location such as ‘in the kitchen’ denotes a stage-level property of the subject; a predicate such as ‘a dog’ denotes an individual-level property of the subject. I argue for a syntactic difference between stage- and individual-level predicates: stage-level predicates contain additional functional structure (AspP) that individual-level predicates lack. Cross-linguistic support for this proposal is provided.

As for why children acquiring English omit the copula in main clauses, I link this to the fact that non-finite main clauses are permitted in child English. I define finiteness in terms of a binding relation between an abstract Tense Operator (T_OP) (located in CP) and Infl. In certain grammars (among them child English) T_OP may bind Asp instead of Infl, if Asp is projected in the particular clause. However, this binding relation does not result in the clause being finite. Since Asp is projected in clauses with stage-level predicates, but not in those with individual-level predicates, it follows that stage-level predicates may occur in non-finite clauses while individual-level predicates occur with a finite clause. Coupled with the hypothesis that an overt copula is finite (in the sample studied here it is inflected over 99% of the time) and an omitted copula indicates non-finiteness, the pattern of copula omission and production in child English is accounted for.