Correlation with Null Objects?

There is a wide consensus in the literature on language acquisition that functional elements are acquired late, although there is crosslinguistic variation with respect to those elements that are produced later and to the rates of omission for different languages (see Radford 1994, Guasti 2002 for relevant data and for a review of the literature). Since pronominal clitics are elements whose syntax is dependent on the functional structure of the clause, it is expected that clitics are potential candidates for late acquisition. In this paper, we present a summary of recent discoveries on the acquisition of clitics, showing that clitics may be omitted or not depending on the language being acquired. Afterwards, we present the summary of the results of an experiment run with European Portuguese children in which accusative 3 person clitics were elicited (Costa & Lobo 2006). The European Portuguese data show that, for this language, there is no positive correlation between clitic omission and the availability of past participle agreement in the adult language, contrary to the predictions made in Wexler et al. (2003). Bearing these results in mind, the aim of the paper is to compare two hypotheses that intend to explain the pattern of omission found in European Portuguese: feature checking vs. postsyntactic complexity. For a comparative evaluation of these two hypotheses, it becomes relevant to study the behaviour of children with non-accusative and with reflexive clitics. The goal of the paper is to present the results of two experiments: one eliciting reflexive clitics, and another experiment eliciting 1, 2 and 3 person dative clitics. It will be shown that the different omission rates found allow for comparing the two hypotheses under evaluation, and favour the hypothesis in terms of post-syntactic complexity.