The predictions of two contrasting approaches to the acquisition of transitive relative clauses were tested within the same groups of German-speaking participants aged from 3 to 5 years old. The input frequency approach predicts that object relative clauses with inanimate heads (e.g., the pullover that the man is scratching) are comprehended earlier and more accurately than those with an animate head (e.g., the man that the boy is scratching). In contrast, the structural intervention approach predicts that object relative clauses with two full NP arguments mismatching in number (e.g., the man that the boys are scratching) are comprehended earlier and more accurately than those with number-matching NPs (e.g., the man that the boy is scratching). These approaches were tested in two steps. First, we ran a corpus analysis to ensure that object relative clauses with number-mismatching NPs are not more frequent than object relative clauses with number-matching NPs in child directed speech. Next, the comprehension of these structures was tested experimentally in 3-, 4-, and 5-year-olds respectively by means of a color naming task. By comparing the predictions of the two approaches within the same participant groups, we were able to uncover that the effects predicted by the input frequency and by the structural intervention approaches co-exist and that they both influence the performance of children on transitive relative clauses, but in a manner that is modulated by age. These results reveal a sensitivity to animacy mismatch already being demonstrated by 3-year-olds and show that animacy is initially deployed more reliably than number to interpret relative clauses correctly. In all age groups, the animacy mismatch appears to explain the performance of children, thus, showing that the comprehension of frequent object relative clauses is enhanced compared to the other conditions. Starting with 4-year-olds but especially in 5-year-olds, the number mismatch supported comprehension-a facilitation that is unlikely to be driven by input frequency. Once children fine-tune their sensitivity to verb agreement information around the age of four, they are also able to deploy number marking to overcome the intervention effects. This study highlights the importance of testing experimentally contrasting theoretical approaches in order to characterize the multifaceted, developmental nature of language acquisition.

Previous studies have found that Hebrew-speaking children accurately comprehend object relatives (OR) with an embedded non-referential arbitrary subject pronoun (ASP). The facilitation of ORs with embedded pronouns is expected both from a discourse-pragmatics perspective and within a syntax-based locality approach. However, the specific effect of ASP might also be driven by a mismatch in grammatical features between the head noun and the pronoun, or by its relatively undemanding referential properties. We tested these possibilities by comparing ORs whose embedded subject is either ASP, a referential pronoun, or a lexical noun phrase. In all conditions, grammatical features were controlled. In a referent-identification task, the matching features made ORs with embedded pronouns difficult for five-year-olds. Accuracy was particularly low when the embedded pronoun was referential. These results indicate that embedded pronouns do not facilitate ORs across the board, and that the referential properties of pronouns affect OR processing.

Children's poor performance on object relative clauses has been explained in terms of intervention locality. This approach predicts that object relatives with a full DP head and an embedded pronominal subject are easier than object relatives in which both the head noun and the embedded subject are full DPs. This prediction is shared by other accounts formulated to explain processing mechanisms. We conducted a visual-world study designed to test the off-line comprehension and on-line processing of object relatives in German-speaking 5-year-olds. Children were tested on three types of object relatives, all having a full DP head noun and differing with respect to the type of nominal phrase that appeared in the embedded subject position: another full DP, a 1st- or a 3rd-person pronoun. Grammatical skills and memory capacity were also assessed in order to see whether and how they affect children's performance. Most accurately processed were object relatives with 1st-person pronoun, independently of children's language and memory skills. Performance on object relatives with two full DPs was overall more accurate than on object relatives with 3rd-person pronoun. In the former condition, children with stronger grammatical skills accurately processed the structure and their memory abilities determined how fast they were; in the latter condition, children only processed accurately the structure if they were strong both in their grammatical skills and in their memory capacity. The results are discussed in the light of accounts that predict different pronoun effects like the ones we find, which depend on the referential properties of the pronouns. We then discuss which role language and memory abilities might have in processing object relatives with various embedded nominal phrases.

Speakers’ referential choices differ in the degree of explicitness, ranging from very explicit expressions (such as lexical NPs, e.g., the boy) to less explicit expressions (such as pronouns, e.g., he, and null elements). We examine the referential choices of children with Specific Language Impairment (SLI), in order to differentiate between the linguistic and pragmatic abilities involved in the selection of appropriate referring expressions. Existing findings on referential choices by children with SLI are currently inconsistent and have mainly been reported based on narratives. We used an elicited production task to manipulate the referent’s accessibility by means of two factors: (a) contexts that instantiate different levels of contrast (one vs. two contrasts) and (b) the grammatical role of the expression (subject vs. object). We show that children with SLI and typically developing controls produce more explicit expressions for increased contrast levels and for objects than for subjects. Although children with SLI modify the explicitness of their referring expressions according to the accessibility of referents as typically developing children do, we also find varying production rates between the groups. We discuss how these differences in production rates surface as a consequence of language impairment, although the explicitness of referential choices remains otherwise largely unaffected.