Merced Proceedings of the Annual Meeting of the Cognitive Science Society Title Simulating the temporal reference of Dutch and English Root

Hoekstra & Hyams (1998) claim that the overwhelming majority of Dutch children’s Root Infinitives (RIs) are used to refer to modal (not realised) events, whereas in English speaking children, the temporal reference of RIs is free. Hoekstra & Hyams attribute this difference to qualitative differences in how temporal reference is carried by the Dutch infinitive and the English bare form. Ingram & Thompson (1996) advocate an input-driven account of this difference and suggest that the modal reading of German (and Dutch) RIs is caused by the fact that infinitive forms are predominantly used in modal contexts. This paper investigates whether an input-driven account can explain the differential reading of RIs in Dutch and English. To this end, corpora of English and Dutch Child Directed Speech were fed through MOSAIC, a computational model that has already been used to simulate the basic Optional Infinitive phenomenon. Infinitive forms in the input were tagged for modal or non-modal reference based on the sentential context in which they appeared. The output of the model was compared to the results of corpus studies and recent experimental data which call into question the strict distinction between Dutch and English advocated by Hoekstra & Hyams. Root Infinitives in Child Language A striking feature of the speech of children who are acquiring their native language, is that, in many languages, children go through a stage where they produce Root Infinitives (non-finite verb forms in contexts that require a finite verb form). Thus, English-speaking children may produce utterances such as (1), and Dutch children may produce utterances such as (2). (1) Daddy drink coffee (2) Papa koffie drinken (Daddy coffee drink-inf) This phenomenon has been subject to considerable linguistic theorizing, as the fact that it occurs in several languages (including English, Dutch, Swedish, German and French) suggests the operation of invariant principles. A particularly influential Nativist theory has been provided by Wexler (1994). According to Wexler’s Optional Infinitive (OI) Hypothesis, by the time children begin to produce multiword speech, they have already correctly set all the basic inflectional and clause structure parameters of their language. They thus have adult-like knowledge of the word order and inflectional properties of the language they are learning. However, there is a stage of development (the Optional Infinitive stage), during which the abstract features of Tense (TNS) and Agreement (AGR) can be absent from the underlying representation of the sentence. This results in children initially using both finite and non-finite verb forms in contexts in which a finite form would be obligatory in the adult language. The great strength of the Optional Infinitive Hypothesis is that it explains the data from a wide variety of languages, as well as the relative sparseness of other errors. However, the theory also has some important weaknesses. Firstly, the theory assumes a large amount of innate knowledge and ignores the possibility that the Optional Infinitive phenomenon may be understood as the result of an input-driven learning process without the need to assume large amounts of innate knowledge. Simulations with the MOSAIC model have already shown that a simple learning mechanism which is sensitive to the distributional characteristics of the input can give a close quantitative fit to the prevalence of the Root Infinitives in English and Dutch over a range of MLUs (Freudenthal, Pine & Gobet (2002a, 2003, in preparation). Secondly, while the Optional Infinitive phenomenon occurs in several languages, cross-linguistic differences exist in the finer detail of the phenomenon that are problematic for Wexler’s theory. One obvious way of explaining these differences is in terms of differences in the distributional characteristics of the language being learned. In this paper we assess the viability of such an explanation by simulating cross-linguistic differences in the fine detail of the OI-phenomenon in Dutch and English using MOSAIC. The central aim of this paper is therefore to investigate whether the same mechanism that captures one of the key similarities in the speech of children learning different languages can also capture differences in the way