Simulating the cross-linguistic development of optional infinitive errors in MOSAIC.

Simulating the Cross-Linguistic Development of Optional Infinitive Errors in MOSAIC Daniel Freudenthal (D.Freudenthal@liv.ac.uk) Julian Pine (Julian.Pine@liv.ac.uk) School of Psychology, University of Liverpool L69 7ZA Liverpool, UK Fernand Gobet (Fernand.Gobet@Brunel.ac.uk) School of Social Sciences and Law, Brunel University Uxbridge, Middlesex, UB8 3PH, UK Bloom, 1990; Pinker, 1984; Valian, 1991). More recently, however, it has been argued that they reflect the child’s optional use of (root) infinitives (e.g. go) in contexts where a finite form (e.g. went, goes) is obligatory in the adult language (Wexler, 1994, 1998). This interpretation reflects the fact that children produce (root) infinitives not only in English, where the infinitive is a zero-marked form, but also in languages such as Dutch (Wijnen et al. 2001) and German, where the infinitive carries its own infinitival marker (-en). For instance, children learning Dutch may produce utterances such as: Abstract The Optional Infinitive (OI) phenomenon in children’s speech has attracted a great deal of attention due to its occurrence in a variety of languages (including English, Dutch and German), and its apparent absence in other languages (such as Spanish and Italian). Wexler (1998) explains this pattern of results in terms of a Unique Checking Constraint that interacts with cross-linguistic differences in the underlying grammar to result in Optional Infinitive errors in obligatory subject languages (which require double-checking), but not in pro-drop languages (which do not require double-checking). While Wexler’s account explains the cross-linguistic data, it attributes a great deal of innate linguistic knowledge to the child, and ignores the possibility that the cross-linguistic data may be equally well explained by the interaction between a simple distributional learning mechanism and the surface characteristics of the language. This paper presents simulations of the Optional Infinitive phenomenon across 4 languages (English, Dutch, German, and Spanish) using MOSAIC, a simple distributional analyser with no built-in syntactic knowledge. MOSAIC clearly simulates the different rates of Optional Infinitive errors across the languages, suggesting (a) that it is possible to explain the basic OI phenomenon without assuming large amounts of innate linguistic knowledge, and (b) that cross-linguistic differences in the OI phenomenon may be related to differences in the surface characteristics of the languages being learned. (3a) Pappa eten* (4a) Mamma drinken* (Daddy (to) eat) (Mummy (to) drink) Instead of (3b) Pappa eet (4b) Mamma drinkt (Daddy eats) (Mummy drinks) According to Wexler (1998), the Optional Infinitive phenomenon can be explained as follows. By the time children begin to produce multi-word utterances, they have already set all the basic inflectional and clause structure parameters of their language. However, their grammars are governed by a Unique Checking Constraint that is ‘genetically specified (and withering away in time)’ (Wexler, 1998: 27). The Unique Checking Constraint may prevent the child from checking the D-feature of the subject DP against more than one D-feature (in this case the D-features of Tense and Agreement). As a result, Tense and Agreement can be optionally under-specified in the underlying representation of the sentence, and the child may produce non-finite verb forms (forms that are not marked for tense or agreement) in contexts in which a finite verb form is required. The main strength of Wexler’s account is that it can explain data from a range of different languages. Thus, it can explain why children produce Optional Infinitive errors at high rates in obligatory subject languages like English, Dutch and German, which require the child to check against two D- features: Tense and Agreement. However, it can also explain why children make few Optional Infinitive errors in INFL- licensed null subject languages like Spanish and Italian, Introduction Between two and three years of age, children learning English often produce utterances that appear to lack inflections, such as past tense markers or third person singular agreement markers. For example, children may produce utterances as: (1a) That go there* (2a) He walk home* instead of (1b) That goes there (2b) He walks home Traditionally, such utterances have been interpreted in terms of absence of the appropriate knowledge of inflections (Brown, 1973) or the dropping of inflections as a result of performance limitations in production (L. Bloom, 1970; P.