Syntax, Acquisition of

Probably there are very few fields in cognitive science that have shown as distinct a growth in the last decade as the field of SYNTAX acquisition. The increase in preciseness and knowledge has been extremely large, so large as to make the field hardly recognizable when compared to work of much more than a decade ago. In this short piece, I can hardly do more than to mention a few of the very active areas of research and some of the major results.

1. Inflectional and Clausal Development At one time, it was thought by almost every approach to syntax acquisition (e.g., Wanner and Gleitman 1982) that a major reason that children's utterances (e.g., me no going) seemed to be different from adults' utterances (e.g., I am not going) is that children did not know the (morphonological and/or morphosyntactic) properties of inflectional elements (e.g., English third singular -s), the case of pronouns, the existence of auxiliary verbs, and so on. It looked as if inflectional elements were omitted or that their properties were incorrectly known to the child. On the basis of extensive empirical research, the field has completely thrown over this idea, however. The main tool for this demonstration has been the correlation between word order and MORPHOLOGY in the optional infinitive stage of development (Wexler 1993; roughly up to 3;0, depending on the language). As Wexler showed, children in many languages often use nonfinite main verbs alongside finite main verbs, but they know the morphosyntactic and morphological properties of finiteness. One of the first examples was provided by Pierce (1992) concerning French. Finite and nonfinite verbs in French occur in different distributional positions -- for example, French finite verbs precede negation pas and nonfinite verbs follow pas. Pierce determined the finiteness of the verb by morphological form and the word order by observing where the verb appeared with respect to pas. The following table from Wexler 1993, based in Pierce's data, shows the number of utterances with the relevant properties, from children around 2;0. Columns represent verb morphology, rows represent order of the verb and pas.

+finite - finite

pas verb 11 77

verb pas 185 2

The stunning result is that despite the fact that children at this early age use very many nonfinite utterances (ungrammatical in matrix position) as well as finite utterances, they get the word-order facts correct. Even more stunning is the fact that, as Wexler (1993) showed, the correlation between morphology and word order holds over many different languages, despite very different constructions. Thus, Poeppel and Wexler (1993) showed that German children used nonfinite root verbs as well as finite ones, but they almost always placed the finite verbs in second position (correct for this V2 language) and the nonfinite ones in final position, again correct for German, an SOV language.

Wexler (1993) called the stage at which these root nonfinite forms occur the optional infinitive (OI) stage and showed that it occurred in many different languages. From the properties of the OI stage, it can be deduced that children at an extremely young age have learned the central parameter values of the clausal/inflectional syntax of their language. For example, the French children discussed above have learned that the finite verb raises around negation (to an inflectional position) whereas English-speaking children do not raise the verb (correct for their language). The German results show that German children know that German is a V2 language (there are many other related phenomena) and that German is an SOV language. Wexler (1996) hypothesized that Very Early Parameter Setting (VEPS) was true: namely, children have set the central clausal/inflectional parameters of their language correctly at an extremely early age, before 2;0, perhaps before they have entered the multiword utterance stage at about 1;6. Evidence to date suggests that VEPS is true.

Thus the learning of language-particular aspects of grammar (parameters) is extremely fast and might be mostly done (for central parameters) before children start speaking in more than single-word utterances. Thus crucial grammatical learning is a kind of perceptual learning, done without any kind of overt error made by the child, that can be corrected by an adult. At the moment, it can't be determined exactly how early children set parameters correctly because of a limitation of experimental method: the key instrument has been naturalistic production, and the data are extremely sparse before 1;6. The development of infant techniques in this field will be necessary to probe earlier.

Not only are the parameters set correctly (the morphosyntactic part), but for the most part, the morphophonological aspects of inflection are known. Thus Poeppel and Wexler (1993) showed that extremely young German children didn't make mistakes on (subject-verb) agreement: either a nonfinite verb was used or a correctly agreeing one. A further example is that children almost never use a third-singular verb in English with a first-person pronoun (*I likes candy); there are almost no examples out of hundreds of possibilities (Harris and Wexler 1996). Children know that -s means third-person singular from an extremely early age. This contradicts earlier suggestions (Clahsen and Penke 1992) that children have a difficult time with agreement. The reason that this appeared to be so was that it wasn't understood that many of the child's forms are nonfinite forms.

One central mystery remains, alongside the discovery that children at the earliest observed ages know both the universal and language-particular aspects of clause structure, inflection, functional categories, and verb movement. This is the question of why they use optional infinitives at all. In his original paper, Wexler (1993) suggested that children had certain difficulties with tense. Other proposals have been made by Rizzi (1994), Hoekstra and Hyams (1995), Wexler (1996, 1997), and Schütze and Wexler (1996), among others. There is an intense debate as to the best model to explain the OI stage, a debate being carried out with a detail of syntactic and quantitative analysis of children's abilities that is truly astonishing compared to what was known only a decade ago. The rigorous theoretical analysis and detailed quantitative empirical study of early syntax has certainly pushed the field to a new level.

It is the foregoing work that has been primarily responsible for the fall from favor of the proposal by Radford (1990) that children do not have functional categories, for there is no reasonable way to account for the correlation between morphology and word order if children do not have functional categories. For balance, let me point out that at least Atkinson (1996) remains not completely convinced. I should also point out that there is now at least a beginning array of experimental results on comprehension confirming the general outlines of the OI stage (Schonenberger et al. 1995; Rice, Wexler, and Redmond 1998).

2. Null Subjects An important early major result about the development of inflection within the principles-and-parameters approach was Hyams' (1986) discovery that English-speaking children very often use null subjects (e.g., baking cookies), despite the fact that English is not a null-subject language (unlike Italian, in which subjects are typically omitted from the sentence). Hyams suggested that these children had "mis-set" the null-subject parameter, so that English- speaking children thought that null subjects were grammatical, as in Italian. Since Hyams's work, it has been discovered that in every language that has been studied at early ages in this regard, children use null subjects.

Occasionally it has been suggested that the null subjects are the result of some kind of memory deficit (Bloom 1990) or production constraint (Gerken 1991). However, the empirical evidence is not consistent with this idea (Hyams and Wexler 1993; Bromberg and Wexler 1995). The weight of this evidence suggests that indeed children at an early age consider some null subjects to be grammatical even when their language isn't a null-subject language.

Thus one major part of Hyams's proposal is still considered to be correct -- namely, that null subjects are grammatical for children. However, a second major part of Hyams's proposal does not now seem to be correct (as Hyams herself agrees: e.g., Sano and Hyams 1994). Namely, it does not appear that children have mis-set the null-subject parameter. Rather, null subjects appear to be the product of the OI stage. Children know that English, for example, is not null-subject in the Italian sense, but they produce null subjects because certain clauses (those missing tense, according to the hypothesis of Schütze and Wexler 1996) allow a null subject. Probably the strongest evidence for this position is the result of Roeper and Rohrbacher 1995 and Bromberg and Wexler 1995 that in wh-questions, children use null subjects only when the sentence is an OI, when tense is missing (e.g., where going, but not *where is going). If English were truly an Italian-style null-subject language, null subjects would be grammatical even with a tensed verb. (Any suggestion that subjects are dropped because the first part of the sentence is "difficult," e.g., Bloom 1990, can't hold for the large numbers of wh-questions with null subjects, because the wh-form is at the beginning of the sentence.)

Italian children, on the other hand, will allow wh- questions with null subjects, because Italian is an Italian-style null-subject language. Thus the null-subject parameter is consistent with Wexler's (1996) VEPS: children have even set the null-subject parameter correctly at the earliest observed age.

Greatly simplifying the myriad structures studied, I have tried only to give enough detail to suggest the theoretical and empirical richness of this part of the field at the current moment and to suggest how this richness of detail represents something quite new in the study of linguistic development. There are an extremely large number of interrelated crosslinguistic and cross-construction generalizations that must be accounted for by any theory of linguistic development, and any theory that does not account for at least a large subset of these phenomena can hardly lay claim to being a serious contender for consideration. It is primarily for this reason that theories that involve only very general mechanisms of learning, and no linguistic details, are not seriously considered by the field: they seem to be nonstarters from the standpoint of empirical coverage. The primary task facing these "general learning mechanism/statistical procedures" theories is to make even a small dent in the empirical coverage that the major theories can already account for.

3. Development of Chains and Maturation Is there any delay in knowledge of syntactic properties, or do the youngest children know everything about syntax? Borer and Wexler (1987; 1992) claimed that A-chains (argument-chains) are delayed in development, perhaps into the third or fourth year. A-chains involve movement of an argument to another A-position (argument-type position, not operator position). A primary example given by Borer and Wexler is the A-movement involved in the raising of an object into the subject position in the verbal passive construction (e.g., the fox was kicked by the lion, where the fox was raised from object position after kicked to subject position; see also GRAMMATICAL RELATIONS). Such passive constructions are known to be delayed in English-speaking children (2- and 3-year-old children do not correctly understand who kicked who in the fox was kicked by the lion). Borer and Wexler (1987) showed that adjectival passives (e.g., the toy is broken), which do not contain A-chains, were very early in English-speaking children, and they argued that the semantic and structural complexity of adjectival and verbal passives were about on a par. They thus suggested that it was the A-chain representation that was disallowed by children until a later age. Thus the children couldn't represent verbal passive constructions.

Furthermore, Borer and Wexler (1987) argued that the delay in A-chains was maturational; that A-chains were delayed because of biological development. Since then, the issue of maturation versus learning has been a hot topic of debate in LANGUAGE ACQUISITION. There are no other explanations of growth/change that have been suggested, except for learning and maturation. Borer and Wexler raised an objection to a learning analysis for a delayed construction like the passive, namely the Triggering Problem: If change occurs in grammar because of a reaction to an input trigger, why does this change often take years? A tip-off that maturation may in fact be on the right track can be found in the OI stage. Note that in that stage all the properties that we know must be learned -- namely, the ones that differ from language to language -- are learned extremely early (VEPS). It is the universal (apparently) property of finiteness of root clauses (morphology aside) that develops late. Thus a universal property is late, whereas an experience- dependent, learned property is early. This suggests maturation.

The topic of A-chains has recently been invigorated with a number of new constructions and languages studied (Babyonyshev et al. 1994, Snyder, Hyams, and Crisma 1995). One might expect that this topic will be a central one, as the development of complex syntax is investigated in the years to come.

References

Atkinson, M. (1996). Now, hang on a minute: Some reflections on emerging orthodoxies. In H. Clahsen, Ed., Generative Perspectives on Language Acquisition. Amsterdam: Benjamin, pp. 451-485.

Babyonyshev, M., R. Fein, J. Ganger, D. Pesetsky, K. Wexler, and S. Avrutin. (1994). Maturation of syntax: New evidence from the acquisition of unaccusatives in Russian. Paper presented at the Nineteenth Annual Boston University Conference on Language Development.

Babyonyshev, M., R. Fein, J. Ganger, D. Pesetsky, and K. Wexler. (1998). The maturation of grammatical principles: Evidence from Russian unaccusatives. Unpublished ms, MIT and Microsoft Corporation, pp. 1-63.

Bloom, P. (1990). Subjectless sentences in child language. Linguistic Inquiry 21(4):491-504.

Borer, H., and K. Wexler. (1987). The maturation of syntax. In T. Roeper and E. Williams, Eds., Parameter Setting, pp. 123-172.

Borer, H., and K. Wexler. (1992). Bi - unique relations and the maturation of grammatical principles. Natural Language and Linguistic Theory 10:147-189.

Bromberg, H., and K. Wexler. (1995). Null subjects in child wh - questions. MIT Working Papers in Linguistics 26:221-247.

Clahsen, H., and M. Penke. (1992). The acquisition of agreement morphology and its syntactic consequences. In J. Meisel, Ed., The Acquisition of Verb Placement. Dordrecht: Kluwer.

Gerken, L. (1991). The metrical basis for children's subjectless sentences. Journal of Memory and Language 30:431-451.

Harris, A., and K. Wexler. (1996). The optional - infinitive stage in child English. In H. Clahsen, Ed., Generative Perspectives on Language Acquisition. Amsterdam: Benjamin, pp. 1-42.

Hoekstra, T., and N. Hyams. (1995). The syntax and interpretation of dropped categories in child language: A unified account. Proceedings of the West Coast Conference on Formal Linguistics XIV. Stanford, CA: CSLI Publications.

Hyams, N. (1986). Language Acquisition and the Theory of Parameters. Dordrecht: Reidel.

Hyams, N., and K. Wexler. (1993). On the grammatical basis of null subjects in child language. Linguistic Theory 24(3):421-459.

Klima, E., and U. Bellugi. (1966). Syntactic regularities in the speech of children. In J. Lyons and R. Wales, Eds., Psycholinguistic Papers. Edinburgh: Edinburgh University Press, pp. 183-207.

Pierce, A. (1992). Language Aquisition and Syntactic Theory: A Comparative Analysis of French and English Child Language. Dordrecht: Kluwer.

Poeppel, D., and K. Wexler. (1993). The full competence hypothesis of clause structure in early German. Language 69:1-33.

Radford, A. (1990). Syntactic Theory and the Acquisition of English Syntax. Oxford: Blackwell.

Rice, M., K. Wexler, and S. M. Redmond. (1998). Comprehension of an extended infinitive grammar: Evidence from English-speaking children with specific language impairment. Paper presented at Twenty-second Annual Boston University Conference on Language Development.

Rizzi, L. (1994). Some notes on linguistic theory and language development: The case of root infinitives. Language Acquisition 3(4):371-393.

Roeper, T., and B. Rohrbacher. (1995). Null subjects in early child English and the theory of economy of projection. Unpublished ms, University of Massachusetts, Amherst, and the University of Pennsylvania.

Sano, T., and N. Hyams. (1994). Agreement, finiteness, and the development of null arguments. Proceedings of NELS 24:1-16.

Schonenberger, M., A. Pierce, K. Wexler, and F. Wijnen. (1995). Accounts of root infinitives and the interpretation of root infinitives. GenGenP 3(2):47-71.

Schütze, C., and K. Wexler. (1996). Subject case licensing and English root infinitives. BUCLD 20 Proceedings, pp. 670-681.

Snyder, W., N. Hyams, and P. Crisma. (1995). Romance auxiliary selection with reflexive clitics: Evidence for early knowledge of unaccusativity. Proceedings of the Twenty-sixth Annual Child Language Research Forum. Stanford, CA: Stanford Linguistics Association (SLA) and CSLI Publications, pp. 127-136.

Wexler, K. (1982). A principle theory for language acquisition. In E. Wanner and L. R. Gleitman, Eds., Language Acquisition: The State of the Art. Cambridge: Cambridge University Press, pp. 289-315.

Wexler, K. (1993). Optional infinitives, head movement, and the economy of derivations. In D. Lightfoot and N. Hornstein, Eds., Verb Movement. Cambridge: Cambridge University Press, pp. 305-350.

Wexler, K. (1996). The development of inflection in a biologically based theory of language acquisition. In M. L. Rice, Ed., Toward a Genetics of Language. Hillsdale, NJ: Erlbaum, pp. 113-144.

Wexler, K. (l997). D - Interpretability and interpretation in the OI stage. Presented at the Workshop on Interpretation of Root Infinitives and Bare Verbs, MIT, January 13,14.

Syntax, Acquisition of

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References

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