Introduction

In Chapter 118 of this volume the original version of PT has been summarised. The reader will recall that PT is based on the notion of transfer of grammatical information which is modelled using feature unification, yielding different degrees of linguistic linearity. Most chapters of this volume utilised this approach and applied it to typologically different languages and different contexts of acquisition, thus demonstrating the typological plausibility of PT.

To highlight the nature of the proposed extension it may be useful to recall that the architecture of Lexical Functional Grammar (LFG) is based on three independently motivated parallel structures that have to be mapped onto each other. This is illustrated in Figure 1, which shows the predicator ―see‖ and its associated argument roles (―experiencer‖ and ―theme‖) as an example of an a(rgument)-structure19 and a rough sketch of the f-structure that this a-structure, as well as the corresponding c-structure, has to be mapped onto. The arrows in Figure 1 indicate the two kinds of mapping processes mentioned above.

see < experiencer theme >

PRED MODE .... SUBJ [ 'Peter' ] OBJ [ 'a dog' ] S NPsubj VP N V NPobj det N

Peter sees a dog PERSON = 3 PERSON = 3

NUM = SG NUM = SG a-structure

f-structure

c-structure

Figure 1: Three parallel structures in LFG

18

This referes to Chapter 1 of Pienemann (ed.) (2005) where this paper is published as Chapter 7.

19

In LFG a-structure represents information about the arguments selected by a predicate. F-structure represents grammatical information that is invariant across languages. In contrast, constituent structure is language-specific.

As mentioned above, the original version of PT focused on c-structure and the transfer of grammatical information within it, using feature unification. The modelling of feature unification, as envisaged in this approach, is illustrated in the example sentence shown in Figure 1 (i.e. ―Peter sees a dog‖). In this sentence the insertion of the verbal affix –s relies on information contained in the subject-noun phrase, namely the features PERS(ON) and NUM(BER) and their values PERS=3 and NUM=SG. These features are unified in S, as shown in Figure 2. In other words, the need to store grammatical information on PERS and NUM during sentence generation illustrates the non-linearity of this morphological process.

S

NPsubj VP

N V NPobj

det N

Peter sees a dog P ERSON = 3 P ERSON = 3

NUM = SG NUM = SG

Figure 2: Feature unification in the S-procedure

In the design of PT, the point of unification is related to a hierarchy of processability that reflects the time course of real time processing, as detailed in Levelt (1989). In this way a range of morphological and syntactic processes can be aligned with a universal hierarchy of processability, yielding developmental trajectories for the given target languages, as shown in several chapters of this volume.

The basic point of this chapter is to show that there are other aspects of language generation beyond the transfer of grammatical information within c-structure that generate linguistic non-linearity, and that these aspects of linguistic non-linearity may be able to be mapped onto the processability hierarchy. In particular, we will show that linguistic non-linearity can be created in the mapping of (i) a-structure onto f-structure and (ii) the mapping of c-structure onto f-structure. Both these components are based on

recent innovations in the architecture of LFG, and their inclusion in PT will yield a wider range of phenomena.

Given the psycholinguistic focus of this chapter, it is essential to bear in mind that one cannot assume the relationship between a-structure, f-stucture and c-structure to be linear. If these relationships were linear there would be no leeway for surface structure variation. In other words, semantic predicate-argument relationships could only be expressed by fixed surface word and phrase configurations. We know, however, that sentences may vary between active and passive, between affirmative and question forms, and that speakers may choose to place constituents in prominent positions by topicalising them or they may choose not to do so. Levelt (1989) demonstrates that in discourse, speakers use various linguistic devices to guide the listener‘s attention, including topicalisation and passivisation. Many of the structural choices that exist for the native speaker constitute devices of attention-direction and the representation of meaning in the hearer. In other words, attention-direction devices are necessitated by the nature of the comprehension process. These choices come, however, at a cost in terms of processing, since they require changes to the relationship between either a-structure and f-structure or beween c-structure and f-structure. Changes in these relationships will lead to linguistic non-linearity.

In Chapter 1 the phenomenon of non-linearity was discussed in the context of feature unification. This process is illustrated in Figures 1 and 2, which show that English SV- agreement marking involves a degree of non-linearity by virtue of two sets of lexical features being unified across constituent boundaries.

In the mapping of c-structure onto f-structure, non-linearity is created by the addition of adjuncts to canonical structure, and the assignment of discourse functions (FOC and TOP) to elements in c-structure that do not adhere to the canonical pattern. For instance, a canonical (i.e. one-to-one) relationship between c-structure and f-structure can be found in (1) where the first NP is the grammatical subject. In contrast, in (2) this relationship has to be modified.

(1) He likes Anne. (2) Anne, he likes.

The inclusion of this ‗dimension‘ of non-linearity has become possible because of the revised architecture of LFG. Bresnan and Mchombo (1987) and Bresnan (2001) show that some discourse roles (particularly TOPIC and FOCUS) are syntacticised and should therefore be represented in f-stucture. They demonstrate that these functions are subject to syntactic constraints in such cases as English interrogative clauses, cleft constructions, relative clauses, etc. These functions have c-structure properties that express their prominence in discourse. In particular, they often precede or c-command other constituents in the clause. The inclusion of the corresponding discourse roles in LFG yields a new dimension of accounting for developing states of interlanguage grammars that allow us to overcome some of the limitations of PT, particularly Kempen‘s (1998) concern about the absence of the S-procedure in early interlanguage development.

Non-linearity is even more subtle in the mapping of non-canonical argument structure onto f-structure. It is caused by ‗exceptional lexical entries‘ with intrinsic non-canonical a-structure (e.g. ―receive‖, ―please‖) and by non-default verb forms (e.g. passives and causative constructions). In both cases, semantic roles are mapped onto non-default grammatical functions. For intance, in the sentence ―the result pleased him‖ the experiencer is mapped onto the grammatical object, and the theme is mapped onto the subject. These mapping processes go against the default the learner creates earlier and thus add to the non-linearity of the overall production process. Again, this dimension of non-linearity in developing interlanguage grammars can be represented only because in the revised version of LFG the correspondence between argument struture and functional structure is modelled by a formal theory, Lexical Mapping Theory (LMT), which has been incorporated into the LFG formalism.

Apart from our objective of extending the scope of PT by capturing systematically the correspondence between the three parallel levels of representation in a dynamic learner system, there is an additional reason for extending PT, namely to overcome limitations of the original theory.

Some of the limitations of PT were discussed and amended in Chapter 2. One additional limitation was raised by Kempen (1998) who pointed out that in PT, sentences were assumed to be assembled at a point in development before the S-procedure had developed that is needed for the assembly of sentences. Pienemann (1998b) responded that PT was based on the assumption that before the development of the S-procedure, learners produce sentences on the basis of a direct correspondence between argument

structure and surface grammatical form. Such direct correspondences (or ‗direct mapping‘) do indeed constitute an alternative and processable route that has been assumed to be accessible to beginning language learners by a number of scholars (e.g. Bever, 1970; Slobin, 1985; Pinker, 1984, 1989). The mere assumption of direct mapping processes does not, however, spell out any formal detail of these processes in the context of an overall theory, nor does it formally interface with the architecture of the proposed theory of language development. It is the objective of this chapter to develop such a formal account of the mapping processes required before the development of the S-procedure and to formally interface this with PT and the overall architecture of LFG.

This chapter is structured as follows. In Section 2 we will highlight the role of LFG as a grammatical formalism in the psycholinguistic framework of Processability Theory. This step is crucial because one needs to bear in mind that even though the objectives of LFG and PT overlap they are not identical. Whereas LFG is a theory of grammar, PT is designed to model the developmental dynamics of interlanguage systems on the basis of the architecture of the syntactic encoding system. In Section 3 we will sketch out two sets of correspondence principles entailed in LFG, in order to be in a position to develop our fundamental line of argument. In Section 4 those correspondence principles will be integrated into PT, generating a set of novel predictions for interlanguage development.