Publications

Abstract

In a paper entitled “Against markedness (and what to replace it with)”, Haspelmath argues “that the term ‘markedness’ is superfluous”, and that frequency asymmetries often explain structural (un)markedness asymmetries (Haspelmath 2006). We investigate whether this argument applies to Object and Verb orders in main (VO, marked) and subordinate (OV, unmarked) clauses of spoken and written German and Dutch, using English (without VO/OV alternation) as control. Frequency counts from six treebanks (three languages, two output modalities) do not support Haspelmath’s proposal. However, they reveal an unexpected phenomenon, most prominently in spoken Dutch and German: a small set of extremely high-frequent finite verbs with unspecific meanings populates main clauses much more densely than subordinate clauses. We suggest these verbs accelerate the start-up of grammatical encoding, thus facilitating sentence-initial output fluency

Abstract

Students who are learning to write in a foreign language, often want feedback on the grammatical quality of the sentences they produce. The usual NLP approach to this problem is based on parsing student-generated text. Here, we propose a generation-based ap- proach aiming at preventing errors ("scaffolding"). In our ICALL system, the student constructs sentences by composing syntactic trees out of lexically anchored "treelets" via a graphical drag & drop user interface. A natural-language generator computes all possible grammatically well-formed sentences entailed by the student-composed tree. It provides positive feedback if the student-composed tree belongs to the well-formed set, and negative feedback otherwise. If so requested by the student, it can substantiate the positive or negative feedback based on a comparison between the student-composed tree and its own trees (informative feedback on demand). In case of negative feedback, the system refuses to build the structure attempted by the student. Frequently occurring errors are handled in terms of "malrules." The system we describe is a prototype (implemented in JAVA and C++) which can be parameterized with respect to L1 and L2, the size of the lexicon, and the level of detail of the visually presented grammatical structures.

Abstract

We present an overview of several corpus studies we carried out into the frequencies of argument NP orderings in the midfield of subordinate and main clauses of German. Comparing the corpus frequencies with grammaticality ratings published by Keller’s (2000), we observe a “grammaticality–frequency gap”: Quite a few argument orderings with zero corpus frequency are nevertheless assigned medium–range grammaticality ratings. We propose an explanation in terms of a two-factor theory. First, we hypothesize that the grammatical induction component needs a sufficient number of exposures to a syntactic pattern to incorporate it into its repertoire of more or less stable rules of grammar. Moderately to highly frequent argument NP orderings are likely have attained this status, but not their zero-frequency counterparts. This is why the latter argument sequences cannot be produced by the grammatical encoder and are absent from the corpora. Secondly, we assumed that an extraneous (nonlinguistic) judgment process biases the ratings of moderately grammatical linear order patterns: Confronted with such structures, the informants produce their own “ideal delivery” variant of the to-be-rated target sentence and evaluate the similarity between the two versions. A high similarity score yielded by this judgment then exerts a positive bias on the grammaticality rating—a score that should not be mistaken for an authentic grammaticality rating. We conclude that, at least in the linearization domain studied here, the goal of gaining a clear view of the internal grammar of language users is best served by a combined strategy in which grammar rules are founded on structures that elicit moderate to high grammaticality ratings and attain at least moderate usage frequencies.

Abstract

This paper is an abridged version (in Dutch) of an in-press article by the same author (Kempen, G. (2008/9). Clausal coordination and coordinate ellipsis in a model of the speaker. To be published in: Linguistics). The two papers present a psycholinguistically inspired approach to the syntax of clause-level coordination and coordinate ellipsis. It departs from the assumption that coordinations are structurally similar to so-called appropriateness repairs Ñ an important type of self-repairs in spontaneous speech. Coordinate structures and appropriateness repairs can both be viewed as ÒupdateÓ con-structions. Updating is defined as a special sentence production mode that efficiently revises or augments existing sentential structure in response to modifications in the speakerÕs communicative intention. This perspective is shown to offer an empirically satisfactory and theoretically parsimonious account of two prominent types of coordinate ellipsis, in particular Forward Conjunction Reduction (FCR) and Gapping (including Long-Distance Gapping and Subgapping). They are analyzed as different manifestations of Òincremental updatingÓ Ñ efficient updating of only part of the existing sentential structure. Based on empirical data from Dutch and German, novel treatments are proposed for both types of clausal coordinate ellipsis. Two other forms of coordinate ellipsis Ñ SGF (ÒSubject Gap in Finite clauses with fronted verbÓ), and Backward Conjunction Reduction (BCR; also known as Right Node Raising or RNR) Ñ are shown to be incompatible with the notion of incremental updating. Alternative theoretical interpretations of these phenomena are proposed. The four types of clausal coordinate ellipsis Ñ SGF, Gapping, FCR and BCR Ñ are argued to originate in four different stages of sentence production: Intending (i.e. preparing the communicative intention), Conceptualization, Grammatical Encoding, and Phonological Encoding, respectively.

Abstract

We outline an algorithm capable of generating varied but natural sounding sequences of argument NPs in subordinate clauses of German, a semi-free word order language. In order to attain the right level of output flexibility, the algorithm considers (1) the relevant lexical properties of the head verb (not only transitivity type but also reflexivity, thematic relations expressed by the NPs, etc.), and (2) the animacy and definiteness values of the arguments, and their length. The relevant statistical data were extracted from the NEGRA–II treebank and from hand-coded features for animacy and definiteness. The algorithm maps the relevant properties onto “primary” versus “secondary” placement options in the generator. The algorithm is restricted in that it does not take into account linear order determinants related to the sentence’s information structure and its discourse context (e.g. contrastiveness). These factors may modulate the above preferences or license “tertiary” linear orders beyond the primary and secondary options considered here.

Abstract

In this paper we present a definition of Performance Grammar (PG), a psycholinguistically motivated syntax formalism, in declarative terms. PG aims not only at describing and explaining intuitive judgments and other data concerning the well–formedness of sentences of a language, but also at contributing to accounts of syntactic processing phenomena observable in language comprehension and language production. We highlight two general properties of human sentence generation, incrementality and late linearization,which make special demands on the design of grammar formalisms claiming psychological plausibility. In order to meet these demands, PG generates syntactic structures in a two-stage process. In the first and most important ‘hierarchical’ stage, unordered hierarchical structures (‘mobiles’) are assembled out of lexical building blocks. The key operation at work here is typed feature unification, which also delimits the positional options of the syntactic constituents in terms of so-called topological features. The second, much simpler stage takes care of arranging the branches of the mobile from left to right by ‘reading–out’ one positional option of every constituent. In this paper we concentrate on the structure assembly formalism in PG’s hierarchical component. We provide a declarative definition couched in an HPSG–style notation based on typed feature unification. Our emphasis throughout is on linear order constraints.

Abstract

[Seven one-page psycholinguistic sketches]

Abstract

Modern word processors begin to offer a range of facilities for spelling, grammar and style checking in English. For the Dutch language hardly anything is available as yet. Many commercial word processing packages do include a hyphenation routine and a lexicon-based spelling checker but the practical usefulness of these tools is limited due to certain properties of Dutch orthography, as we will explain below. In this chapter we describe a text editor which incorporates a great deal of lexical, morphological and syntactic knowledge of Dutch and monitors the orthographical quality of Dutch texts. Section 1 deals with those aspects of Dutch orthography which pose problems to human authors as well as to computational language sensitive text editing tools. In section 2 we describe the design and the implementation of the text editor we have built. Section 3 is mainly devoted to a provisional evaluation of the system.

Abstract

Incremental sentence generation imposes special constraints on the representation of the grammar and the design of the formulator (the module which is responsible for constructing the syntactic and morphological structure). In the model of natural speech production presented here, a formalism called Segment Grammar is used for the representation of linguistic knowledge. We give a definition of this formalism and present a formulator design which relies on it. Next, we present an object- oriented implementation of Segment Grammar. Finally, we compare Segment Grammar with other formalisms.

Abstract

It is an important feature of the human sentence production system that semantic and syntactic processes may overlap in time and do not proceed strictly serially. That is, the process of building the syntactic form of an utterance does not always wait until the complete semantic content for that utterance has been decided upon. On the contrary, speakers will often start pronouncing the first words of a sentence while still working on further details of its semantic content. An important advantage is memory economy. Semantic and syntactic fragments do not have to occupy working memory until complete semantic and syntactic structures for an utterance have been computed. Instead, each semantic and syntactic fragment is processed as soon as possible and is kept in working memory for a minimum period of time. This raises the question of how the sentence production system can maintain syntactic coherence across syntactic fragments. Presumably there are processes of "syntactic bookkeeping" which (1) store in working memory those syntactic properties of a fragmentary sentence which are needed to eliminate ungrammatical continuations, and (2) check whether a prospective continuation is indeed compatible with the sentence constructed so far. In reaction time experiments where subjects described, under time pressure, simple static pictures of an action performed by an actor, the second aspect of syntactic bookkeeping could be demonstrated. This evidence is used for modelling bookkeeping processes as part of a computational sentence generator which aims at simulating the syntactic operations people carry out during spontaneous speech.

Abstract

The psychological process of translating semantic into syntactic structures has dynamic properties such as the following. (1) The speaker is able to start pronouncing an utterance before having worked out the semantic content he wishes to express. Selection of semantic content and construction of syntactic form proceed partially in parallel. (2) The human sentence generator takes as input not only a specification of semantic content but also some indication of desired syntactic shape. Such indications, if present, do not complicate the generation process but make it easier. (3) Certain regularities of speech errors suggest a two-stage generation process. Stage I constructs the “syntactic skeleton” of an utterance; stage II provides the skeleton with morpho- honological information. An outline is given of the type of grammar which is used by a sentence generation system embodying these characteristics. The system is being implemented on a computer.