Constructivist Development of Grounded Construction Grammar

Constructivist Development of Grounded Construction Grammars Luc Steels University of Brussels (VUB AI Lab) SONY Computer Science Lab - Paris 6 Rue Amyot, 75005 Paris steels@arti.vub.ac.be Abstract The paper reports on progress in building com- putational models of a constructivist approach to language development. It introduces a formalism for construction grammars and learning strategies based on invention, abduction, and induction. Ex- amples are drawn from experiments exercising the model in situated language games played by embod- ied artificial agents. 1 Introduction The constructivist approach to language learning proposes that ”children acquire linguistic compe- tence (...) only gradually, beginning with more concrete linguistic structures based on particular words and morphemes, and then building up to more abstract and productive structures based on various types of linguistic categories, schemas, and constructions.” (TomaselloBrooks, 1999), p. 161. The approach furthermore assumes that language development is (i) grounded in cognition because prior to (or in a co-development with language) there is an understanding and conceptualisation of scenes in terms of events, objects, roles that objects play in events, and perspectives on the event, and (ii) grounded in communication because language learning is intimately embedded in interactions with specific communicative goals. In contrast to the nativist position, defended, for example, by Pinker (Pinker, 1998), the constructivist approach does not assume that the semantic and syntactic categories as well as the linking rules (specifying for example that the agent of an action is linked to the subject of a sentence) are universal and innate. Rather, se- mantic and syntactic categories as well as the way they are linked is built up in a gradual developmen- tal process, starting from quite specific ‘verb-island constructions’. Although the constructivist approach appears to explain a lot of the known empirical data about child language acquisition, there is so far no worked out model that details how constructivist language de- velopment works concretely, i.e. what kind of com- putational mechanisms are implied and how they work together to achieve adult (or even child) level competence. Moreover only little work has been done so far to build computational models for han- dling the sort of ’construction grammars’ assumed by this approach. Both challenges inform the re- search discussed in this paper. 2 Abductive Learning In the constructivist literature, there is often the im- plicit assumption that grammatical development is the result of observational learning, and several re- search efforts are going on to operationalise this ap- proach for acquiring grounded lexicons and gram- mars (see e.g. (Roy, 2001)). The agents are given pairs with a real world situation, as perceived by the sensori-motor apparatus, and a language utterance. For example, an image of a ball is shown and at the same time a stretch of speech containing the word “ball”. Based on a generalisation process that uses statistical pattern recognition algorithms or neural networks, the learner then gradually extracts what is common between the various situations in which the same word or construction is used, thus progres- sively building a grounded lexicon and …

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