In this paper we address some key issues in the psychology of word meaning, and thereby motivate a Sense Generation approach to the diversity of senses that a word may have. We note that an adequate account must allow for the flexibility and specificity of senses, and must also make appropriate distinctions between default and non-default senses of a word, and between different senses for vague and ambiguous words. W e then discuss two central components of a theory of sense. Firstly, lexons, the stable representations, in a "mental lexicon", of word meanings; secondly, senses, the mentally represented descriptions associated with particular uses of words. W e argue that the crucial issues in accounting for the diversity of sense, are: the number of lexons we need to postulate, and the relationship between the contents of those lexons and their associated senses. Sense Selection accounts, of which we distinguish Strong and Weak versions, both of which find considerable support in the cognitive science Literature, fail to Account for the flexibility and specificity of senses in a way that is consonant with linguistic evidence regarding the ambiguity of words, and psychological evidence regarding the coherence which underlies their use. W e will show how the Sense Generation approach, by positing a nonmonotonic relationship between lexons and their senses, respects these considerations. W e sketch this approach, and finally note some of its promising implications for other aspects of word meaning.

We report work in progress on the computational modelling of a theory of concepts and concept combination. The sense generation approach to concepts provides a perspicuous way of treating a range of recalcitrant concept combinations: privative combinations {e.g., fake gun, stone lion, apparent friend). We argue that a proper treatment of concept combination must respect important syntactic constraints on the combination process, the simplest being the priority of syntactic modifier over the head in case of conflicts. We present a model of privative concept combinations based on the sense generation approach. The model was developed using cogent, an object-oriented modelling environment designed to simplify and clarify the implementation process by minimising the 'distance' between the box/arrow 'language' of psychological theorising and the theory's implementation. In addition to simple privatives (i.e., ones with a single modifier, like fake gun) the model also handles iterated, or complex, privative combinations (i.e., ones with more than one modifier, like fake stone lion), and reflects their associated modification ambiguities. We suggest that the success of this model reflects both the utility of COGENT as a modelling framework and the adequacy of sense generation as a theory of concept combination.

Kripke (1972) and Putnam (1975a; 1975b) have argued forcefully for the philosophical view of word meaning known as rigid designation. While certain psychological studies have appeared to offer this view support (Keil, 1986; Rips, 1989), we argue that these have not provided an exhaustive evaluation. In particular, the original discussions of Kripke and Putnam reveal that their view rests on an explicit appeal to intuition concerning word use in a range of different scenarios. The study reported here investigates word use under three such types of scenarios, for a variety of natural kind terms, by investigating subjects' judgements of truth or falsity for a range of statement types. W e argue that the results obtained indicate that the intuition on which rigid designation rests is not one which is generally true of agents' language use. Further, we obtam patterns of apparent contradiction which appear strictly inconsistent with rigid designation and which require an account of word meaning which allows that the sense of words may vary systematically with context (Franks & Braisby, 1990).