Abstract
During language understanding, people do not only rely on what they read or hear, but they also exploit implicit information. For example, when they process the expression ‘begin the book’, they understand it involves an event which is not explicitly mentioned (e.g. ‘begin reading the book’). This thesis looks at these constructions, known as logical metonymies, which combine an event-selecting verb and entity-denoting object and involve covert events. Logical metonymies are an interesting challenge for theories of lexical semantics: they need to be reconciled with compositionality, they require the integration of context (writers typically write books, students typically read them), and they lie at the interface between lexicon and world knowledge (is the information that books are read stored in our mental lexicon or in our world knowledge?). I critically analyze previous hypotheses on logical metonymy with regard to the answer they provide to two core problems: the source problem (what events are retrieved? what type of event knowledge is assumed?) and the trigger problem (why do some constructions trigger a metonymic interpretation and others do not?). Lexicalist approaches claim that the metonymy arises from a type clash between the event-selecting verb and an entity-denoting object, and posit complex lexical items, encoding event information about artifacts (e.g. book → read), to explain the recovery of covert events. Pragmatic-based approaches argue against the idea that lexical items have an internal structure, suggesting that covert events arise from the underspecification of a logical metonymy and are inferred via non-lexical knowledge. I look with particular attention at the role of event knowledge, which lexicalist approaches place in our mental lexicon, while pragmatic-based approaches place it in our world knowledge. I propose a third hypothesis, based on thematic fit and generalized event knowledge of typical events and their participants, which have been shown to guide efficient incremental processing: I argue that contextual elements cue generalized event knowledge, which plays a key role in determining the covert event for a logical metonymy. I explore this hypothesis from an interdisciplinary perspective, employing both psycholinguistic experiments and computational models, in order to seek converging evidence and confront it with the theoretical investigation. The results from the psycholinguistic experiments and from the computational (distributional) models support the hypothesis that covert event retrieval is guided by generalized event knowledge. I also employ the computational models to analyze previous experimental results and to explore the hypothesis that thematic fit, informed by generalized event knowledge, is ultimately responsible for the trigger of the logical metonymy. I then report on more psycholinguistic evidence showing that a notion of type is indeed necessary to account for differences between metonymic and non-metonymic constructions, and that both type and thematic fit play a role in logical metonymy interpretation. Lastly, I argue for a context-sensitive model of logical metonymy interpretation that exploits an information-rich lexicon, but needs to rethink the notion of type and reconcile it with the notion of thematic fit.
Alessandra Zarcone
Professor of Language Technologies and Cognitive Assistants
Computational linguist with a background in NLP and in psycholinguistics, working on AI, NLP and human-machine interaction.