Cognitive models of the time-varying lexicon

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Modern artificial intelligent systems such as IBM Watson or Apple Siri have shown promise of understanding human language. However, a fundamental property of human language challenges the key assumptions in these technologies: A natural language system typically relies on a fixed lexicon, in contrast with the human lexicon that varies over time. In particular, words have shown remarkable fluidity in meaning over time, e.g., gay ('happy''homosexual'), grasp ('action''understanding'). What are the cognitive foundations that make this possible? Addressing this question will be centrally important to the understanding of the creative nature of language and inform future AI research in the design of a human-like lexicon.Compared to other aspects of language change such as in grammar or sound where there are rich formal characterizations, historical meaning change is least understood. On one hand, cognitive theories of meaning change typically suffer from the dual challenge of principled formalization and critical assessment at scale. On the other hand, although recent work in computational linguistics has shown promise in the detection of novel word meanings, such work does not typically specify the cognitive mechanisms that give rise to emerging meanings. This research program is situated at bridging these fields by developing cognitively grounded models that predict the evolution of word meanings. It will pursue the long term objective of developing a formal account of the evolution of the lexicon, with the short-term emphasis on understanding the principled mechanisms of historical meaning change.The approach will build upon my background in machine learning and computational cognitive science, and recent research expertise in this area. Specifically, it will draw on a combination of cognitive linguistic theories and formal tools from computer science, and engage rich empirical data ranging from large open-access resources including historical corpora, dictionaries and cross-linguistic lexicons, to behavioral experiments. The outcomes will contribute to theories and modeling of the cognitive principles and mechanisms that support meaning change over time, explored in three sets of proposed projects at the incremental levels of individual words, semantic fields, and the lexicon. The interdisciplinary nature of this research program will have a significant impact on the fields of cognitive science, linguistics, and artificial intelligence. As such, it will train both scholars for basic scientific research in academia and computational scientists who will contribute to industry and beyond.