(Invited Talk) Clueless: Explorations in Unsupervised, Knowledge-Lean Extraction of Lexical-Semantic Information

Why is it that if you know I’ll give a silly talk, it follows that you know I’ll give a talk, whereas if you doubt I’ll give a good talk, it doesn’t follow that you doubt I’ll give a talk? This pair of examples shows that the word “doubt” exhibits a special but prevalent kind of behavior known as downward entailingness — the licensing of reasoning from supersets to subsets, so to speak, but not vice versa. The first project I’ll describe is to identify words that are downward entailing, a task that promises to enhance the performance of systems that engage in textual inference, and one that is quite challenging since it is difficult to characterize these items as a class and no corpus with downward-entailingness annotations exists. We are able to surmount these challenges by utilizing some insights from the linguistics literature regarding the relationship between downward entailing operators and what are known as negative polarity items — words such as “ever” or the idiom “have a clue” that tend to occur only in negative contexts. A cross-linguistic analysis indicates some potentially interesting connections to findings in linguistic typology.