Experimental investigations of the typology of presupposition triggers

The behaviour of presupposition triggers in human language has been extensively studied and given rise to many distinct theoretical proposals. One intuitively appealing way of characterising presupposition is to argue that it constitutes backgrounded meaning, which does not contribute to updating the conversational record, and consequently may not be challenged or refuted by discourse participants. However, there are a wide range of presupposition triggers, some of which can systematically be used to introduce new information. Is there, then, a clear psychological distinction between presupposition and assertion? Do certain expressions vacillate between presupposing and asserting information? And is information backgrounding a categorical or a gradient phenomenon? In this paper we argue for the value of experimental methods in addressing these questions, and present a pilot study demonstrating backgrounding effects of presupposition triggers, and suggesting their gradience in nature. We discuss the implications of these findings for theoretical categorisations of presupposition triggers.