Unless: an experimental approach

Abstract

The semantics of unless has posed a challenge for compositional theories of semantics, and its role as a restrictor of quantifiers is a source of empirical as well as theoretical controversy. We report on an experiment which tests the predictions of the prominent “exceptive” account of unless, in particular with respect to how it differs from if not. Our results reveal categorical as well as graded patterns of difference between the two conditionals. These patterns falsify previous accounts and motivate a new theoretical picture in which the compositionality issue does not arise, and presupposition and implicature play a central role.