An Experimental Investigation of Presupposition Projection in Conditional Sentences

Conditional sentences with a presupposition trigger in the consequent— if φ, then ψ_p—show peculiar projection properties. That is, the entire sentence suggests that p in some cases, and that φ → p in other cases. We report on the results of two sentence-picture matching experiments that indicate that the perceived dependence of the presupposition p on the antecedent φ affects which inference is made. The results are also used to compare two major theories of presupposition projection, and we argue that the theory that postulates φ → p as the presupposition of all conditional sentences explains the results more straightforwardly than its competitor.