Drawing inferences from the presuppositions and implications of affirmative and negative sentences

Abstract

This study examined the effects of negation on how people make use of information in the presuppositions and implications of sentences. Subjects were timed as they made true-false judgments of sentences like If John forgot to let the dog out, then the dog is supposed to be in. The verbs were either positive (for example, remember) or inherently negative (forget); the conclusions interrogated either presuppositions (the dog is supposed to be out) or implications (the dog is out). Subjects found it easier to verify positive components as true, but negative components as false. This happened regardless of the polarity (positive or negative) of the parent sentence. Also, subjects took longer on negative verbs, but by an equal amount on both components, even though such negation does not logically affect presuppositions. This suggests that people may examine implications before presuppositions regardless of which component is interrogated.