Abstract
The present paper addresses the basis for suppression effects observed in conditional inference. Previous research has shown that when an additional premise is included, the invalid inferences “denial of the antecedent” and “affirmation of the consequent” are suppressed (Rumain, Connell, & Braine, 1983). Byrne (1989) has shown that a similar suppression effect can occur in valid inferences (modus Ponens and modus Tollens). We briefly present the results of a series of experiments that show that strategic factors related to task and presentation format may affect the presence of suppression effects. We also present an introspective experiment (thinking aloud procedure) that clarifies the usage of two different strategies, the integration and the amendment strategy. The results are discussed with respect to the mental logic and mental model theories of reasoning.