Conditional reasoning with negations: Matching bias and implicit versus explicit affirmation or denial

We report a study examining the effect of implicit affirmation and denial i n reasoning with negative conditionals. Four conditional inference problems are constructed by an affirmation of the antecedent (Modus Ponens, MP), an affirmation of the consequent (AC), a denial of the antecedent (DA) or a d enial of the consequent (Modus Tollens, MT). Depending on the presence of n egations in the conditionals, these problems were set with an implicit or e xplicit type of referencing (i.e, affirmation or denial). Implicit affirmat ion and denial introduced matching bias effects: When the topic of the cate gorical premise (e.g., the letter B) does not match the topic of the condit ional's referred clause (e.g., If there is a letter A), participants made f ewer conditional inferences. The effect of implicit affirmation (e.g., 'the letter B' affirms an antecedent 'if there is no A') was larger than the ef fect of implicit denial. and reading times (obtained by eye movement record ings) showed that implicit affirmation problems rook longer to solve wherea s implicit denial problems were solved faster than the explicit denial prob lems. Both findings are novel and we hypothesize that the larger effect on implicit affirmation of a negative (as compared to implicit denial of an af firmative) is due to uncertainty in considering a single instance sufficien t to affirm the: entire contrast class of that negative.