SUPPRESSION OF VALID INFERENCES - SYNTACTIC VIEWS, MENTAL MODELS, ANDRELATIVE SALIENCE

Byrne (1989) had demonstrated that although subjects can make deductiv ely valid inferences of the modus ponens and modus tollens forms, thes e valid inferences can be suppressed by presenting an appropriate addi tional premise ''If R then Q'' with the original conditional ''If P th en Q''. This suppression effect challenges the assumption of all synta ctic theories of conditional reasoning that formal rules of inference such as modus ponens is part of mental logic. This paper argues that b oth the syntactic and the mental model accounts of the suppression eff ect are inadequate because they fail to give a principled account of t he critical interpretive component involved in reasoning. In contrast, the relative salience model proposed in this study emphasized the cen trality of the interpretative processes with the critical component be ing the relative salience of premises as judged by subjects on the bas is of their prior knowledge activated in particular problem situations . Using 120 under-graduates and 120 policemen as subjects, predictions from the model were tested and confirmed in a suppression paradigm an d evidence of convergent validity for the construct of salience were o btained. The results cannot be reconciled with either the syntactic vi ew or the mental model view that have dominated theories of conditiona l reasoning.