Effect of directionality in conditionals.

Abstract

Two experiments showed that the degree of difficulty of conditionals (conditionals with one premise versus conditionals with two premises) produces different kinds of directional effect. In experiment 1, where the difficulty was low, there was a directional effect for the conditional “if p, then q”: participants select more forward (from p to q) than backward inferences (from q to p). In experiment 2, where the difficulty was high, there was a forward directional effect for the conditionals “if p, then q”, a backward directional effect for the conditional “only if q” and no directional effects for the conditional “p if q”. We propose that the directional effects in these conditionals are a result of application of the principle of “first mention” (Gernsbacher, 1990) and of the “Hypothesis of the hypothetical value” (Evans, 1993; Grosset and Barrouillet, 2003).