Necessity, sufficiency, and perspective effects in causal conditional reasoning

A growing body of research indicates that in causal conditional reasoning, the conclusion that P is necessary for Q is suppressed where alternative co nditions for Q are available. Similarly, the conclusion that P is sufficien t for Q is suppressed where disabling conditions for P or additional requir ements for Q are available. This paper describes experiments in which these factors were used to produce "perspective effects" in causal contexts that appear identical to the perspective effects found in previous research wit h deontic tasks. It is therefore proposed that deontic perspective effects are themselves also attributable to the influence of pragmatic factors upon perceived necessity and sufficiency. A generalized theory based on a modif ication of the mental model theory of deontic reasoning is presented, which accounts for perspective effects across the two domains.