META-PROPOSITIONAL REASONING ABOUT THE TRUTH OR FALSITY OF PROPOSITIONS

A combination of premises such as ''Person A asserts that if and only if he's a liar, then person B is a liar'' and ''Person B asserts that person A is a truth-teller'', with the question what the status of per sons A and B might be (truth-teller or liar), elicits meta-proposition al reasoning, that is, reasoning about the truth and falsity of propos itions. Both an inference rule and a mental models approach have been proposed to explain for meta-propositional reasoning. These proposals are compared to one another with respect to the strategies that people use, and this suggests that the proposed strategies are to a large ex tent ad hoc amendments to either theory. A review of a series of studi es (Schroyens, 1995), controlling some confounding aspects in previous research, gives little evidence for a specific short-cut strategy tha t hinges on making backwards inferences. This counters the original pr oposal of Johnson-Laird and Byrne (1990) and recent corroborations of this strategy (Byrne & Handley, 1997; Schroyens, Schaeken, & d'Ydewall e, 1995). Other findings of our studies, however, indicate that, relat ive to the starting hypothesis by which one enters the formal structur e of the problems, reasoners do not always engage in an exhaustive sea rch strategy. This counters Rips (1989, 1990a) rule-based model, but i s in accordance with the mental model theory's principle that a valida ting search for counter-examples is carried out by default but is not invariably complete.