Oberauer, Klaus (University of Potsdam, Germany) - Conditionals: Interpretation and Inferences


Project:	Conditionals: Interpretation and Inferences
Researchers:	Klaus Oberauer, Katrin Fischer, Andrea Weidenfeld, and Sonja Geiger
Duration:	since 2000
Support:	Deutsche Forschungsgemeinschaft (DFG)
Description:	Conditionals are ubiquitous in our everyday thinking and talking (e.g., "if I don't catch the train, I'll come late to the seminar") as well as in scientific reasoning (e.g., "if list length increases, recall of the list decreases"). The inferences people draw from conditionals as premises depend on the interpretation a conditional statement is given. The dominant theory of deductive reasoning, the theory of mental models (Johnson-Laird & Byrne), assumes that conditionals are represented as truth-functional, that is as a set of possible worlds for which the conditional is true. These possible worlds are represented as models. An alternative position is that conditionals are understood as expressing a high conditional probability of the consequent, given the antecedent. In a series of experiments, we found that a majority of participants interpreted conditionals in line with the probabilistic view, whereas a minoritiy showed response patterns compatible with a version of mental model theory. We are currently investigating what lies behind these two psychological meanings of conditionals.
	In addition, we investigate how people reason from conditional premises. We developed a causal path model predicting the acceptance rates for the logically valid inferences from conditional premises (modus ponens and modus tollens). The model integrates ideas from probabilistic views (i.e., that the likelihood of accepting inferences depends on the degree of belief in the conditional itself, which in turn depends on the conditional probability of the consequent, given the antecedent) with ideas from the theory of mental models (i.e., that people reject inferences when they can retrieve a counterexample from their knowledge base).
Publications:	Oberauer, K. & Wilhelm, O. (2003). The meaning(s) of conditionals - conditional probabilities, mental models, and personal utilities. Journal of Experimental Psychology: Learning, Memory, and Cognition, 29, 680-639
	Oberauer, K., Weidenfeld, A., & Hörnig, R. (in press). Logical reasoning and probabilities. A comprehensive test of Oaksford and Chater (2001). Psychonomic Bulletin & Review

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