Syllogistic inference

This paper reviews current psychological theories of syllogistic inference and establishes that despite their various merits they all contain deficiencies as theories of performance. It presents the results of two experiments, one using syllogisms and the other using three-term series problems, designed to elucidate how the arrangement of terms within the premises (the figure’ of the premises) affects performance. These data are used in the construction of a theory based on the hypothesis that reasoners construct mental models of the premises, formulate informative conclusions about the relations in the model, and search for alternative models that are counterexamples to these conclusions. This theory, which has been implemented in several computer programs, predicts that two principal factors should affect performance: the figure of the premises, and the number of models that they call for. These predictions were confirmed by a third experiment. I, boduction The ability to make deductions that depend on quantifiers is a prerequisite for everyday thinking and for mathematics and science. Quantifiers include *We thank Stefania Bandini, M. Caterina Gallo, Michele Neri, Giuliano Geminiani and Alison BUack for their technical assistance, and Patrizia Tabossi for carrying out a replication of Experiment 2. We are also grateful to Steve Hard, Antonella Carassa and Marco Colombetti for their help in devising the colmputer programs, to A.R. Jonckheere for stimulating statistical advice, and to Martin Braine, Earl 9. Hunt, Jane Oakhill and RUSS Revlin for discussion and criticisms of earlier versions of this paper. Part of our research was supported. by grants from the Social Science Research Council and the European Training Programme. Reprint requests should be sent to P.N. Johnson-Laird, MRC Applied Psychology Unit, 15 Chaucer Road, Cambridge CB2 2EF, U.K. 0010~0277M/$18.80 0 Elsevier Sequoia/Printed in The Netherlands