Comparing Measures of Individual Differences in Performance of Conditional Reasoning* Gloria Seoane, María Dolores Valiña, María José Ferraces & Montserrat Martín University of Santiago de Compostela (Spain) Introduction The study of thinking and reasoning is a topic of central interest for economists, anthropologists, logicians, pedagogues and of course for psychologists. A central problem in the experimental investigation in Psychology is to describe how people think and reason deductively and inductively. There are three fundamental theoretical approaches to deductive reasoning in the Cognitive Psychology: mental logic, mental models and pragmatic schemas. ________________ * This work was presented at 10 th EUROPEAN MEETING OF THE PSYCHOMETRIC SOCIETY, celebrated in Santiago de Compostela, Spain (15-18th July, 1997).