A recent meta-analysis carried out by Khemlani and Johnson-Laird showed that the conclusions drawn by humans in psychological experiments about syllogistic reasoning deviate from the conclusions drawn by classical logic. Moreover, none of the current cognitive theories predictions fit the empirical data. In this paper a Computational Logic analysis clarifies seven principles necessary to draw the inferences. We propose a modular approach towards these principles and show how human syllogistic

more »

... asoning can be modeled under a new cognitive theory, the Weak Completion Semantics.