Proceedings of the Annual Meeting of the Cognitive Science Society

In the last decades there was a shift from more logically in-spired theories describing human reasoning towards the newparadigm of probabilistic approaches. One of the most promi-nent models for syllogistic reasoning is the Probability Heuris-tics Model (PHM) which has been formulated based on fiveheuristics. The contribution of this article is: (i) to provide ananalysis of different formalizations of the PHM, (ii) to exam-ine the impact of each heuristic, and (iii) to identify possibleviolations of underlying assumptions in present implementa-tions. A systematic analysis of the model parameters shows asurprising variation in parameter values across experiments. ABayesian modeling approach explains this variance of param-eters. Implications for probabilistic approaches are discussed.