What can the conjunction fallacy tell us about human reasoning?

This chapter briefly summarizes some the main results obtained from more than three decades of studies on the conjunction fallacy. It shows that this striking and widely discussed reasoning error is a robust phenomenon that can systematically affect the probabilistic inferences of both laypeople and experts, and it introduces an explanation based on the notion of evidential impact in terms of contemporary Bayesian confirmation theory. Finally, the chapter tackles the open issue of the greater accuracy and reliability of impact assessments over posterior probability judgments and outlines how further research on the role of evidential reasoning in the acceptability of explanations might contribute to the development of effective human-like computing.