What can the conjunction fallacy tell us about human reasoning?

Abstract

In this chapter, I will briefly summarize and discuss the main results obtained from more than three decades of studies on the conjunction fallacy (hereafter CF) and will argue that this striking and widely debated reasoning error is a robust phenomenon that can systematically affect laypeople’s as much as experts’ probabilistic inferences, with potentially relevant real-life consequences. I will then introduce what is, in my view, the best explanation for the CF and indicate how it allows the reconciliation of some classic probabilistic reasoning errors with the outstanding reasoning performances that humans have been shown capable of. Finally, I will tackle the open issue of the greater accuracy and reliability of evidential impact assessments over those of posterior probability and outline how further research on this topic might also contribute to the development of effective human-like computing.