Behavioral and Brain Sciences

Table of Contents - 2007 - Volume 30, Issue 03  

Open Peer Commentary

The role of representation in Bayesian reasoning: Correcting common misconceptions

Gerd Gigerenzera1 and Ulrich Hoffragea2

a1 Max Planck Institute for Human Development, Lentzeallee 94, 14195 Berlin, Germany gigerenzer@mpib-berlin.mpg.de

a2 Ecole des Haute Etudes Commerciales (HEC), University of Lausanne, Batiment Internef, 1015 Lausanne, Switzerland. Ulrich.Hoffrage@unil.ch

Abstract

The terms nested sets, partitive frequencies, inside-outside view, and dual processes add little but confusion to our original analysis (Gigerenzer & Hoffrage 1995; 1999). The idea of nested set was introduced because of an oversight; it simply rephrases two of our equations. Representation in terms of chances, in contrast, is a novel contribution yet consistent with our computational analysis – it uses exactly the same numbers as natural frequencies. We show that non-Bayesian reasoning in children, laypeople, and physicians follows multiple rules rather than a general-purpose associative process in a vaguely specified “System 1.” It is unclear what the theory in “dual process theory” is: Unless the two processes are defined, this distinction can account post hoc for almost everything. In contrast, an ecological view of cognition helps to explain how insight is elicited from the outside (the external representation of information) and, more generally, how cognitive strategies match with environmental structures.

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