Abstract

Gigerenzer’s ‘external validity argument’ plays a pivotal role in his critique of the heuristics and biases research program (HB). The basic idea is that (a) the experimental contexts deployed by HB are not representative of the real environment and that (b) the differences between the setting and the real environment are causally relevant, because they result in different performances by the subjects. However, by considering Gigerenzer’s work on frequencies in probability judgments, this essay attempts to show that there are fatal flaws in the argument. Specifically, each of the claims is controversial: whereas (b) is not adequately empirically justified, (a) is inconsistent with the ‘debiasing’ program of Gigerenzer’s ABC group. Therefore, whatever reason we might have for believing that the experimental findings of HB lack experimental validity, this should not be based on Gigerenzer’s version of the argument.