On the reality of cognitive illusions

The study of heuristics and biases in judgment has been criticized in several publications by G.<br>Gigerenzer, who argues that "biases are not biases" and "heuristics are meant to explain what does<br>not exist" (1991, p. 102). This article responds to Gigerenzer's critique and shows that it misrepresents<br>the authors' theoretical position and ignores critical evidence. Contrary to Gigerenzer's central<br>empirical claim, judgments of frequency - not only subjective probabilities - are susceptible to large<br>and systematic biases. A postscript responds to Gigerenzer's (1996) reply.