Do Frequency Representations Eliminate Conjunction Effects? An Exercise in Adversarial Collaboration

The present article offers an approach to scientific debate called adversarial collaboration. The approach requires both parties to agree on empirical tests for resolving a dispute and to conduct these tests with the help of an arbiter. In dispute were Hertwig's claims that frequency formats eliminate conjunction effects and that the conjunction effects previously reported by Kahneman and Tversky occurred because some participants interpreted the word “and” in “bank tellers and feminists” as a union operator.

Hertwig proposed two new conjunction phrases, “and are” and “who are,” that would eliminate the ambiguity. Kahneman disagreed with Hertwig's predictions for “and are,” but agreed with his predictions for “who are.” Mellers served as arbiter. Frequency formats by themselves did not eliminate conjunction effects with any of the phrases, but when filler items were removed, conjunction effects disappeared with Hertwig's phrases.

Kahneman and Hertwig offer different interpretations of the findings. We discuss the benefits of adversarial collaboration over replies and rejoinders, and present a suggested protocol for adversarial collaboration.