Moderators of the feature-positive effect in abstract hypothesis-evaluation tasks.

Three studies using abstract materials tested possible moderators of the feature-positive effect in hypothesis evaluation whereby people use the presence of features more than their absence to judge which of 2 competing hypotheses is more likely. Drawing on a distinction made in visual perception research, we tested whether the feature-positive effect emerges both when using nonsubstitutive features, which can be removed without replacement by other features, and substitutive features, the absence of which implies the presence of other features (e.g., the colour red, the absence of which entails the presence of another colour). Furthermore, we tested whether presenting to participants both the clue occurrence probabilities (which are needed to consider clue presence) and their complements (which are needed to gauge the impact of the absent clues) decreased the feature-positive effect. The results showed that regardless of the type of feature (i.e., nonsubstitutive vs. substitutive), participants provided more responses consistent with an evaluation of the subset of present clues compared to all other kinds of responses. However, the use of substitutive features combined with an explicit presentation format of probabilistic information had a debiasing effect. Furthermore, the use of substitutive features negated participant sensitivity to the rarity of clues, whereby the feature-positive effect decreased when there was one absent clue and two present clues for problems in which the exclusive consideration of the presence of features did not suggest the correct response.