Context effects in similarity judgments.

Tversky's (1977) famous demonstration of a diagnosticity effect indicates that the similarity between the same two stimuli depends on the presence of contextual stimuli. In a forced choice task, the similarity between a target and a choice, appears to depend on the other choices. Specifically, introducing a distractor grouped with one of the options would reduce preference for the grouped option. However, the diagnosticity effect has been difficult to replicate, casting doubt on its robustness and our understanding of contextual effects in similarity generally. We propose that the apparent brittleness of the diagnosticity effect is because it is in competition with an opposite attraction effect. Even though in both the similarity and decision-making literatures there are indications for such a competition, we provide the first direct experimental demonstration of how an attraction effect can give way to a diagnosticity one, as a distractor option is manipulated. (PsycInfo Database Record (c) 2021 APA, all rights reserved).