Abstract
Similarity is a fundamental concept in cognition. In 1977, Amos Tversky published a highly influential feature-based model of how people judge the similarity between objects. The model highlights the context-dependence of similarity judgments, and challenged geometric models of similarity. One of the context-dependent effects Tversky describes is the diagnosticity principle. The diagnosticity principle determines which features are used to cluster multiple objects into subgroups. Perceived similarity between items within clusters is expected to increase, while similarity between items in different clusters decreases. Here, we present two pre-registered replications of the studies on the diagnosticity effect reported in Tversky (1977). Additionally, one alternative mechanism that has been proposed to play a role in the original studies, an increase in the choice for distractor items (a substitution effect, see Medin et al., 1995), is examined. Our results replicate those found by Tversky (1977), revealing an average diagnosticity-effect of 4.75%. However, when we eliminate the possibility of substitution effects confounding the results, a meta-analysis of the data provides no indication of any remaining effect of diagnosticity.
Highlights
In 1977, Amos Tversky published a highly influential paper on features of similarity
Tversky illustrates the diagnosticity of features with the following example: “the feature ‘real’ has no diagnostic value in a set of actual animals since it is shared by all actual animals and cannot be used to classify them
Based on the results of the categorization task, participants in condition 1 were expected to be more likely to indicate the neutral face (a) being similar to the frowning face (b) as compared to participants in condition 2, but this was not the case (38/12, 29.9% in condition 1, 46/127, 36.2% in condition 2, the diagnosticity effect was calculated by subtracting the choiceproportion in condition 2 from the choice proportion in condition 1 resulting in a diagnosticity effect of −6.30%, χ2(1, N = 254) = 1.14, p = 0.29, Cramer’s V = 0.067
Summary
In 1977, Amos Tversky published a highly influential paper on features of similarity. Tversky (1977) argues that the salience of features is determined by intensive and diagnostic factors. Tversky illustrates the diagnosticity of features with the following example: “the feature ‘real’ has no diagnostic value in a set of actual animals since it is shared by all actual animals and cannot be used to classify them. This feature, acquires considerable diagnostic value if the object set is extended to include legendary animals, such as a centaur, a mermaid, or a phoenix” This feature, acquires considerable diagnostic value if the object set is extended to include legendary animals, such as a centaur, a mermaid, or a phoenix” (Tversky, 1977, p. 342)
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