Published online by Cambridge University Press: 01 January 2025
On the basis of the idea of common elements to account for similarity, Restle [1959] developed a set-theoretical model on the generation of similarity judgments. Restle differentiates between his “more qualitative discussion” (p. 207), regarding stimuli as sets of elements and using no geometric concepts or assumptions, and metric quantitative developments of similarity, regarding stimuli as points in a geometric space. To the latter we can count the additive difference model of Beals, Krantz, & Tversky [1968] and Tversky & Krantz [1970].
Despite these differences the two models lead to the same conclusions on the characteristics of similarity judgments.
The authors would like to express their appreciation to Frank Restle for his very helpful comments on parts of this work.