Reversing the Similarity Effect in Stock‐Outs: A New Look at a Renowned Phenomenon in Consumers’ Brand Switching Behavior

Over 40 years of research has established the robustness of the similarity effect (SE; Tversky, 1972 ), which states that the introduction of new options into choice sets predominantly reduces the choice share of similar options. The present work examines whether the SE systematically reverses when real brands are excluded from assortment subsets, as is the case with stock‐outs in real purchase decisions. To this end, within‐subject decisions are examined under certain out‐of‐stock (OOS) conditions in an enhanced experimental design that resembles real shopping environments. Specifically, unforced choices of experienced consumers, inclusive of real payments, are observed for products in online transactions. The results of two studies corroborate the existence of a reserved SE. Specifically, the OOS‐induced switching patterns systematically refute the assumptions of classic economic theory, since consumers disproportionately switch to alternatives which are similar to the unavailable item in contrast to dissimilar substitutes. Finally, managerial implications and potential directions for follow‐up research in the general domain of marketing are deduced.