The transformational theory of similarity suggests that whenjudging similarity, people are sensitive to the number of trans-formation operations needed to make two compared repre-sentations match. Although this theory has been influential,little is known about how transformations are learned andto what extent learned transformations affect similarity judg-ments. This paper presents two experiments addressing thesequestions, in which people learned categories defined by atransformation. In Experiment 1, when the transformationswere directly visible, people had no trouble learning and ap-plied their knowledge to similarity and categorization judg-ments involving previously unseen items. In Experiment 2,the task required transformations to be inferred rather than ob-served. People were still able to learn the categories, but inthis more difficult case ratings were less strongly affected bytraining. Overall, this work suggests that newly learned trans-formations can impact similarity judgments but the salience ofthe transformation has a large impact on transfer.