What information do people extract in the course of category learning? And how does training affect this process? The current study addressed these questions by examining the effects of training on the outcome of category learning in 4- to 5-year-olds and adults. In two experiments, participants were trained on either a classification task or an inference task and then tested with categorization and recognition tasks. The categorical information (i.e., deterministic and probabilistic features) was explicitly given to participants in Experiment 1 but not in Experiment 2. Results with adults replicate previous findings indicating that participants form different representations in the course of classification and inference training (rule-based representation in the former case and similarity-based representations in the latter case). In contrast, regardless of the type of training, young children form similarity-based representations.