In ACT-R a retrieval makes a chunk stronger so it is more likely to be recalled the next time. However, in some cases this is problematic. For example, if you are recalling different types of animals and the tiger has the highest activation it will be recalled first, and also second, and third, and so on. So there is a way to tell a production to retrieve a chunk that has not recently been recalled. In this model a sandwich maker has several different orders and makes them in the order he recalls them