Four experiments were performed to test the relationship between instructionally derived knowledge and practice in the use of a simple device. Using a derivative of Kieras and Bovair's (1984) device, we show that different subjects can be given instructions that convey equivalent information but that lead to crossovers in the time to perform different tasks (i.e., one task is easier with one set of instructions, a second task is easier with other instructions). Experiment 1 shows that the performance crossover between question types perseveres when subjects relinquish the instructions, after they have been committed to memory. Experiment 2 shows that the performance crossover perseveres over considerable experience using the device. Experiment 3 shows that the crossover can disappear if sufficient practice is given with the particular question types. Experiments 2 and 3 taken together suggest that subjects may only be able to overcome the computational disadvantages of their initial instructional material by adopting task-specific strategies. Experiment 4 shows that when new problems are introduced after the point at which the crossover disappears then a new crossover appears, implying that, even with extended practice of operating the device and solving problems on the device, some features of the initial instructional device description are preserved and continue to determine the users' behavior. We argue that a definition of internalization coupled with Anderson's (1983, 1987) ACT* theory of skill acquisition provides a good account of these results.