Directed forgetting in problem solving

In two experiments, we investigated intentional forgetting of problem-solving routines by adapting the list method of directed forgetting. In Experiment 1, participants practiced solving water-jar problems (Luchins, 1942). After working on a first series of problems that all could be solved by the same formula, one group of participants was instructed to forget the so-far presented items because these, allegedly, had only served as a warm-up, whereas another group did not receive a forget instruction. After practicing a different routine in a second series of problems, participants solved test problems that either could be solved by the formula previously practiced in the first or in the second series of problems. All test problems alternatively could be solved by a more direct formula. The forget instruction significantly reduced the number of test problems solved by the formula of the first series of practice problems. In Experiment 2, participants subsequently practiced two solution formulas in two series of to-be-solved anagrams. Here, a forget instruction regarding the first series of practice anagrams reduced solution speed for test anagrams that had to be solved by the same formula as the to-be-forgotten practice anagrams. Thus, in both experiments, participants relied less on a practiced routine after they had been instructed to intentionally forget the episode of acquiring that routine.