A related problem arises when poeple approach a problem in a sensible way but then, as they start to work on the problem, get locked into a particular line of thinking. In this case, people can end up being the victim of their own assumptions, rigidly following a path that no longer serves them well. Some investigators speak of a problem-solving set - the collection of beliefs and assumptions a person makes about a problem - with the notion that once the person has a set, it is difficult for him to shift to a new one. Other investigators use the term Einstellung, the German word for "attitude", to describe the problem-solver's perspecitve. The effects of Einstelling are easy to demonstrate, including data drawn from the so-called water-jar problem. In this problem, you are given three jars. Your task is to pour exactly 5 ounces of water into the bucket. How would you do it? Once participants have solved this problem, we give them a second and third problem. The series of problems is carefully designed such that all can be solved in the same way. After solving four problems of this form, participants are given one more problem, participants generally solve this problem the same way they have solved the previous problems. They apparently fail teo see that a different, more direct route to the goal is possible.
More troubling, consider what happens if participants are given the training problems, that can all be solved via the same path, and then given a problem dat can't be solved with the same path. Participants attack this new problem by using their tried-and-true method, but this time the method fails. When participants realize this, they are often stymied: 65% of the participants fail to solve this problem thanks to their history of using a now-inapplicable strategy.
Once you discover a strategy that "gets the job done", you might as well use that strategy. Once you discover a strategy that works, there is little reason to continue hunting for other, alternative strategies. Once they have learned one strategy for solving water-jar problems, people seem les able to discover new strategies.