From The National Library of Medicine via PubMed:
Abstract: The Einstellung (set) effect occurs when the first idea that comes to mind, triggered by familiar features of a problem, prevents a better solution being found. It has been shown to affect both people facing novel problems and experts within their field of expertise. We show that it works by influencing mechanisms that determine what information is attended to. Having found one solution, expert chess players reported that they were looking for a better one. But their eye movements showed that they continued to look at features of the problem related to the solution they had already thought of. The mechanism which allows the first schema activated by familiar aspects of a problem to control the subsequent direction of attention may contribute to a wide range of biases both in everyday and expert thought – from confirmation bias in hypothesis testing to the tendency of scientists to ignore results that do not fit their favoured theories.
Link to the rest at PubMed
Einstellung literally means “setting” or “installation” as well as a person’s “attitude” in German. Related to Einstellung is what is referred to as an Aufgabe (“task” in German). The Aufgabe is the situation which could potentially invoke the Einstellung effect. It is a task which creates a tendency to execute a previously applicable behavior. In the Luchins and Luchins experiment a water jar problem served as the Aufgabe, or task.
The Einstellung effect occurs when a person is presented with a problem or situation that is similar to problems they have worked through in the past. If the solution (or appropriate behavior) to the problem/situation has been the same in each past experience, the person will likely provide that same response, without giving the problem too much thought, even though a more appropriate response might be available. Essentially, the Einstellung effect is one of the human brain’s ways of finding an appropriate solution/behavior as efficiently as possible. The detail is that though finding the solution is efficient, the solution itself is not or might not be.
Another phenomenon similar to Einstellung is functional fixedness (Duncker 1945). Functional fixedness is an impaired ability to discover a new use for an object, owing to the subject’s previous use of the object in a functionally dissimilar context. It can also be deemed a cognitive bias that limits a person to using an object only in the way it is traditionally used. Duncker also pointed out that the phenomenon occurs not only with physical objects, but also with mental objects or concepts (a point which lends itself nicely to the phenomenon of Einstellung effect.
Link to the rest at Wikipedia