In problem-solving research, fixation is the inability to see a problem from a fresh perspective. Prior experience or a habitual approach blocks the path to a solution that would otherwise be available.

Functional fixedness is a common form: the tendency to see an object only in terms of its usual function. In the classic candle problem, people struggle to mount a candle on a wall using a box of matches because they see the box only as a container, not as a potential shelf. Mental set is a related form: the tendency to approach a new problem with strategies that worked on similar past problems, even when a simpler approach exists.

Fixation is not stupidity. It is the downside of the same mechanisms that make expert performance efficient. Experts rapidly recognize familiar patterns; the cost is reduced flexibility when the pattern does not apply. Techniques that disrupt fixation include taking a break, considering the opposite, or deliberately generating wild alternatives.

Sometimes the obstacle to solution is not lack of knowledge but the grip of an old way of seeing.