There are two strings hanging from the ceiling that are sufficiently far apart so that a subject can't hold onto both at the same time. Chairs and pliers are available to the subject.

The two string problem

The candle problem presents participants with a set of items, typically a candle, a book of matches, and a box of thumbtacks. The objective is to affix the candle to a wall in such a way that it will not drip wax onto the floor or table below.

The Candle Problem Setup

Duncker's candle problem is a classic experiment used to demonstrate functional fixedness. In this task, participants receive a candle, a book of matches, and a box of thumbtacks, and are asked to attach the candle to a wall without allowing wax to drip onto the floor. To solve the problem, one must overcome the tendency to view the box solely as a container for thumbtacks, and instead empty it, tack it to the wall to serve as a shelf, and stand the candle inside.

Duncker's Candle Problem Experiment (1945)

Fixation on a familiar function of an object. It can prevent people from finding a solution. The candle problem and two string problem are canonical examples.

University of Michigan - Ann Arbor

People have a tendency to focus in on a specific part of a problem which can prevent them from solving that problem.

Fixation

Goldstein, E. B. (2014). Cognitive psychology: Connecting mind, research and everyday experience. Nelson Education.


Cognitive psychology: Connecting mind, research and everyday experience

What Gestalt psychologists call the reforming/reframing of a problem to help find a solution. This is useful to overcome fixation and generate insight.

Restructuring

Functional fixedness

Functional fixedness is a cognitive bias and a specific type of mental set that restricts a person to using an object only in its traditional manner. This fixation on an object's conventional function can impede problem-solving by obscuring novel uses. Research has shown that functional fixedness is a cross-cultural phenomenon, experienced by individuals in both industrialized and non-industrialized societies.

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