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Fix the Candle


30 minutes

Learning Outcomes

Students will be able to understand some common barriers that prevent people from efficiently solving problems and  they will be able to think of unconventional uses of objects to solve a problem.

Resources & Preparation Needed

  • Small candle per group
  • Box of matches per group
  • Box of thumbtacks per group
  • Surface (cardboard, cork board or wall) where the candle can be fixed 


Divide the class in groups of 4.

Give each group the same task:  test presents the participant with the following task: fix and light a candle on a wall or a cork board in a way so the candle wax won’t drip onto the table/floor below and (obviously) the candle won’t burn the wall/ cardboard.

Give each group the same objects:

  • candle
  • box of matches
  • box of thumbtacks

Ask them to first discuss in the group and agree on a best solution before actually performing it. Thus the groups will not “copy” each others’ solutions. (Best would be if each group could be in separate rooms or other settings applied to prevent the groups from seeing each others’ experiments.)

The “traditional” solution is to empty the box of thumbtacks (or the box of matches if the matches are provided in a box) and use the thumbtacks to nail the box to the wall, put the candle into the box, and light the candle with the match.  Students may explore other creative, but less efficient, methods to achieve the goal (e.g. trying to tack the candle to the wall without using the thumbtack box.)

If you see that some groups have hard time finding the solution, go to that group, empty the box of thumbtacks on their table and ask them to think of using the box as a separate object.

Once most of the groups have found the solution, discuss the experience with the whole group – see assessment questions below.

Source: The “candle problem” or “candle task” was invented by psychologist Karl Duncker’s candle problem, as a cognitive performance test, measuring the influence of functional fixedness (“mental block against using an object in a new way that is required to solve a problem”) on a participant’s problem solving capabilities.

Ideas For Reflection

Once the activity has been completed, discuss with the whole group the experience and what they have learnt from it:

  • How did your group get to the solution, what was the “Aha!” moment?
  • If your group could not solve the problem what was the main block? (mental fixedness)
  • How did you cooperate within the group? What have you learnt from this cooperation process?
  • In small groups again students can think of unusual, abnormal uses of everyday objects (e.g. a brick or a waist belt). This can be organized as a competition among the groups: Which group can think of more uses?
  • How can all this experience help you next time when you meet a problem? How can it help you overcome your mental fixedness?

Extra Material

Video explanations:



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