Duncker's Candle, matches and thumb tacks


There is a classic psychology test, known as Duncker’s candle problem, in which subjects are given a candle, a box of matches and some drawing pins (thumb tacks). The task is to fix a lit candle onto a cork-board on the wall so the candle won’t drip wax onto the table below.

The test is a test of ‘functional fixedness’. While we see the matchbox as a ‘box for the matches’ we fail to see its potential use as a shelf. It is used in many psychology experiments.

Tony McCaffrey of the University of Massachusetts, Amherst, has found a way to use our understanding of functional fixedness to boost problem-solving abilities by two thirds. It is a simple, two-step process:

  1. Break down all of the things you have to hand into their smallest components. If a part can be decomposed further, do so.
  2. Give each component the most generic name you can. If the label implies a specific use or range of uses, look for something more generic.

So, for example, a candle becomes wax & string – note: not wax and wick, because the word ‘wick’ may constrain the contexts in which you can envisage it being used.

McCaffrey calls this the Generic Parts Technique and, in tests, finds that subjects who use it solve 67 per cent more problems than control groups who are not taught the process.
This is not a bad boost in problem-solving performance for such a simple change in how you think. Why not give it a go?


Psychological Science, 23(3) 215–218, (2012)
Innovation Relies on the Obscure: A Key to Overcoming the Classic Problem of Functional Fixedness
Tony McCaffrey


Powerhouse, by Mike clayton


My newest book is Powerhouse.

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