Book Definition: The tendency to respond to a new problem in the manner used for a previous problem.

In Your Own Words

  • Using problem solving strategies on a problem that you've used on other problems before.
  • A method that you keep using over and over again to solve similar problems because it has worked before.
  • Fixed pattern of thinking that fails to take into consideration new information or perspectives*

*be careful when using a mental set because it can keep someone from seeing new or simpler solutions to the problem at hand*
~functional fixedness is a type of mental set


  • You typically enter a store by pushing a door open. Every time they come to a door after that, you push the door expecting it to open, even though some doors only open by pulling.
  • When someone's car breaks down, they expect that the same thing is wrong with it this time as when it broke down previously.
  • When you wake up late, you assume that it's because your alarm didn't go off because that's what happened last time, when it could have been because you just did not set your alarm in the first place.
  • When you were stressed about how to write a perfect thesis statement for AP World so they use the same thesis statement format from AP Lang.
  • Solving a long division problem the same way you solved other problems and getting them all correct.
  • An architect is asked to draw blueprints for new roadways in a town. Usually, he creates the roadways to go clockwise but that idea will not work for this town. The mental set doesn't allow for the architect to think of a new system.
  • When a child falls and gets a bruise or injures their head and they ask for a band-aid because maybe the last time they hurt themselves they fell and cut themselves and were given a band-aid.
  • You always solve a math equation using the "acb" method, so when you see an equation that can't be solved by it, you don't know what to do.

Additional Resources


  • Mental Set is where you may rely on a less-than-ideal strategy just because its worked in the past. Your mind set on one single way to complete tasks. In the study made by R. Duncan Luce and Patrick Suppes it states representational measurment is an attempt to understand observations that can be usefully recorded in terms of familiar mathematical forms. When any data can be implanted into numerical forms, our own knowledge of how to calculate can become very useful. Representational measurement can as well relate to one another and Scientific forms like Physics and Psychopysics. Pashler, H. (2002). Stevens' Handbook of Experimental Psychology, 4 Volume Set. S. Yantis, D. Medin, R. Gallistel, & J. Wixted (Eds.). Wiley.

Someone should look into this one...
McGraw, K. O., & McCullers, J. C. (1979). Evidence of a detrimental effect of extrinsic incentives on breaking a mental set. Journal of Experimental Social Psychology, 15(3), 285-294.