Today we will learn about the concept of mental set. “Mental set is the tendency to solve certain problems in a fixed way.” Mental set is important in understanding insight (Ah ha! moments), the act of overcoming an impasse that previously stopped progress on a creative problem.
Mental Set & the Water Jug Problem
The effects of mental set were tested using water jug problems where participants had to measure a particular amount of water by pouring amongst the jugs. For example, in one set of problems (set Red) three water jugs A, B, and C are given, each with respective capacities of 21 (A), 127 (B), and 3 (C). The goal is to measure 100 into one of the jugs. One way of solving the problem (measuring 100) would be to fill B up with water, and then from B fill C up twice. And then with what is left of B (now 121) fill up A. Examiners create many sets of problems that follow this exact same solution method (B-2C-A). However, an alternative set (Set Blue) can be solved using a much simpler method. For example, take the problem 23 (A), 49 (B), 3 (C) with a goal of measuring 20. This problem could similarly be solved using the B-2C-A method, however, a much simpler solution is to fill A with water and then empty it out in C (A-C).
Experimental groups first primed with Set Red questions almost never used the simpler solution when given Set Blue questions. However, the control group only given Set Blue question almost always used the simpler solution. Therefore, the repeated success of the method initially used by the experimental group blinded them to a much simpler solution.
Repeated Successful Attempts Blinds us to Alternative Methods
Mental set stands for the proposition “that the repeated application of successful method makes blind any alternative approach.” Mental set can be conceptualized as a set of “procedures.” These procedures are sets of rules that specify a method to be used when faced with particular problems. The more a procedure is used successfully the stronger the mental set will become consequently increasing the likelihood it will be selected in the future.
Mental sets can lead us into a mental rut. Mental rut describes the inability to “switch from an inappropriate solution to a more productive one.” Prior repeated activation of a successful solution can make it impossible to access information leading to success when a problem is similar to others you have faced but cannot be solved with the same solution. It can also be assumed that repeated failure of high probability procedures will weaken the mental set and allow the possibility for less primed procedures to be selected. However a course of repeated failure could be probatively lengthy.
In the next post we will learn strategies for getting out of mental ruts and solving insight problems. These strategies include incubation (which you remember from an earlier post!), chunk decomposition, and constraint relaxation.
 Michael Ollinger, Gary Jones, and Gunther Knoblich, Investigating the Effect of Mental set on Insight Problem Solving, Experimental Psychology Vol. 55 (2008), 269.
 I often analogize Insight with the character Geordi La Forge (from Star Trek). It’s that moment when you save the day by realizing that if you shift power from the sub-capacitor you can use warp drive without diverting power from the shields., For more discussion on the interplay of Mental Set and Insight see generally Id.
 Id. at 269-70.
 Id. at 270.
 See Ollinger, supra note 1, at 271.