Chapter 1. Water Jug Problem

1.1 Introduction

Cognitive Tool Kit

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Water Jug Problem

Problem solving is a topic in the higher-level cognitive domain that is of obvious interest to psychologists. Many people think they are fairly adept at cognitive puzzles, but such problems are not always what they seem. This experiment tests your problem solving abilities.

1.2 Experiment Setup

1.3 Instructions

Instructions

Press the space bar to start the experiment. A set of problems will then appear on the screen one at a time, with instructions for each problem regarding how to solve it and enter your answer. After you enter your answer for one problem, press the Enter key. A new screen will be displayed that will prompt you to move on to the next problem. When you have solved all the problems, the experiment will be finished.

1.4 Experiment

Begin Experiment

1.5 Results

Results

1.6 Debriefing

Debriefing

This experiment replicates the work of Luchins (1942). Luchins used his well-known water jug problem as a model for the problem-solving error known as mental set. Mental set is an inhibitory phenomenon that occurs when individuals required to solve a novel problem insistently employ a frequently used strategy that has been successful for them in the solution of other types of problems. The concept of a mental set is similar to the notion of functional fixedness, where a person cannot use an object in novel ways because they are “stuck” using the object for only its intended function. For example, a person sees a screwdriver as only an object for use with screws and not a possible tool to solve the problem of opening a can of paint. Similarly, a mental set is when a person's approach to solving a problem is biased by a previously experienced problem.

In Luchins's water jug problem, participants are required to find the optimal strategy for filling a water jug of a specified volume. They are presented with other jugs of various sizes and must use them to produce the desired volume. Luchins (1942) found that solving the pre-test problems led to a pattern of non-optimal problem-solving that perseverated through the testing. This means that because the pre-test problems required a more complex solution, the participants who were required to solve them got in the habit of solving problems that way and continued this pattern when given easier problems. Luchins (1942) believed this was a phenomenon seen generally in humans—we fall into a pattern of thinking and are resistant to change.

Recent research on transfer of learning during problem solving has demonstrated that when problems are similar on the surface, the mental set problem can be exacerbated.

References:

Luchins, A. S. (1942). Mechanization in problem solving: The effect of Einstellung. Psychological Monographs, 54(6), 3-95.

Wiley, J. (1998). Expertise as mental set: The effects of domain knowledge in creative problem solving. Memory & Cognition, 26(4), 716-730.

Hunter, I. M. (1956). The influence of mental set on problem solving. British Journal of Psychology, 47, 63-64.

1.7 Quiz

Quiz

Question 1.1

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Correct.

Incorrect.

The water jug problem demonstrates that one consequence of having a solution to a problem is that, if well-learned, the solution may prevent us from seeing more efficient solutions to the problem. Luchins (1942) identified a perseveration error in which participants were forced to use a particular strategy for the early examples and then failed to shift to a more efficient strategy for the later examples because they had taken on a “mental set” and continued to solve problems in the manner that was most effective in the early examples.

Question 1.2

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Correct.

Incorrect.

The primary independent variable was whether participants were exposed to the list of complex problems prior to the target problem.

Question 1.3

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Correct.

Incorrect.

The primary dependent variable was the solution used to solve the problem.

Question 1.4

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Correct.

Incorrect.

Luchins studied the higher-level cognitive domain known as problem solving.

Question 1.5

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Correct.

Incorrect.

Mental set occurs when participants attempt to solve a novel problem using a frequently used, but less efficient strategy. Although the strategy has been successful with other types of problems, it is not the most efficient strategy for the target problem.