Understanding Psychology (10th Ed)

 
Module 24 
Problem Solving 
259
obstacles to problem solving can exist at each of the three major stages. Although 
cognitive approaches to problem solving suggest that thinking proceeds along fairly 
rational, logical lines as a person confronts a problem and considers various solu-
tions, several factors can hinder the development of creative, appropriate, and accu-
rate solutions.
 FUNCTIONAL FIXEDNESS AND MENTAL SET 
The diffi culty most people experience with the candle problem is caused by  functional 
fi xedness ,
the tendency to think of an object only in terms of its typical use. For instance, 
functional fi xedness probably leads you to think of this book as something to read 
instead of its potential use as a doorstop or as kindling for a fi re. In the candle problem, 
because the objects are fi rst presented inside the boxes, functional fi xedness leads most 
people to see the boxes simply as containers for the objects they hold rather than as a 
potential part of the solution. They cannot envision another function for the boxes.
Functional fi xedness is an example of a broader phenomenon known as  mental set, 
the tendency for old patterns of problem solving to persist. A classic experiment 
(Luchins, 1946) demonstrated this phenomenon. As you can see in Figure 9, the 
object of the task is to use the jars in each row to measure out the designated 
amount of liquid. (Try it yourself to get a sense of the power of mental set before 
moving on.)
If you have tried to solve the problem, you know that the fi rst fi ve rows are all 
solved in the same way: First fi ll the largest jar (B) and then from it fi ll the middle-size 
jar (A) once and the smallest jar (C) two times. What is left in B is the designated 
amount. (Stated as a formula, the designated amount is B–A–2C.) The demonstration 
of mental set comes in the sixth row of the problem, a point at which you probably 
encountered some diffi culty. If you are like most people, you tried the formula and were 
perplexed when it failed. Chances are, in fact, that you missed the simple (but different) 
solution to the problem, which involves merely subtracting C from A. Interestingly, 
people who were given the problem in row 6 fi rst had no diffi culty with it at all.