Solving Problems and
Like any goal-directed activity, thinking can be done well or badly. Thinking that is done well is thinking
of the sort that achieves its goals.
—J. Baron (2000)
Complicated problem-solving and decision-making processes are engaged for all sorts of human
activities. You must make decisions about things as simple as what clothes to put on in the morning
and as complex as how to raise your children. Your decisions can have long-lasting consequences.
The CEO of a company co uld decide to expand based on an overestimate of the company’s ﬁnancial
strength, which may result in bankruptcy. This in turn would result in the loss of many jobs and
have devastating consequences on the local economy. Similarly, a government’s decision to enter
into war will result in loss of life, economic hardship, and aftereffects of varying types that carry far
into the future. Scientists have tried to understand how human reasoning and decision making take
place so that poor decisions can be prevented.
Consider the operator of a human–machine system. To operate the system effectively, he or she
must comprehend system information and decide on appropriate actions. There are two ways that
the operator can control the system (Torenvliet & Vicente, 2006). The ﬁrst mode of operation will
be used when the system is operating in a familiar and predictable way. Under these circumstances,
the operator can contr ol the system with very little effort, relying on well-practiced responses to the
system’s behavior (skill-based performance; see Chapter 3). The operator will face difﬁculty when
system information indicates that an unusual condition has developed, requiring that the operator
change to the second mode of operation. In this mode, the operator will need to make decisions
based on his reasoning about the system state. This reasoning may involve recall of information
from sema ntic or episodic memory (rule-based performance), or formulating a novel solution by
integrating several different sources of information (knowledge-based performance).
For example, most of a pilot’s efforts in ﬂying an airplane involve monitoring the instruments in
the cockpit. This does not require a great deal of mental effort. Only when the instruments indicate
that a problem has occurred must the pilot engage in any effortful problem solving or decision
making. When the pilot determines that an emergency has occurred, he or she must integrate
information from the many visual and auditory displays in the cockpit, diagnose the nature of the
emergency, and decide on the actions he or she should take in response. Yet, as we have discussed
in the previous chapters, the pilot’s capacity for processing such information is limited, and he or she
may make a bad decision even though he or she is well-trained and well-intentioned.
This chapter examines how people reason about and choose between different actions. There are
two ways to describe how people make decisions: normative an d descriptive. A normative model
speciﬁes those choices that a rational person should make under ideal circumstances. However, as
Johnson-Laird (1983, p. 133) observed, ‘‘Human reasoners often fail to be rational. Their limited
Proctor/Human Factors in Simple and Complex Systems ER411X_C011 Final Proof page 289 27.2.2008 3:38pm Compositor Name: BSuresh