Chapter 1 What Is Psychology? 17our beliefs into disarray. Critical thinkers are
willing to accept this state of uncertainty. They
are not afraid to say, “I don’t know yet” or “I’m
not sure.”
In science, tolerating uncertainty means that
researchers must avoid drawing firm conclusions
until other researchers have repeated, or replicated,
their studies and verified their findings. Secrecy
is a big no-no in science; you must be willing to
tell others where you got your ideas and how you
tested them so that others can challenge them if
they think your findings are wrong. Replication is
an essential part of the scientific process because
sometimes what seems to be a major discovery
turns out to be only a fluke.
The need to accept a certain amount of un-
certainty does not mean that we must abandon all
assumptions, beliefs, and convictions. That would
be impossible, in any case: We all need values and
principles to guide our actions. The problem is
not that people hold convictions; it is that they
so often refuse to give up convictions that have
proven to be outdated, dangerous, foolish, or sim-
ply wrong.Critical thinking is a tool to guide us on a
lifelong quest for understanding—a tool that we
must keep sharpening. No one ever becomes
a perfect critical thinker, entirely unaffected by
emotional reasoning and wishful thinking. We are
all less open-minded than we think; it is far easier
to poke holes in another person’s argument than
to critically examine our own position. Yet we
think the journey is well worth the mental effort
because the ability to think critically can help you
in countless ways, from saving you money to im-
proving your relationships.
As you read this book, we will give you many
opportunities to apply the eight guidelines to
psychological theories and to personal and social
issues that affect us all. From time to time, a tab
with a light bulb symbol (like the one shown here)
will highlight a discussion where one or more
of our critical-thinking guidelines are especially
relevant. In Quick Quizzes, the light bulb will
identify questions that give you practice in ap-
plying the guidelines yourself. Keep in mind,
however, that criti-
cal thinking is im-
portant throughout
the book, not only
where the light bulb
appears. Finally, at
the end of every chapter, a feature called “Taking
Psychology With You” will help you apply critical
thinking to a topic in the chapter and take its mes-
sage with you.About...not to shut out alternative possibilities. They
generate as many interpretations of the evidence
as they can before choosing the most likely one.
Suppose a news magazine reports that people
who are chronically depressed are more likely
than nondepressed people to develop cancer.
Before concluding that depression causes can-
cer, you would need to consider some other
possibilities. Perhaps depressed people are more
likely to smoke and to drink excessively, and
these unhealthful habits increase their cancer
risk. Or perhaps early, as-yet-undetected cancers
produce biochemical changes that contribute to
the physical and emotional symptoms of depres-
sion. Alternative explanations such as these must
be ruled out by further investigation before we
can conclude that depression is a direct cause of
cancer. (It’s not, by the way.)8
Tolerate Uncertainty. Ultimately, learning to
think critically teaches us one of the hard-
est lessons of life: how to live with uncertainty.
Sometimes there is little or no evidence available
to examine. Sometimes the evidence permits only
tentative conclusions. Sometimes the evidence
seems strong enough to permit strong conclu-
sions until, exasperatingly, new evidence throwsHypnosis has traditionally been considered a trance state
in which people involuntarily do things they ordinarily
could not or would not do. But might there be another
interpretation of the surprising things that hypnotized
people often do? (We will look at competing explanations
in Chapter 5.)Thinking
CriTiCally