238 Chapter 7 Thinking and Intelligence
Some behavioral economists are using MRI
scans to examine brain activity when people play
variations of the Ultimatum Game (Camerer,
2003; Sanfey et al., 2003). While a person is
deciding whether to accept a low offer, two
brain areas are active: a part of the prefron-
tal cortex linked to rational problem solving
and an area that is associated with disgust and
other unpleasant feelings. According to econo-
mist Colin Camerer, “Basically the brain toggles
between ‘Yes, money is good’ and ‘Ugh, this guy
is treating me like crap’” (quoted in D’Antonio,
2004). Some people choose the money and others
go for respect. Which choice do you think you
would make?The Hindsight Bias
There is a reason for the saying that hindsight
is 20/20. When people learn the outcome of an
event or the answer to a question, they are often
sure that they “knew it all along.” Armed with the
wisdom of hindsight, they see the outcome that
actually occurred as inevitable, and they overes-
timate their ability to have predicted what hap-
pened beforehand (Fischhoff, 1975; Hawkins &
Hastie, 1990). This hindsight bias shows up all
the time in evaluating relationships (“I always
knew their marriage wouldn’t last”), politics (“I
could have told you that candidate would win”),
and military opinions (“The generals should have
known the other side would attack”).
According to Scott Hawkins and Reid Hastie
(1990), “Hindsight biases represent the dark side
of successful learning and judgment.” They are
the dark side because when we are sure that wehindsight bias The
tendency to overestimate
one’s ability to have
predicted an event once
the outcome is known;
the “I knew it all along”
phenomenon.
knew something all along, we are also less willing
to find out what we need to know to make
accurate predictions in the future. For example,
in medical conferences, when doctors are told
what the postmortem findings were for a patient
who died, they tend to think the case was easier
to diagnose than it actually was (“I would have
known it was a brain tumor”), and so they learn
less from the case than they should (Dawson
et al., 1988).
Perhaps you feel that we are not telling you
anything new because you have always known
about the hindsight bias. But you may just have a
hindsight bias about the hindsight bias.The Confirmation Bias
When people want to make the most accurate
judgment possible, they usually try to consider
all of the relevant information. But as we saw in
Chapter 1, when they are thinking about an issue
they feel strongly about, they often succumb to
the confirmation bias, paying attention only to evi-
dence that confirms their belief and finding fault
with evidence or arguments that point in a differ-
ent direction (Edwards & Smith, 1996; Nickerson,
1998). You rarely hear someone say, “Oh, thank
you for explaining to me why my lifelong philoso-
phy of child rearing (or politics, or investing, or
dieting) is wrong. I’m so grateful for the facts!”
The person is more likely to say, “Get lost, and
take your crazy ideas with you.”
Once you start looking for it, you will see
the confirmation bias everywhere. Politicians
brag about economic reports that confirm their
party’s position and dismiss counterevidence asconfirmation bias The
tendency to look for or
pay attention only to
information that confirms
one’s own belief.
Get Involved! Confirming the Confirmation Bias
Suppose someone deals out four cards, each
with a letter on one side and a number on the
other. You can see only one side of each card:
Your task is to find out whether the following
rule is true: “If a card has a vowel on one side, then
it has an even number on the other side.” Which
two cards do you need to turn over to find out?
The vast majority of people say they would turn over the E and the 6, but they are wrong. You do need
to turn over the E (a vowel), because if the number on the other side is even, it confirms the rule, and if it is
odd, the rule is false. However, the card with the 6 tells you nothing. The rule does not say that a card with
an even number must always have a vowel on the other side. Therefore, it doesn’t matter whether the 6
has a vowel or a consonant on the other side. The card you do need to turn over is the 7, because if it has
a vowel on the other side, that fact disconfirms the rule.
People do poorly on this problem because they are biased to look for confirming evidence and to
ignore the possibility of disconfirming evidence. Don’t feel too bad if you missed it. Most judges, lawyers,
and people with Ph.D.s do, too.E J (^67)