Confirmation Bias: A Ubiquitous Phenomenon in Many Guises

204 RAYMOND S. NICKERSON
making of a choice with an outcome that really
matters to the one making it, some ways of
being wrong are likely to be more regretable
than others. Investigators have noted that this
fact makes certain types of biases functional in
specific situations (Cosmides, 1989; Friedrich,
1993; Hogarth, 1981; Schwartz, 1982). When,
for example, the undesirable consequences of
judging a true hypothesis to be false are greater
than those of judging a false hypothesis to be
true, a bias toward confirmation is dictated by
some normative models of reasoning and by
common sense.
Friedrich (1993) argued that "our inference
processes are first and foremost pragmatic,
survival mechanisms and only secondarily truth
detection strategies" (p. 298). In this view,
peoples' inferential strategies are well suited to
the identification of potential rewards and the
avoidance of costly errors, but not to the
objective of hypothesis testing in accordance
with the logic of science. Inference strategies
that are often considered to be seriously flawed
not only may have desired effects in real-world
contexts, but may also be seen as correct when
judged in terms of an appropriate standard.
To illustrate the point, Friedrich (1993) used
the example of an employer who wants to test
the hunch that extroverts make the best salespeople.
If the employer checked the sales
performance only of extroverts, found it to be
very good and, on this basis, decided to hire only
extroverts for sales positions, one would say that
she had not made an adequate test of her hunch
because she did not rule out the possibility that
introverts might do well at sales also. But if her
main objective was to avoid hiring people who
will turn out to be poor at sales, satisfying
herself that extroverts make good sales people
suffices; the fact that she has not discovered that
introverts can be good at sales too could mean
that she will miss some opportunities by not
hiring them, but it does not invalidate the
decision to hire extroverts if the objective is to
ensure that poor performers do not get hired.
Schwartz (1982) also argued that when
responses have consequences that really matter,
people are more likely to be concerned about
producing desirable outcomes than about determining
the truth or falsity of hypotheses.
Contingent reinforcement may create functional
behavioral units that people tend to repeat
because the behaviors have worked in the past,
and a bias toward confirmation is one of the
stereotyped forms of behavior in which the
operation of these units manifests itself. In
performing a rule-discovery task, one may be
attempting to maximize the probability of
getting a positive response, which is tantamount
to seeking a rule that is sufficient but not
necessary to do so. Given that one has identified
a condition that is sufficient for producing
desired outcomes, there may be no compelling
reason to attempt to determine whether that
condition is also necessary. Schwartz pointed
out too that, especially in social situations such
as some of those studied by Snyder and
colleagues attempting to evaluate hypotheses by
falsification would require manipulating people
and could involve considerable social cost.
Baron (1994) noted that truth seeking or
hypothesis testing often may be combined with
one or more other goals, and that one's behavior
then also must be interpreted in the light of the
other goal(s). If, for example, one is curious as
to why a cake turned out well despite the fact
that certain ingredients were substituted for
those called for by the recipe, one may be
motivated to explore the effects of the substitutions
in such a way that the next experimental
cake is likely to turn out well too.
When using a truth-seeking strategy would
require taking a perceived risk, survival is likely
to take precedence over truth finding, and it is
hard to argue that rationality would dictate
otherwise. It would seem odd to consider
irrational the refusal, say, to eat mushrooms that
one suspected of being poison because the
decision is calculated to preserve one's wellbeing
rather than to shed light on the question of
whether the suspicion is indeed true. In general,
the objective of avoiding disastrous errors may
be more conducive to survival than is that of
truth determination.
The desire to avoid a specific type of error
may coincidentally dictate the same behavior as
would the intention to determine the truth or
falsity of a hypothesis. When this is the case, the
behavior itself does not reveal whether the
individual's intention is to avoid the error or to
test the hypothesis. Friedrich (1993) suggested
that some behavior that has been taken as
evidence of people's preference for normative
diagnostic tests of hypotheses and their interest
in accuracy could have been motivated instead
by the desire to avoid specific types of errors. In