Confirmation Bias: A Ubiquitous Phenomenon in Many Guises

210 RAYMOND S. NICKERSON
Confirmation Bias Compounding
Inadequate Search
The idea that inadequate effort is a basic
cause of faulty reasoning is common among
psychologists. Kanouse (1972) suggested that
people may be satisfied to have an explanation
for an event that is sufficient and not feel the
need to seek the best of all possibilities. Nisbett
and Ross (1980) supported the same idea and
suggested that it is especially the case when
attempting to come up with a causal explanation:
The lay scientist seems to search only until a plausible
antecedent is discovered that can be linked to the
outcome through some theory in the repertoire. Given
the richness and diversity of that repertoire, such a
search generally will be concluded quickly and easily.
A kind of vicious cycle results. The subjective ease of
explanation encourages confidence, and confidence
makes the lay scientist stop searching as soon as a
plausible explanation is adduced, so that the complexities
of the task, and the possibilities for "alternative
explanations" no less plausible than the first, are never
allowed to shake the lay scientist's confidence, (p. 119,120)
Perkins and his colleagues expressed essentially
the same idea with their characterization
of people as make-sense epistimologists (Perkins
et al., 1983, 1991). The idea here is that
people think about a situation only to the extent
necessary to make sense—perhaps superficial
sense—of it:
When sense is achieved, there is no need to continue.
Indeed, because further examination of an issue might
produce contrary evidence and diminish or cloud the
sense of one's first pass, there is probably reinforcement
for early closure to reduce the possibility of
cognitive dissonance. Such a makes-sense approach is
quick, easy, and, for many purposes, perfectly adequate.
(Perkins et al., 1991, p. 99)
Baron (1985, 1994) and Pyszczynski and
Greenberg (1987) also emphasized insufficient
search as the primary reason for the premature
drawing of conclusions.
All of these characterizations of the tendency
of people to do a less-than-thorough search
through the possibilities before drawing conclusions
or settling on causal explanations are
consistent with Simon's (1957,1983/1990) view
of humans as satisficers, as opposed to optimizers
or maximizers. The question of interest in
the present context is that of how the criterion
for being satisfied should be set. Given that
search is seldom exhaustive and assuming that,
in many cases, it cannot be, how much should be
enough? How should one decide when to stop?
Without at least tentative answers to these
types of questions, it is difficult to say whether
any particular stopping rule should be considered
rational. Despite this vagueness with
respect to criteria, I believe that the prevailing
opinion among investigators of reasoning is that
people often stop—come to conclusions, adopt
explanations—before they should, which is not
to deny that they may terminate a search more
quickly when time is at a premium and search
longer when accuracy is critical (Kruglanski,
1980; Kruglanski & Ajzen, 1983; Kruglanski &
Freund, 1983). The search seems to be not only
less than extensive but, in many cases, minimal,
stopping at the first plausible endpoint.
If this view is correct, the operation of a
confirmation bias will compound the problem.
Having once arrived at a conclusion, belief, or
point of view, however prematurely, one may
thereafter seek evidence to support that position
and interpret newly acquired information in a
way that is partial to it, thereby strengthening it.
Instead of making an effort to test an initial
hypothesis against whatever counterindicative
evidence might be marshalled against it, one
may selectively focus on what can be said in its
favor. As the evidence favoring the hypothesis
mounts, as it is bound to do if one gives
credence to evidence that is favorable and
ignores or discounts that that is not, one will
become increasingly convinced of the correctness
of the belief one originally formed.
Concluding Comments
We are sometimes admonished to be tolerant
of the beliefs or opinions of others and critical of
our own. Laplace (1814/1956), for example,
gave this eloquent advice:
What indulgence should we not have . . . for opinions
different from ours, when this difference often depends
only upon the various points of view where circumstances
have placed us! Let us enlighten those whom
we judge insufficiently instructed; but first let us
examine critically our own opinions and weigh with
impartiality their respective probabilities, (p. 1328)
But can we assess the merits of our own
opinions impartially? Is it possible to put a
belief that one holds in the balance with an
opposing belief that one does not hold and give
them a fair weighing? I doubt that it is. But that