Confirmation Bias: A Ubiquitous Phenomenon in Many Guises

208 RAYMOND S. NICKERSON
that the situation was not quite as simple as
some accounts that focus on the closedmindedness
of the geologists at the time would
lead one to believe. The idea of continental drift
was not entirely new with Wegener, for
example, although Wegener was the first to
propose a well-developed theory. A serious
limitation of the theory was its failure to identify
a force of sufficient magnitude to account for the
hypothesized movement of continents. (The
notion of plate tectonics and evidence regarding
sea-floor spreading came much later; LeGrand,
1988.)
Solomon (1992) argued that it was, in part,
because Wegener was not trained as a geologist
and therefore not steeped in the "stabilist"
theories of the time, that his thinking, relatively
unconstrained by prior beliefs about the stability
of continents, could easily embrace a possibility
that was so contrary to the prevailing view. She
pointed out too that when geologists began to
accept the notion of drift, as evidence favoring it
accumulated, it was those with low publication
rates who were the most likely to do so: "their
beliefs were less entrenched (cognitively speaking)
than those who had reasoned more and
produced more, so belief perseverance was less
of an impediment to acceptance of drift" (p. 449).
Although Solomon (1992) argued that bias
and belief perseverance were responsible for
much of the distribution of research effort that
led finally to the general acceptance of the
theory of continental drift, and to that of plate
tectonics to which it led in turn, she does not
claim that a productive distribution could not
have been effected without the operation of
these factors. The question of whether these
factors facilitated or impeded progress in
geology remains an unanswered one; it is not
inconceivable that progress could have been
faster if the distribution of effort were determined
on some other basis.
In any case, it can be argued that a certain
degree of conservativism serves a useful stabilizing
role in science and is consistent with, if not
dictated by, the importance science attaches to
testability and empirical validation. Moreover, if
Ziman (1978) is right, the vast majority of the
new hypotheses put forward by scientists prove
to be wrong:
Even in physics, there is no infallible procedure for
generating reliable knowledge. The calm order and
perfection of well-established theories, accredited by
innumerable items of evidence from a thousand
different hands, eyes and brains, is not characteristic of
the front-line of research, where controversy, conjecture,
contradiction and confusion are rife. The physics
of undergraduate test-books is 90% true; the contents of
the primary research journals of physics is 90% false,
(p. 40)
"According to temperament," Ziman noted,
"one may be impressed by the coherence of
well-established theories, or horrified by the
contradictions of knowledge in the making" (p.
100).
Fischhoff and Beyth-Marom (1983) made a
related point when commenting on Mahoney's
(1977) finding that scientists tended to be less
critical of a fictitious study that reported results
supportive of the dominant hypothesis in their
field than of one that reported results that were
inconsistent with it. They noted that a reluctance
by scientists to relinquish pet beliefs is only one
interpretation that could be put on the finding.
Another possibility is that what appears to be
biased behavior reflects "a belief that investigators
who report disconfirming results tend to use
inferior research methods (e.g., small samples
leading to more spurious results), to commit
common mistakes in experimental design, or,
simply, to be charlatans" (Fischoff and Beyth-
Marom, 1983, p. 251). To the extent that such a
belief is accurate, a bias against the ready
acceptance of results that are disconfirming of
prevailing hypotheses can be seen as a safeguard
against precipitous changes of view that may
prove to be unjustified. It does not follow, of
course, that this is the only reason for a
confirmation bias in science or the only effect.
Is Belief Perseverance Always Bad?
It is easy to see both how the confirmation
bias helps preserve existing beliefs, whether true
or false, and how the perseverance of unjustified
beliefs can cause serious problems. Is there
anything favorable to be said about a bias that
tends to perpetuate beliefs independently of
their factuality? Perhaps, at least from the
narrow perspective of an individual's mental
health. It may help, for example, to protect one's
ego by making one's favored beliefs less
vulnerable than they otherwise would be.
Indeed, it seems likely that a major reason why
the confirmation bias is so ubiquitous and so
enduring is its effectiveness in preserving