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August 14, 2000


Risk Assessment and Confirmation Bias



With this brief monograph, I would like to propose an analysis of the
nature of the 'debate' over biotechnology, and how the anti-biotech
contingent deals with facts and reasoning. It seems obvious that
using objective facts and standard reasoning has had little effect on
the anti-biotechnology contingent, and explaining why this is so may
illuminate further dialogue.

I would suggest that the the anti-biotechnology contingent has made
the lack of scientific omniscience part of a strongly subjective
standard of risk assessment, and coupled it with a confirmation bias.


To make an effective risk management decision, risk managers and
other stakeholders need to know what potential harm a situation poses
and how great is the likelihood that people or the environment will
be harmed. Gathering and analyzing this information is referred to as
risk assessment. From:

This seems patently reasonable, and it is especially tantalizing
because it appeals to the notion of gathering and analyzing
information. However, there are times when the information to be
gathered’ and analyzed’ simply isn't there in the ideal form. Here
one finds the seeds of dispute.

In a classical case, "[r]isk assessment is performed by considering
intrinsic hazards, the extent of exposure to the hazards, and
information about the relationship between exposures and responses."
Ibid. Accordingly, one takes, for example, the number of passenger
miles traveled in the US annually, compares that to the number of
traffic fatalities, and computes the risk of travel by automobile.

In the case of biotechnology, we have not identified any intrinsic
hazards, and while the extent of exposure can easily be estimated,
there are no 'responses' to exposure. We have no such data to work
with, as no one has fallen ill as a result of consuming foods made
from genetically modified crops. There are no 'odds' available.


Stakeholders’ perception of a risk can vary substantially depending
on such factors as the extent to which they are directly affected,
whether they have voluntarily assumed the risk (as in choosing not to
wear a seatbelt) or had the risk imposed on them (as in exposure to
air pollutants), and whether they are connected with the cause of the
risk. Ibid.

It bears pointing out that, where genetically modified foods are not
labeled as such, consumers cannot be said to have voluntarily assumed
a risk, and therefore might be said to have had the risk imposed on
them, as many claim. Certainly they cannot be connected with the
cause of the risk. In such a situation, the emergence and application
of subjective assessments of risk should not be surprising.


In 'Science and Judgment in Risk Assessment' National Academy Press, (1994)
http://books.nap.edu/books/030904894X/html/160.html, the authors
opine that "The need to confront uncertainty in risk assessment has
changed little since the 1983 NRC report Risk Assessment in the
Federal Government. That report found that: "The dominant analytic
difficulty [in decision-making based on risk assessments] is
pervasive uncertainty.... there is often great uncertainty in
estimates or the types, probability, and magnitude of health effects
associated with a chemical agent of the economic effects of a
proposed regulatory action, and of the extent of current and possible
future human exposures. These problems have no immediate solutions,
given the many gaps in our understanding of the causal mechanisms of
carcinogenesis and other health effects and in our ability to
ascertain the nature or extent of the effects associated with
specific exposures."

Because of this, "Risk assessment can be controversial, reflecting
the important role that both science and judgment play in drawing
conclusions about the likelihood of effects on human health and the
environment. Often, the controversy arises from what we don’t know
and from what risk assessments can't tell us, because our knowledge
of human vulnerability and of environmental impacts is incomplete . .
." From:


Those who persist in evaluating risks subjectively, and are prone to
point out that our knowledge of human vulnerability and of
environmental impacts is incomplete, have quite obviously been
attracted to the anti-biotechnology rhetoric. Their sentiments are
rather neatly expressed by some of them with the phrase: “Absence of
evidence is not evidence of absence,” while others prefer to use
phrases such as 'unknown consequences' or 'possible risks.'

>From what we know of incompleteness and subjective risk assessment,
we can see why these people could feel that they have been made
subject to possible risks. This they often express as 'being guinea

Since the application of biotechnology in food production completely
baffles the odds-based approach to risk assessment, one would assume
that it would be possible to do an alternative 'risk assessment'
based on the science involved, and to demonstrate deductively (rather
than inductively) that the risk of consuming foods made from
genetically modified crops simply is 'nothing to worry about.'

Time and time again, this approach has failed to work, among
consumers and scientists of all kinds. They have subjectively
determined the presence and seriousness of an unknown risk. Why can
they not be persuaded?


Confirmation bias refers to a type of selective thinking whereby one
tends to notice and to look for what confirms one's beliefs, and to
ignore, not look for, or undervalue the relevance of what contradicts
one's beliefs. For example, if one believes that during a full moon
there is an increase in accidents, one will take notice when
accidents occur during a full moon, but be inattentive to the moon
when accidents occur during other times of the month. A tendency to
do this over time unjustifiably strengthens one's belief in the
relationship between the full moon and accidents." From:

If this is true, then we are forced to conclude that prior efforts to
"persuade" the anti-biotech contingent is because they are not used
to thinking "scientifically."

If our beliefs are firmly established upon solid evidence and valid
confirmatory experiments, the tendency to give more attention and
weight to data that fits with our beliefs should not lead us astray
as a rule. Of course, if we become blinded to evidence truly refuting
a favored hypothesis, we have crossed the line from reasonableness to
closed-mindedness. Ibid.

This should not necessarily be taken as a condemnation of the
anti-biotech contingent so much as an acknowledgement of a facet of
human nature. "Numerous studies have demonstrated that people
generally give an excessive amount of value to confirmatory
information, i.e., data which is positive or which supports a
position." Ibid.

Indeed, when people go searching on the Internet for information (as
I have done here) they often display confirmation bias. As reported at
http://hsb.baylor.edu/ramsower/ais.ac.96/papers/ward.htm, there is a
"selective perception’ bias that describes decision makers’
inclinations to search out confirming information and to remember
this information. A decision maker may form a hypothesis and then
gather and interpret information so that the hypothesis is supported.
In addition to selective information retrieval, people may be subject
to the confirmation bias due to failure to use disconfirming
information they do encounter."

The problem may be made worse by the actual structure of the Internet.

The ability of WWW users to follow links that look interesting or
promising may exacerbate the effects of the confirmation bias. * * *
WWW features that enable users to switch quickly to other documents
[hyperlinks] may allow them to find the desired confirming
information while avoiding disconfirming information with less
effort. Ibid. (It bears pointing out that much of the anti-biotech
sentiment not found in newspapers is circulated on the Internet.)

Evidence exists virtually everywhere that we are dealing with a form
of confirmation bias, such as the insistence on the authoritativeness
of Losey's Monarch larvae experiments or Pusztai's rat studies, or
the tryptophan case, or deductions based upon the imputed motives of
corporations or scientists, or the unsullied purity of agricultural
practices in developing countries. These slender scraps are
sufficiently fact-like’ and abundant that a confirmation bias will
almost necessarily result in confirming the existence of risks which
have been subjectively identified and assessed.

If we are, then, truly dealing with confirmation bias in the
anti-biotech movement, what is the likelihood that those who tend to
ignore facts which contradict their position will be convinced by
facts which contradict their position? (The question of whether
attacks on farm-scale field trials in Britain can be viewed as a form
of confirmation bias is by no means simple.)


There are few recommendations for effectively dealing with
confirmation bias, and that may be because "Conceptual knowledge is
neither automatic nor self-evident but exists in a complex,
hierarchical interrelationship among its elements." From:

However, one commentator has suggested that "discussion and debate
provide a useful -- and in some cases practically indispensable --
means of achieving the values of integration and objectivity." Ibid.

As though to echo what is going on in the biotechnology 'debate' the
author notes that integrating knowledge through discussion and debate
"can be a difficult process," since overcoming confirmation bias
requires getting a person to focus only on what is real and
relevant--thereby forcing them to re-integrate the complex,
hierarchical interrelationships of their conceptual world. Ibid.

How this might be accomplished in the context of the biotechnology
'debate' is not immediately apparent, but I would point out that, in
general, it is not always easy to get people to change their mind and
say, in effect, "I was wrong." It is fair to surmise that those
suffering most from confirmation bias will be the least likely to
admit being wrong.


At http://www.riskworld.com/Nreports/1997/risk-rpt/html/epajan3.htm
is found a flow chart which often appears in the literature regarding
risk assessment in a public setting. According to the flow chart, one
is supposed to consider 'options' when a risk is 'identified.'

If this model is not merely ideal, but descriptive of human behavior,
then it shows that many in the anti-biotech contingent are stuck in
the 'options' portion of the risk assessment cycle. Believing they
have identified a risk, they proliferate options to biotechnology,
such as organic farming, or sustainable farming, or a moratorium
pending further testing, or labeling, or outright bans on use of the
technology. This tendency is exacerbated in developed nations, where
abundant food and a strong economy easily makes such options


The anti-biotech side of the biotechnology 'debate,' on this
analysis, has used the incompleteness of the scientific enterprise to
subjectively identify unknown risks which, coupled with a
confirmation bias in favor of proving the existence and seriousness
of the risks, amounts to a roadblock preventing them from absorbing
and processing relevant objective information. If this confirmation
bias is to be overcome, it appears necessary to focus those against
biotechnology on what is relevant to an objective risk assessment
based on scientific reasoning, although it is not clear how this
might be accomplished in practice.

(I would also add that it is entirely possible that this theory not
only explains the precautionary principle, but how it is applied, as