HEURISTICS : GERD GIGERENZER [4.2.03]
At the beginning of the 20th century the father of modern science
fiction, Herbert George Wells, said in his writings on politics,
"If we want to have an educated citizenship in a modern technological
society, we need to teach them three things: reading, writing,
and statistical thinking." At the beginning of the 21st century,
how far have we gotten with this program? In our society, we teach
most citizens reading and writing from the time they are children,
but not statistical thinking. John Alan Paulos has called this
There are many stories documenting this problem. For instance,
there was the weather forecaster who announced on American TV
that if the probability that it will rain on Saturday is 50 percent
and the probability that it will rain on Sunday is 50 percent,
the probability that it will rain over the weekend is 100 percent.
In another recent case reported by New Scientist an inspector
in the Food and Drug Administration visited a restaurant in Salt
Lake City famous for its quiches made from four fresh eggs. She
told the owner that according to FDA research every fourth egg
has salmonella bacteria, so the restaurant should only use three
eggs in a quiche. We can laugh about these examples because we
easily understand the mistakes involved, but there are more serious
issues. When it comes to medical and legal issues, we need exactly
the kind of education that H. G. Wells was asking for, and we
haven't gotten it.
What interests me is the question of how humans learn to live
with uncertainty. Before the scientific revolution determinism
was a strong ideal. Religion brought about a denial of uncertainty,
and many people knew that their kin or their race was exactly
the one that God had favored. They also thought they were entitled
to get rid of competing ideas and the people that propagated them.
How does a society change from this condition into one in which
we understand that there is this fundamental uncertainty? How
do we avoid the illusion of certainty to produce the understanding
that everything, whether it be a medical test or deciding on the
best cure for a particular kind of cancer, has a fundamental element
For instance, I've worked with physicians and physician-patient
associations to try to teach the acceptance of uncertainty and
the reasonable way to deal with it. Take HIV testing as an example.
Brochures published by the Illinois Department of Health say that
testing positive for HIV means that you have the virus. Thus,
if you are an average person who is not in a particular risk group
but test positive for HIV, this might lead you to choose to commit
suicide, or move to California, or do something else quite drastic.
But AIDS information in many countries is running on the illusion
of certainty. The actual situation is rather like this: If you
have about 10,000 people who are in no risk group, one of them
will have the virus, and will test positive with practical certainty.
Among the other 9,999, another one will test positive, but it's
a false positive. In this case we have two who test positive,
although only one of them actually has the virus. Knowing about
these very simple things can prevent serious disasters, of which
there is unfortunately a record.
Still, medical societies, individual doctors, and individual patients
either produce the illusion of certainty or want it. Everyone
knows Benjamin Franklin's adage that there is nothing certain
in this world except death and taxes, but the doctors I interviewed
tell me something different. They say, "If I would tell my patients
what we don't know, they would get very nervous, so it's better
not to tell them." Thus, this is one important area in which there
is a need to get people including individual doctors or
lawyers in court to be mature citizens and to help them
understand and communicate risks.