Tuesday, March 22, 2011

Why Scientists Are Never Certain

Scientifically-proven is an oxymoron. In most scientific fields, it is impossible to prove something, e.g., that all birds fly.  We might survey a thousand species throughout the temperate zone and conclude that, yes, all birds fly.  Unless we’ve examined every bird that exists in the world, we cannot say that we’ve proven anything.  Instead, we proceed by trying to falsify a scientific hypothesis. This approach encourages scientists to design rigorous experiments. We search for environments in which birds might not fly and soon discover penguins, ostriches, and other flightless birds. So we amend our hypothesis that “all birds fly” to “most birds fly”.  The discovery of flightless birds raises further questions about bird evolution and adaptation to certain habitats.  Other hypotheses are less easily falsified.  Complex systems, such as ecosystems, and their workings are more challenging. We chip away, a few data points at a time. Sometimes a pattern emerges, which may become the basis of a generalization.

We never stop trying to disprove even widely-accepted concepts. Scientists attempt to replicate previous findings, and in the process sometimes overturn the original result or uncover new information, which adds to the overall picture.  In the process, we continually gain new knowledge, which allows us to modify our initial conceptual model. If instead, we announce that something is finally proven and that we are certain, knowledge stops accumulating. Scientists know that their knowledge about a certain topic is limited and that there are many unknowns yet to be revealed.

The average person rarely understands these concepts and is frustrated when scientists don't express certainty about a subject and equivocate in their answers to questions.  They assume that the scientist, who does not convey certainty about a topic, simply does not know or is confused, is not competent, and/or lacks confidence in their knowledge.  However, the good scientist is prepared to shift her viewpoint when new evidence is unveiled.  This flexibility does not necessarily mean that what scientists thought before was incorrect.  It means that what was previously correct, given the state of knowledge at the time, may be modified in the future with new data.

Scientists state their level of certainty based on statistical probabilities.  We are 95% certain that an observed phenomenon is caused by human activity.  There's a 5% chance that our observation is due to some other process. The average person interprets the lack of absolute, 100% certainty as a weakness...as evidence that scientists don't really know the cause of a particular phenomenon.  However, what if an average person was told that without surgery to remove a malignant brain tumor, there is a 95% chance they would be dead in 6 weeks.  Would a person gamble on the probability that there is a 5% chance that they won’t die and refuse surgery?  I doubt it. 

Such confusion by the public is often exploited by certain interest groups. 

The book, “The Merchants of Doubt” describes how special-interest groups raise doubts in the public’s mind about climate change by highlighting disagreements among scientists about specific points, the lack of complete data on a specific topic, or changes over time in what scientists accept as a valid explanation for some phenomenon. Interestingly, the authors document that the people (some are former scientists) who are behind the climate denial machine are the same people who worked for the tobacco industry (smoking is not harmful) and who were behind the denial of the existence of the ozone hole as well as acid rain. Their basic approach is to plant the idea that there are data on both sides of the issue (neglecting to mention that one side has failed to publish their research in refereed journals and/or was funded by the very industry being investigated).  This strategy creates confusion over issues by a public that is scientifically illiterate. 

When scientists remain silent in response to unscientific claims by doubt-mongers, the public may conclude that the non-scientific viewpoint is correct.  Or worse, that the scientific community is perpetrating a hoax on the public. It’s difficult to convince scientists to speak out—for various reasons, not the least of which is the possibility of becoming a target.

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