Wednesday, April 20, 2011

Should people believe what scientists say?

When a scientist reports an observation, other scientists do not simply accept the observation, but seek to replicate it. It is only when an observation has been independently replicated in several different laboratories by several different scientists that it becomes generally accepted. Even then scientists would be very interested to find circumstances in which a widely replicated observation can not be replicated. So the more widely replicated an observation has been the more confidence you can have in its report.

We hear that autism rates are increasing. That is based on the observation of people exhibiting behavioral syndromes. However, it is also dependent on the syndromes being classified as autism. Now people with more groups of symptoms are classified as autistic than in the past. Taxonomy, the science of classification, is a critical part of science and scientists debate in depth about the right classes to use and the right criteria for inclusion of something in a class. In some areas, such as the classification of common plants and animals, taxonomy is well established and you can have great confidence in such classifications. In other areas, such as genetically distinct species that have converged to be physically extremely similar, the classifications can be less credible.

Similarly, scientists give more credence to theories that have survived many different tests. Still, Newtonian physics which had survived huge numbers of tests over centuries was replaced by Einsteinian physics when it proved better to explain the path of light from distant stars passing close to our sun. Newtonian physics may suffice for 99.99.....% of our experience, but a better theory accounts for still more. Some areas of science have very well supported theories and others not so much.

When scientists are speaking of their own area of scientific training, they speak from years of specialized education and research, and are generally pretty credible. On the other hand, in scientific peer review good practice is to seek opinions from several fully qualified scientists with comparable areas of interest to that being reviewed rather than to simply believe the first opinion one gets. Where one gets different opinions, one seeks more reviews.

When scientists are speaking outside their area of expertise, they are no more credible than others of the same intelligence and general education.

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