If, as I argued last week, scientists are just as prone as everybody else to confirmation bias—the tendency to look for evidence to support rather than to test your own ideas—then how is it that science, unlike cults and superstitions, does change its mind and find new things?
The answer was spelled out by the psychologist Raymond Nickerson of Tufts University in a 1998 paper: “It is not so much the critical attitude that individual scientists have taken with respect to their own ideas that has given science the success it has enjoyed…but more the fact that individual scientists have been highly motivated to demonstrate that hypotheses that are held by some other scientist(s) are false.”
Most scientists do not try to disprove their ideas; rivals do it for them. Only when those rivals fail is the theory bombproof. The physicist Robert Millikan (who showed minor confirmation bias in his own work on the charge of the electron by omitting outlying observations that did not fit his hypothesis) devoted more than 10 years to trying to disprove Einstein’s theory that light consists of particles (photons). His failure convinced almost everybody but himself that Einstein was right.
A recent example is the case of malaria and climate. In the early days of global-warming research, scientists argued that warming would worsen malaria by increasing the range of mosquitoes. “Malaria and dengue fever are two of the mosquito-borne diseases most likely to spread dramatically as global temperatures head upward,” said the Harvard Medical School’s Paul Epstein in Scientific American in 2000, in a warning typical of many.