On 18 December 1953 at General Electric's Knolls Atomic Power Laboratory, Nobel Prize winner Irving Langmuir gave a colloquium on a certain type of pitfalls into which scientists may stumble. Langmuir coined the term pathological science to describe a category of questionable scientific experiments:
These are cases where there is no dishonesty involved but where people are tricked into false results by a lack of understanding about what human beings can do to themselves in the way of being led astray by subjective effects, wishful thinking, or threshold interactions.

This concept differs from pseudo-science with respect to the scientific honesty of the work. In pseudo-science, the researcher is aware of the lack of value of the work, and poorly applies the scientific method to fool the audience. In pathological science, the researcher is convinced of the validity of the work but ignores all evidence that may disprove this.

In his (now famous) colloquium, Langmuir describes several examples of pathological science. One experiment in which Langmuir himself was involved to debunk the erroneous results was the Davis and Barnes experiment. Columbia University researchers Bergen Davis and Arthur Barnes believed they were detecting a phenomenon called electron capture by alpha particles in a magnetic field. This was done by counting scintillations on a screen in a darkened room, for several hours straight. Langmuir observed that the researchers were also counting visual hallucinations (a common occurrence under those work conditions), and discarding undesired observations as instrumental errors. Other examples include the discovery of the fictitious N-rays, the equally fictitious Mitogenetic Rays that would allow plants to grow faster, and the discovery of certain peculiar elements and isotopes by the so called Allison Effect.

Although some of the examples that Langmuir described in his 1953 colloquium are unthinkable by today's standards, the scientific community nevertheless remains vulnerable to the dangers of pathological research. For instance, consider the Cold Fusion fiasco from 1989. Although Martin Fleischmann and Stanley Pons unquestionably reported their findings to the press too soon (i.e. before publication in a peer-reviewed journal), they made their claims in good faith.

Langmuir describes several Symptoms of Pathological Science:

  • The maximum effect that is observed is produced by a causative agent of barely detectable intensity, and the magnitude of the effect is substantially independent of the intensity of the cause.
  • The effect is of a magnitude that remains close to the limit of detectability, or many measurements are necessary because of the very low statistical significance of the results.
  • There are claims of great accuracy.
  • Fantastic theories contrary to experience are suggested.
  • Criticisms are met by ad hoc excuses thought up on the spur of the moment.
  • The ratio of supporters to critics rises up to somewhere near 50% and then falls gradually to oblivion.

However, it is not difficult to expand this list with several other symptoms:

  • The results are only obtained under highly specific "special" conditions
  • Special equipment or measurement techniques are involved
  • Experiments that would prove the validity of the results beyond any reasonable doubt are not conducted

Langmuir is most famous for his research in surface chemistry, for which he received the Nobel Prize in Chemistry in 1932 . He also spent many years investigating the topic of pathological science, although he never published any work in this field. His colloquium at the Knolls Atomic Power Laboratory in 1953 is considered to be of great historic value. Unfortunately, the tape recording that was made of this colloquium was lost for several years, until a copy was found at the Library of Congress.

A transcript of the colloquium (highly recommended) can be found in:
Irving Langmuir (transcribed and edited by Robert N. Hall), Physics Today 42: 36-48, October 1989.

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