Pathological science is an area of research where "people are tricked into false results ... by subjective effects, wishful thinking or threshold interactions." The term was first used by Irving Langmuir, Nobel Prize–winning chemist, during a 1953 colloquium at the Knolls Research Laboratory. Langmuir said a pathological science is an area of research that simply will not "go away"—long after it was given up on as "false" by the majority of scientists in the field. He called pathological science "the science of things that aren't so."
Bart Simon lists it among practices pretending to be science: "categories ... such as ... pseudoscience, amateur science, deviant or fraudulent science, bad science, junk science, and popular science ... pathological science, cargo-cult science, and voodoo science." Examples of pathological science include Martian canals, N-rays, polywater, and cold fusion. The theories and conclusions behind all of these examples are currently rejected or disregarded by the majority of scientists.
Pathological science, as defined by Langmuir, is a psychological process in which a scientist, originally conforming to the scientific method, unconsciously veers from that method, and begins a pathological process of wishful data interpretation (see the observer-expectancy effect and cognitive bias). Some characteristics of pathological science are:
Langmuir never intended the term to be rigorously defined; it was simply the title of his talk on some examples of "weird science". As with any attempt to define the scientific endeavor, examples and counterexamples can always be found.
In 1903, Prosper-René Blondlot was working on X-rays (as were many physicists of the era) and noticed a new visible radiation that could penetrate aluminium. He devised experiments in which a barely visible object was illuminated by these N-rays, and thus became "more visible". Blondlot claimed that N-rays were causing a small visual reaction, too small to be seen under normal illumination, but just visible when most normal light sources were removed and the target was just barely visible to begin with.
N-rays became the topic of some debate within the science community. After a time, physicist Robert W. Wood decided to visit Blondlot's lab, which had moved on to the physical characterization of N-rays. An experiment passed the rays from a 2 mm slit through an aluminum prism, from which he was measuring the index of refraction to a precision that required measurements accurate to within 0.01 mm. Wood asked how it was possible that he could measure something to 0.01 mm from a 2 mm source, a physical impossibility in the propagation of any kind of wave. Blondlot replied, "That's one of the fascinating things about the N-rays. They don't follow the ordinary laws of science that you ordinarily think of." Wood then asked to see the experiments being run as usual, which took place in a room required to be very dark so the target was barely visible. Blondlot repeated his most recent experiments and got the same results—despite the fact that Wood had reached over and covertly sabotaged the N-ray apparatus by removing the prism.
Langmuir offered additional examples of what he regarded as pathological science in his original speech:
A 1985 version of Langmuir's speech offered more examples, although at least one of these (polywater) occurred entirely after Langmuir's death in 1957:
Since Langmuir's original talk, a number of newer examples of what appear to be pathological science have appeared. Denis Rousseau, one of the main debunkers of polywater, gave an update of Langmuir in 1992, and he specifically cited as examples the cases of polywater, Fleischmann's cold fusion and Jacques Benveniste's "infinite dilution".
Polywater was a form of water which appeared to have a much higher boiling point and much lower freezing point than normal water. During the 1960s, many articles were published on the subject, and research on polywater was done around the world with mixed results. Eventually it was determined that many of the properties of polywater could be explained by biological contamination. When more rigorous cleaning of glassware and experimental controls were introduced, polywater could no longer be produced. It took several years for the concept of polywater to die in spite of the later negative results.
In 1989, Martin Fleischmann and Stanley Pons announced the discovery of a simple and cheap procedure to obtain room-temperature nuclear fusion. Although there were many instances where successful results were reported they lacked consistency and hence cold fusion came to be considered to be an example of pathological science. Two panels convened by the US Department of Energy, one in 1989 and a second in 2004, did not recommend a dedicated federal program for cold fusion research. A small number of researchers continue working on the field.
Jacques Benveniste was a French immunologist who in 1988 published a paper in the prestigious scientific journal Nature describing the action of very high dilutions of anti-IgE antibody on the degranulation of human basophils, findings which seemed to support the concept of homeopathy. Biologists were puzzled by Benveniste's results, as only molecules of water, and no molecules of the original antibody, remained in these high dilutions. Benveniste concluded that the configuration of molecules in water was biologically active. Subsequent investigations have not supported Benveniste's findings.
After spending three hours or more in witnessing various experiments, I am not only unable to report a single observation which appeared to indicate the existence of the rays, but left with a very firm conviction that the few experimenters who have obtained positive results, have been in some way deluded. A somewhat detailed report of the experiments which were shown to me, together with my own observations, may be of interest to the many physicists who have spent days and weeks in fruitless efforts to repeat the remarkable experiments which have been described in the scientific journals of the past year.
Dozens of papers were published on this effect, including a number of studies arguing that it was spurious. These days the Allison effect is often featured in accounts of pathological science, alongside the claims for N-rays and cold fusion
Classic cases of pathological science, such as the alleged "discovery" of canals on Mars, N-rays, polywater, cold fusion, and so on are all testament to the fact that dozens of papers can appear in the scientific literature attesting to the reality of the phenomena, which turn out to be entirely illusory.
So there matters stand: no cold fusion researcher has been able to dispel the stigma of 'pathological science' by rigorously and reproducibly demonstrating effects sufficiently large to exclude the possibility of error (for example, by constructing a working power generator), nor does it seem possible to conclude unequivocally that all the apparently anomalous behavior can be attributed to error.