Memes of Ulcers and Bacteria

From: Keith Henson (
Date: Sun 16 Mar 2003 - 19:07:13 GMT

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    Ulcers and Bacteria I: Discovery and Acceptance* Paul Thagard Philosophy Department University of Waterloo

    In 1983, Dr. J. Robin Warren and Dr. Barry Marshall reported finding a new kind of bacteria in the stomachs of people with gastritis. Warren and Marshall were soon led to the hypothesis that peptic ulcers are generally caused, not by excess acidity or stress, but by a bacterial infection. Initially, this hypothesis was viewed as preposterous, and it is still somewhat controversial. In 1994, however, a U. S. National Institutes of Health Consensus Development Panel concluded that infection appears to play an important contributory role in the pathogenesis of peptic ulcers, and recommended that antibiotics be used in their treatment. Peptic ulcers are common, affecting up to 10% of the population, and evidence has mounted that many ulcers can be cured by eradicating the bacteria responsible for them.

    (large snip to conclusion)

    Initially, Marshall thought that his hypothesis about a bacterial cause for ulcers would gain quick acceptance. Discouraged by the negative reception, he came to believe that only the development of a new generation of gastroenterologists would bring acceptance of the new ideas. This prediction has proven to be unduly pessimistic, even as the early estimate of quick acceptance was unduly optimistic. Increasingly, the view that peptic ulcers are caused by H. pylori is being accepted by medical researchers, although acceptance by practitioners has been much slower. Not surprisingly, the process has been very complex, and a variety of studies have contributed to displaying the greater explanatory coherence of the new theory.

    I have shown how the hypothesis that Helicobacter pylori is the principal cause of peptic ulcers, which was largely rejected as absurd in 1983, could be on the way to medical orthodoxy in 1995. Satisfying Koch's postulates is not a necessary condition of showing that a microorganism causes a disease. Curing the disease by eliminating the microorganism is a powerful manipulation that provides substantial evidence that the microorganism causes the disease, and this kind of intervention has been repeatedly successful in the ulcers/bacteria case. However, accepting the hypothesis that bacteria cause ulcers is not just a matter of appreciating one kind of evidence, but rather of appreciating how the hypothesis coheres with various kinds of evidence and with other hypotheses. For most researchers, the claim that ulcers cause bacteria was not part of the most coherent account in 1983, but it is maximally coherent in 1996.

    Cognitive coherence is, however, only part of the story about why the bacterial theory of ulcers has been increasingly accepted. This paper has treated belief change as a largely psychological phenomenon, a process in the minds of medical researchers. But the development of medical science also requires attention to the interactions of researchers with the world by means of instruments and experiments and the social interactions of researchers with each other and other parts of society (see Thagard, forthcoming-b). A full naturalistic account of the rise of the bacterial theory of ulcers should eventually specify how the cognitive aspects of belief formation and change described in this paper interact with the physical and social aspects of the development of science.

    ***************** (end of quote)

    While not analyzed in memetics terms in this paper, the change in the way peptic ulcers are viewed and treated over the last 20 years certainly makes a very nice example of the spread of a meme from nothing to approaching universal. The previous dominate meme, that ulcers were caused entirely by stress, was largely displaced over that time period. It would have been fascinating to survey researchers and practitioners at intervals to see where support for the previously dominant meme fell below half. This past information might be recoverable from medical journal articles and similar sources over the past two decades, retrospective surveys of gastroenterologists, or patient treatment records (when did a particular doctor in a substantial random sample start treating ulcers with antibiotics?). It is noted in the article that the meme penetrated research and practitioner populations at a different rate.

    The spread of a meme (Bacteria cause most ulcers) displacing a previous one
    (Stress causes ulcers) is a really neat type case. It would not take a lot of work to graph the change over curves for researcher and practitioner populations. (S shaped in both cases I bet.) Since we don't need really high accuracy to resolve the displacement curve, satisfactory research for a paper on this subject could be done for a few hundred dollars or an equivalent amount of time.

    Any takers?

    Keith Henson

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