Cultural success of ineffective treatments

Posted on May 6, 2009

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Apart from the work on emulation and imitation mentioned in the previous post, at least two other things from St. Andrews struck me as highly relevant to own research. The first of these was a poster by Tanaka, Kendal and Laland on how non-effective medical treatments might be perpetuated. Since I’ve returned, I’ve had the opportunity to read the actual paper – thanks to Tom Rees who mentions it on his blog I didn’t even have to chase it up. The basic idea is that, under a set of relatively plausible assumption about how treatments come to be adopted by people, it seems that ineffective treatments come to be passed on thanks to their ineffectiveness. The reason is that, being ineffective, they may continue to be used by someone for a longer period of time, making it likelier that someone else will come to notice and adopt the same treatment. A lovely result in that while it is originally counter-intuitive it becomes obvious once understood:

Complementary medicines, traditional remedies and home cures for medical ailments are used extensively world-wide, representing more than US$60 billion sales in the global market. With serious doubts about the efficacy and safety of many treatments, the industry remains steeped in controversy. Little is known about factors affecting the prevalence of efficacious and non-efficacious self-medicative treatments. Here we develop mathematical models which reveal that the most efficacious treatments are not necessarily those most likely to spread. Indeed, purely superstitious remedies, or even maladaptive practices, spread more readily than efficacious treatments under specified circumstances. Low-efficacy practices sometimes spread because their very ineffectiveness results in longer, more salient demonstration and a larger number of converts, which more than compensates for greater rates of abandonment. These models also illuminate a broader range of phenomena, including the spread of innovations, medical treatment of animals, foraging behaviour, and self-medication in non-human primates.

Clearly, the main significance of the paper really is in identifying the kinds of conditions that make the adoption of ineffective treatments more likely. These are recurrent illnesses, that often tend to disappear of their own accord and that are not normally deadly. In other words, just the kinds of colds and other minor ailments that seem to attract the greatest number of quack medicines. While this is an interesting result, there are some problems with it. The first is whether the apparent connection between quack medicine and these ailments is due to the kind of effect Laland and others are considering or, whether, it is simply due to such ailments being very common and, therefore, a large potential market. The second issue is that susceptibility to magical thinking seems to be correlated with particularly dangerous situations and minor ailments do not seem to fit this category as well as, for example, cancer – another category of illness that seems to have a lot of quack treatments connected to it, of course.

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