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Anecdotes and Animal Models

Steven Novella, MD has published a very good essay titled The Context of Anecdotes and Anomalies. The title is self-explanatory. I encourage all to read it. The essay encompasses two of my favorite topics, postmodernisms and the philosophy of science.

I would add the following to the concepts Dr Novella explains so well.

As readers of this blog know, animal models cannot predict human response to drugs and disease. (See previous blogs, Animal Models in Light of Evolution, and FAQs About the Use of Animals in Science: A handbook for the scientifically perplexed for more.) But what animals can be used for in biomedical research are heuristic devices; they can stimulate thought and be a source for ideas. Vivisection activists however routinely cite instances where animals were used as heuristics to justify their use as predictive models for human response to drugs and disease. As I have said many times, ideas can come from anywhere (some have come from watching sailboats and dreams). If most of the research funding from NIH goes to animal-based research (Greek and Greek 2010), it should come as no surprise that animal-based research has generated a lot of ideas and that some have resulted in knowledge that advanced medical practice. There is really nothing for the vivisection activist to brag about here. The real question is whether using animal models is a better way to search for new ideas than other heuristics, for example clinical observation, studying human tissues, studying chemistry and physics, and studying human populations.

The ideas that have been generated by studying animals still must be tested in humans. Shanks and I go to great lengths to explain this in Animal Models in Light of Evolution. The idea or hypothesis that perturbation of complex system A will result in the same outcome in complex system B cannot be assumed but must be tested. In the case of animal models, most of these ideas turn out to be wrong. There is nothing scientifically wrong with this in and of itself. Most ideas in science turn out to be wrong. But there is something wrong with selling to society the notion that a scientific method is predictive when it is in fact merely a heuristic and, as such, has all the disadvantages associated with any heuristic device.

Anecdotes have historically been a good way for stimulating thought, as have other heuristics, and those thoughts were then tested or studied and scientific and or medical progress was sometimes made. The first time a physician saw a child with birth defects whose mother was prescribed thalidomide, it was an anecdote. The second time he saw such a case, he developed a testable hypothesis: thalidomide is causing this. Other physicians were notified and clinical observation and epidemiology linked thalidomide to phocomelia as well as other birth defects. Anecdotes and animal studies both allow scientists to pose questions that can be turned into hypotheses and be tested. This is science. But no one argues that anecdotes are predictive for human response to drugs and disease. Further, no one should argue that anecdotes or the results from animal models negate the need for the follow-up studies. In medical science, human results rule.

Dr Novella does a much better job of explaining the above difference between the context of discovery and the context of justification and I again refer you to his blog.

Along the same lines, anecdotes should not be used to justify a practice or research method per se. Animal models have given results that matched human results. Animal models have also given results that were exactly opposite human results. When judging the paradigm of using animals to predict human response, these anecdotes are not that valuable. (I say not that valuable as it only takes a few instances of not matching human responses for a practice to have a low positive predictive value or negative predictive value and thus be judged not predictive. While many instances of correlation do not guarantee the system or technique is predictive.)

The vivisection activist at this point will seek to confuse the issue by saying:

1. Animals and humans have a lot in common;

2. That past discoveries have been initiated by using animals; and

3. That animals really do predict human response.

All of which is either wrong or irrelevant. Unless one is willing to say astrology and fortune telling are predictive systems then animal models cannot be said to predict human response to drugs and disease. The fact that animals and humans have things in common and the fact that past discoveries have been initiated by using animals as heuristic devices is not in dispute. But those facts prove nothing in relation to the predictive value of animal models. The argument above, where it is correct, is a non sequitur.

Moreover, changing the subject from prediction to useful or heuristic is also fallacious. If the vivisection activist wants to counter my arguments, he must address my arguments, not set up a straw man or start an entirely new conversation. I have addressed the prediction argument many times (including in the Philosophy, Ethics, and Humanities in Medicine article Are animal models predictive for humans? and have addressed whether society as a whole values the knowledge gained from using sentient animals as heuristics over the sentient animals in the article Is the use of sentient animals in basic research justifiable? (Also in PEHM.) I have made very clear the differences between the two arguments. The vivisection activists, on the other hand, seek to obfuscate. This alone should be informative to the reader.

Evolution, evo devo, genetics, and a study of complex systems places the empirical evidence showing low PPVs and NPVs for animal models in context. And, for that matter, values like PPV and NPV are not anecdotal. Citing examples, cherry picking actually, where animal and human data correlated is anecdotal.

I especially encourage all animal activists that are interested in or campaign against viv to read Dr Novella’s essay. The entire Science-Based Medicine site is a good source for tools that can be used to promote good science as opposed to the nonsense most vivisection activists spout. If you are not reading it, you must know more than me because I read it everyday.

The above should be interpreted for exactly what it says and not confused with what it does not say. Dr Novella’s position on using animals in science may not align with mine.  But his essay has merit regardless.


Greek, R., and J. Greek. 2010. Is the use of sentient animals in basic research justifiable? Philos Ethics Humanit Med 5:14.


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