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2012 February 27

Scientists don’t test hypotheses

Filed under: Science fair — gasstationwithoutpumps @ 15:33
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On his Computing Education Blog, Mark Guzdial wrote about Nancy Nersessian’s work on how scientists really work: The Scientific Method is wrong: Scientists don’t test hypotheses, but build models.  He describes her idea as

Rather than test hypotheses, scientists do experiments to influence their models of how the world works.  The hypotheses they test come out of those models, …

That is hardly a new idea.  I’ve been trying to convince teachers for years that a hypothesis is not a guess, not even an educated guess, but the prediction of a model in a situation in which different models make different predictions. (See Science fair time again or Google science fair, for example).

I suppose that technically the term “hypothesis” should be used for the model, rather than for the prediction made from the model, because it comes from the Greek ὑπόθεσις (hypóthesis), meaning basis or supposition. But what gets stuck in the “hypothesis” box in science-fair forms is usually the prediction, not the model (if we should be so fortunate as to have a model rather than a wild-ass guess from the students).

Perhaps we should banish the term “hypothesis” from science fairs entirely, since it is used so badly. In its place we should ask students to provide the models that their experiment can distinguish among, and the predictions that would result from each model.  By making the models (always plural!) be the center of attention, rather than the prediction, I think we could correct a lot of the misunderstandings that abound about the scientific method.



  1. Not only is hypothesis used incorrectly, but it’s mostly used synonymously with “question,” whose purpose on the poster is a bit of a mystery to me. Still, I’ve seen model used in myriad ways, too, and I don’t see its substitution for Hypothesis as a panacea. We could discuss “hypothesis” in the context of hypothesis testing.

    Also, not all science includes a model or a hypothesis. I would love to see a bit more honesty about that. Mapping stars, planets, species, and genes are not experimental endeavors, yet collectively they are a central element of science.

    Comment by Jennie Dusheck — 2012 February 29 @ 12:24 | Reply

    • I agree that “discovery science”, where large catalogs of data are acquired in the hopes that interesting things will emerge (like sequencing genomes or doing mRNA expression analyses not knowing what genes will turn out to be interesting), is a major part of science and becoming ever more important. Unfortunately, science-fair judges and NIH panels are strongly biased against that sort of research, and want everything to be “hypothesis-driven” or “model-driven”.

      I’ve often felt that this was a result of physicist envy on the part of the biologists—physics is mainly a model-driven science and biology is mainly a data-driven science. (That is, the physics make up models and then design experiments to test the models—the biologists have much more complex systems and need to collect a lot of data before even over-simplified models can be constructed.)

      The success of physics in the middle of the 20th century led to (a simplified version of) their view of science becoming the canonical view in schools, to the detriment of other sciences.

      Comment by gasstationwithoutpumps — 2012 February 29 @ 14:08 | Reply

      • Hmm. I’m going to quibble. Discovery science, surveys, and mapping have been important for a long time. Think of the geologic mapping done by the US Geological Survey in the 19th century. The theory of evolution could not have come into being without the extensive work of natural historians and biogeographers of the 17th – 19th centuries. And where would Kepler have been without Tycho Brahe’s data? Mapping and surveys have been a part of science since it’s beginnings. Galen and later anatomists mapped the body, work that had to precede Harvey’s model of the circulation.

        I like your formulation of physics being model driven and biology, data driven and that models in biology usually have to explain pretty simple subsystems. Certainly, the emphasis on experiment comes from physics, but I’m not sure I’d characterize it as envy. Many of the early molecular biologists were trained as physicists but couldn’t find work in physics after WW II, and “fled” to biology. They brought an ethos of experiment (a good thing) and a sense that nothing that was done before they came along to fix biology was really any good (a bad thing). In fact, I think it was the intellectual peers and descendants of Watson and Crick who most emphasized the model as a way to understand phenomena. It’s ironic since those two performed no experiments and the data they used to build their model of DNA came from the work of others, e.g., Chargaff and Franklin.

        Comment by Jennie Dusheck — 2012 February 29 @ 16:17 | Reply

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