- Do Pressures to Publish Increase Scientists' Bias? An Empirical Support from US States Data
By Daniele Fanelli
PLoS ONE 5(4): e10271. 1
In a random sample of 1316 papers that declared to have “tested a hypothesis” in all disciplines, outcomes could be significantly predicted by knowing the addresses of the corresponding authors: those based in US states where researchers publish more papers per capita were significantly more likely to report positive results, independently of their discipline, methodology and research expenditure... [T]hese results support the hypothesis that competitive academic environments increase not only the productivity of researchers, but also their bias against “negative” results.
When I read that, I was somewhat surprised about the conclusion. Sure, such a result would "support" the named hypothesis in the sense that it didn't contradict it. But it seems to me like jumping to conclusions. How many other hypothesis can you come up with that are also supported by the results? I'll admit that I hadn't even read the whole paper when I made up the following ones:
- Authors who publish negative results are sad and depressed people and generally less productive.
- A scientist who finds a negative result wants more evidence to convince himself his original hypothesis was wrong, thus the study takes longer and in toto less papers are published.
- Stefan suggested that the folks who published more papers are of the sort who hand out a dozen shallow hypothesis to their students to be tested, and are likely to be confirmed. (Stefan used the, unfortunately untranslatable, German expression "Dünnbrettbohrer," which means literally "thin board driller.")
After I had read the paper, it turns out Fanelli had something to say about Stefan's alternative hypothesis. Before I come to that however, I have to say that I have an issue with the word "positive result." Fanelli writes that he uses the term to "indicate all results that support the experimental hypothesis." That doesn't make a lot of sense to me, as one could simply negate the hypothesis and find a positive result. If it was that easy to circumvent a more difficult to publish, less likely to be cited, summary of ones research results, nobody would ever publish a result that's "negative" in that sense. I think that in most cases a positive result should be understood as one that confirms a hypothesis that "finds something" (say, an effect or a correlation) rather than one that "finds nothing" (we've generated/analyzed loads of data and found noise). I would agree that this isn't well-defined but I think in most cases there would be a broad agreement on what "find something" means, and a negation of the hypothesis wouldn't make the reader buy it as a "positive result." (Here is a counter-example). The problem is then of course that studies which "find nothing" are equally important as the ones that "find something," so the question whether there's a bias in which ones are published is important.
Sticking with his own interpretation, Fanelli considers that researchers who come to a positive result, and in that sense show themselves correct, are just the smarter ones, who are also more productive. He further assumes that the more productive ones are more likely to be found at elite institutions. With his own interpretation this alternative hypothesis doesn't make a lot of sense, because when the paper goes out, who knows what the original hypothesis was anyway? You don't need to be particularly smart to just reformulate it. That reformulation however doesn't make a non-effect into an effect, so let's better consider my interpretation of "positive result." Fanelli argues the explanation that people smart enough to do an experiment where something is to be found are also the ones who publish more papers generally doesn't explain the correlation for two reasons: First, since he assumes these people will be at elite institutions, there should be a correlation with R&D expenditure, which he didn't find. Second, because this explanation alone (without any bias) would mean that in states where 95% - 100% of published results were positive, the smart researchers hardly every misjudged in advance the outcome of an experiment and the experiment was always such that the result was statistically significant, even though other studies have shown that this is not generally the case.
To the alternative hypothesis that Stefan suggested, Fanelli writes:
A possibility that needs to be considered in all regression analyses is whether the cause-effect relationship could be reversed: could some states be more productive precisely because their researchers tend to do many cheap and non-explorative studies (i.e. many simple experiments that test relatively trivial hypotheses)? This appears unlikely, because it would contradict the observation that the most productive institutions are also the more prestigious, and therefore the ones where the most important research tends to be done.Note that he is first speaking about "states" (which was what actually went into his study) and then later about "institutions." Is it the case indeed that the more productive states (that would be DC, AZ, MD, CA, IL) are also the ones where the most important research is done? It's not that I entirely disagree with this argument, but I don't think it's particularly convincing without clarifying what "most important research" means. Is it maybe research that is well cited? And didn't we learn earlier that positive results tend to get better cited? Seems a little circular, doesn't it?
In the end, I wasn't really convinced by Fanelli's argument that the correlation he finds is a result of systematic bias, though it does sound plausible, and he did verify his own hypothesis.
Let me then remark something about the sample he's used. While Fanelli has good arguments the sample is representative for the US states, it is not clear to me that it is in addition also representative for "all disciplines." The term "test the hypothesis" might just be more commonly used in some fields, e.g. medicine, than in others, e.g. physics. The thing is that in physics what is actually a negative result often comes in the form of a bound on some parameter or a higher precision of confirming some theory. Think of experiments that are "testing the hypothesis" that Lorentz-invariance is broken. There's an abundance of papers that do nothing than report negative results and more negative results (no effect, nothing new, Lorentz-invariance still alive). Yet, I doubt these papers would have shown up in the keyword search, simply because the exact phrase is rarely used. More commonly it would be formulated as "constraining parameters for deviations from Lorentz-invariance" or something similar.
That is not to say however I think there's no bias for positive results in physics. There almost certainly is one, though I suspect you find more of it in theoretical than in experimental physics, and the phrase "testing the hypothesis" again would probably not be used. Thing is that I suspect that a great many of attempts to come up with an explanation or a model that, when confronted with the data, fails, do never get published. And if they do, it's highly plausible that these papers don't get cited very much because it's unlikely very many people will invest further time into a model that was already shown not to work. However, I would argue that such papers should have their own place. That's because it presently very likely happens that many people are trying the same ideas and all find them to fail. They could save time and effort if the failure was explained and documented once and for always. So, I'd be all in favor of a journal for "models that didn't work."