Dec 13 2010

The Decline Effect

While there is a complex spectrum of attitudes toward science, there are three clusters worth pointing out, specifically in reference to the provocative New Yorker article by Jonah Lehrer called The Truth Wears Off. The first group are those with an overly simplistic or naive sense of how science functions. This is a view of science similar to those films created in the 1950s and meant to be watched by students, with the jaunty music playing in the background. This view generally respects science, but has a significant underappreciation for the flaws and complexity of science as a human endeavor. Those with this view are easily scandalized by revelations of the messiness of science.

The second cluster is what I would call scientific skepticism – which combines a respect for science and empiricism as a method (really “the” method) for understanding the natural world, with a deep appreciation for all the myriad ways in which the endeavor of science can go wrong. Scientific skeptics, in fact, seek to formally understand the process of science as a human endeavor with all its flaws. It is therefore often skeptics pointing out phenomena such as publication bias, the placebo effect, the need for rigorous controls and blinding, and the many vagaries of statistical analysis. But at the end of the day, as complex and messy the process of science is, a reliable picture of reality is slowly ground out.

The third group, often frustrating to scientific skeptics, are the science-deniers (for lack of a better term). They may take a postmodernist approach to science – science is just one narrative with no special relationship to the truth. Whatever you call it, what the science-deniers in essence do is describe all of the features of science that the skeptics do (sometimes annoyingly pretending that they are pointing these features out to skeptics) but then come to a different conclusion at the end – that science (essentially) does not work.

I often feel that those in this third group – the science deniers – started out in the naive group, and then were so scandalized by the realization that science is a messy human endeavor that the leap right to the nihilistic conclusion that science must therefore be bunk.

But scientists themselves are generally in the middle group (at least they should be), and so news about the various foibles of science is no surprise.

The New Yorker Article

The article by Lehrer falls generally into this third category. He is discussing what has been called “the decline effect” – the fact that effect sizes in scientific studies tend to decrease over time, sometime to nothing. This term was first applied to the parapsychological literature, and was in fact proposed as a real phenomena of ESP – that ESP effects literally decline over time. Skeptics have criticized this view as magical thinking and hopelessly naive – Occam’s razor favors the conclusion that it is the flawed measurement of ESP, not ESP itself, that is declining over time.  Lehrer, however, applies this idea to all of science, not just parapsychology. He writes:

And this is why the decline effect is so troubling. Not because it reveals the human fallibility of science, in which data are tweaked and beliefs shape perceptions. (Such shortcomings aren’t surprising, at least for scientists.) And not because it reveals that many of our most exciting theories are fleeting fads and will soon be rejected. (That idea has been around since Thomas Kuhn.) The decline effect is troubling because it reminds us how difficult it is to prove anything. We like to pretend that our experiments define the truth for us. But that’s often not the case. Just because an idea is true doesn’t mean it can be proved. And just because an idea can be proved doesn’t mean it’s true. When the experiments are done, we still have to choose what to believe.

This paragraph sums up what I was describing above – Lehrer is ultimately referring to aspects of science that skeptics have been pointing out for years (as a way of discerning science from pseudoscience), but Lehrer takes it to the nihilistic conclusion that it is difficult to prove anything, and that ultimately “we still have to choose what to believe.” Bollocks!

Lehrer is describing the cutting edge or the fringe of science, and then acting as if it applies all the way down to the core. I think the problem is that there is so much scientific knowledge that we take for granted – so much so that we forget it is knowledge that derived from the scientific method, and at one point was not known. Many conclusions in science do not decline over time – they strengthen, and they become so overwhelmingly confirmed that they can be treated as established facts (although  always open to revision). The theory of gravity, relativity, evolution, the DNA basis of genetics, the germ theory of infectious disease – these are not illusions that evaporate under closer scrutiny, but fundamental aspects of reality that science has elucidated.

It is telling that Lehrer uses as his primary examples of the decline effect studies from medicine, psychology, and ecology – areas where the signal to noise ratio is lowest in the sciences, because of the highly variable and complex human element. We don’t see as much of a decline effect in physics, for example, where phenomena are more objective and concrete.

The Decline Effect

If the truth itself does not “wear off”, as the headline of Lehrer’s article provocatively states, then what is responsible for this decline effect? The answer can be found in the previous articles of this blog and many others, like science-based medicine. But to quickly review – it is no surprise that effect science in preliminary studies tend to be positive. This can be explained on the basis of experimenter bias – scientists want to find positive results, and initial experiments are often flawed or less than rigorous. It takes time to figure out how to rigorously study a question, and so early studies will tend not to control for all the necessary variables. There is further publication bias in which positive studies tend to be published more than negative studies.

Further, some preliminary research may be based upon chance observations – a false pattern based upon a quirky cluster of events. If these initial observations are used in the preliminary studies, then the statistical fluke will be carried forward. Later studies are then likely to exhibit a regression to the mean, or a return to more statistically likely results (which is exactly why you shouldn’t use initial data when replicating a result, but should use entirely fresh data – a mistake for which astrologers are infamous).

All of these effects, and more, are why skeptics are frequently cautioning against new or preliminary scientific research. Don’t get excited by every new study touted in the lay press, or even by a university’s press release. Most new findings turn out to be wrong. In science, replication is king. Consensus and reliable conclusions are built upon multiple independent lines of evidence, replicated over time, all converging on one conclusion. But such conclusions are possible, and occur so often we take them for granted. While initial conclusions that turn out to be wrong are sensational – as is turning such events into an indictment of science itself.


Lehrer does make some good points in his article, but they are points that skeptics are fond of making. In order to have a  mature and functional appreciation for the process and findings of science, it is necessary to understand how science works in the real world, as practiced by flawed scientists and scientific institutions. This is the skeptical message.

But at the same time reliable findings in science are possible, and happen frequently – when results can be replicated and when they fit into the expanding intricate weave of the picture of the natural world being generated by scientific investigation.

But apparently it is more provocative to focus on the edges of science where results are preliminary and replication calls them into question. It is true that often preliminary results are seized upon, and in medicine even acted upon, before they are adequately confirmed. That is an important lesson. But it does not mean that science doesn’t work. It just means that science grinds more slowly than perhaps we would like. Science is self-corrective, and perhaps there is more to correct than we would like. But in the end the process of science works itself out. It is not just another narrative, and we don’t have to arbitrarily choose what to believe.

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