Scientific research programs have life histories. They’re born with the publication of the first paper on the topic. They grow to adulthood as interest in the topic grows. They age as interest in the topic fades. They die once the last paper on the topic is published.
Previously, I’ve posted data on the life histories of some of the most influential ideas in ecological history, as measured by citation data. But those life histories presumably are atypical. What’s the life history of a typical ecological research program? What’s the typical growth rate? The typical age at maturity? The typical lifespan?
The lives of many ecological research programs are summarized by meta-analyses. Or at least, they’re summarized in part, since meta-analyses can be published before a research program dies. When are meta-analyses typically published in the life of an ecological research program? Are meta-analyses like obituaries–summaries of research programs that are now dead? Are they like retirement ceremonies–summaries of aging research programs whose most productive days are behind them? Or are they like high school yearbooks–summaries of young research programs that have most of their lives to look forward to?
Here are the data!
To get data on this, I went back to my massive compilation of ecological meta-analyses. For each of 466 meta-analyses, I have a record of when each primary research paper contributing to the meta-analysis was published. I went back to a haphazardly-selected subset of about 80 meta-analyses, and counted up how many primary research papers in the meta-analysis were published each year. That is, I’m defining “ecological research program” as “a set of primary research papers that was summarized in a meta-analysis”. And I’m quantifying the life of the research program in terms of primary research papers. A research program is born with publication of the first paper that gets included in the subsequent meta-analysis. It matures (or if you prefer, peaks) in the year in which the most primary research papers are published (or the last such year, if there’s a tie). In quantifying research interest with raw publication counts, rather than publication counts scaled relative to the total number of ecology papers published each year, I’m quantifying the absolute amount of interest in a research program, not interest relative to interest in all other ecological topics. Note that I didn’t quantify age at maturity for any research program for which no more than two primary research papers were ever published in any single year. You can’t quantify age at maturity for a research program that never develops much interest. Figuring out when a research program died would be difficult with these data, and in any case it’s clear from the data that most research programs aren’t dead yet when their meta-analyses are published. So I didn’t bother trying to quantify research program lifespan.
To anyone who wants to quibble with how I defined “research programs” or how I quantified their life histories: relax. This is just a fun, conversation-starter blog post. Live a little. 🙂
Here are illustrative results for four typical-ish meta-analyses:
You’ll notice several things. First, research programs generally start with little interest, as measured by annual number of publications. Interest grows in fits and starts over time. Second, (and this is something I’ve talked about before), interest in most research programs never gets all that high. The median research program in this compilation of 80 maxes out at just 6 publications per year! (and remember, that’s actually an overestimate for ecological research programs as a whole, because I’m ignoring data from research programs that never exceeded 2 publications/year). Third, the max (or the last occurrence of the max) usually comes close to but not at the very end of the time series. Specifically, the median peak occurs 2.5 years before the end of the time series (the mode is 1 year and the mean is 3.7 years; zero years is rare). Which, since the typical time series is a bit more than 20 years long, means that the typical research program in ecology peaks about 20ish years after it begins. Though that’s surely a bit of an underestimate of median “age at maturity”, because these data are truncated by the date of meta-analysis publication. Presumably, if those meta-analysis authors had waited longer before doing their meta-analyses, some of these research programs would’ve reached later, higher peaks. So the “age at maturation” of the typical ecological research program is a bit more than 20 years.
Of course, the max provides a noisy estimate of the peak of research interest. Probably, the “peak” for many research programs would be better described as a plateau. That’s hard to quantify. But just eyeballing all of the 80ish time series, it looks to me like, in cases where there is a reasonably distinct peak or plateau of research interest, there’s almost always just the one, and it doesn’t usually last more than 5-10 years before decline sets in. And while I haven’t shown graphs of this, in those cases where the time series includes what looks like a near-complete decline phase, the post-plateau decline phase is shorter and steeper than the pre-plateau increase phase. Ecological research programs decline faster than they grow.
Finally, ecological meta-analyses typically end their data compilation at the peak of a research program, or else a few years after the peak. Although the data truncation issue means that a minority of ecological meta-analyses may have been published well before the research program would’ve peaked in the absence of the meta-analysis.*
*I say “would have peaked in the absence of the meta-analysis” because it’s possible that publication of a meta-analysis changes a research program’s trajectory in some cases. Either by encouraging or discouraging further studies of the topic.