When I was a young professor, I looked down my nose a bit at professors who only published review papers, leaving all the empirical papers to their students. Now that I am a middle-aged professor, it feels like all I do these days is write review papers. Just these last few years, I have written (or helped to write) reviews for Heredity, Journal of Heredity, Philosophical Transactions of the Royal Society B, Evolutionary Applications (2), Science, Annals of the New York Academy of Sciences, Trends in Ecology and Evolution, and others. I haven’t written a true empirical paper since 2013, when I published two. Moreover, even my forthcoming book can be thought of as one long review paper.
A major reason for this shift is that “older” Professors are better known and so are increasingly asked to write reviews. Indeed, most of the review papers listed above were invited by the journals – and the others were requests to participate from younger researchers. As all of the requests came from friends or colleagues, were in good journals, and gave us the opportunity to say pretty much what we wanted, I accepted them. Of course, I also enjoyed writing them and I hope they stimulate new ideas and research interest. Or could this simply be lipstick on a pig.
Review papers have been criticized for not generating new knowledge, which presumably would be much better than simply summarizing existing knowledge. Indeed – on this blog – one post criticized review papers in eco-evolutionary dynamics for being more frequent than empirical papers in eco-evolutionary dynamics. The basic argument is that people should stop spending their time writing reviews and should instead go out and collect new data and run new experiments. Otherwise, progress in science will be stifled – or perhaps more appropriately it will be like one of those “bubbles” they talk about for sub-prime mortgages. Or a house of cards. Etc.
So what are review papers good for then – and should you take the time to write one? I would argue that – while all of the above is true – review papers (some of them anyway) are very valuable and should be deployed early and often in your career.
1. One benefit of review papers is that they bring together and synthesize a large amount of literature. So many papers are being published these days that it is impossible to keep on top of all (or even most) of them. Review papers thus become great ways to see what is in the literature in a single reading and can help to identify empirical papers that you might not have known about.
2. Another potential benefit of review papers is that they often allow more subjectivity in interpretation and more speculation. Writing an empirical paper can constrain you to only asserting conclusions that are strongly supported by the data. This constraint is good, of course, because empirical papers are specifically claiming that original data support a conclusion. At the same time, the constraint can be limiting in that empirical data might inspire new ideas that are not strictly supported by the data, yet are nevertheless good ideas that can move the field forward. Reviews/syntheses/opinions are great places to get these bold new ideas out there even if they aren’t yet supported by (much) data.
More pragmatically, review papers are great ways for younger researchers to increase their exposure. In some cases, a student can write an excellent series of empirical papers that don’t gain much attention, simply because so many papers are out there. Review papers often gain more attention (or at least exposure through citaitons) and can thereby help a young researcher become known as an expert and an original thinker in a particular area, and they can also bring attention to that researcher’s empirical papers. This pragmatic benefit was certainly the case for me, where a review paper I published just after my PhD (Hendry and Kinnison 1999 - Evolution) helped to promote the importance of contemporary (rapid) evolution and remains one of my highest-cited papers (495 citations on Web of Science, 682 citations on Google Scholar).
|Citations to all of my papers by year of publication (to 2010). Comments, responses, etc. are omitted.|
But perhaps now that I am getting longer in the tooth, I should stop writing these things – or at least so many of them. Maybe if I stopped writing so many, I could write more and better empirical papers. Maybe it is all a big trade-off and I have shifted too far to one pole. These sorts of questions got me to wondering, what would my CV look like if I subtracted all of my review papers? So I did precisely that. I downloaded Web of Science data for all of my papers, subtracted commentaries, and divided them into review papers and primary data papers.
Review papers are clearly boosting my stats or, more importantly, increasing awareness of my work. Yet the above table isn’t exactly a fair comparison given that writing review papers presumably reduces the number of empirical papers I can publish. So, on the charitable assumption that I could write roughly one empirical paper for each review paper, I simply replaced my 29 review papers with the average empirical paper (ignoring date of publication). That is, I assumed that my 29 review papers were replaced with 29 copies of my average empirical paper, yielding 149 total papers with 7181 citations and an h index of 48.
To continue the absurdity; what if all my papers were review papers? Here I replaced all 120 empirical papers with the average review paper. The stats are shown below and – if all else was equal and if citations were all that mattered – I should simply publish review papers.
Of course all else is not equal. For instance, my tendency to be invited to provide reviews might require a firm empirical footing based on original data. Alternatively (or additionally), my empirical papers might be cited more heavily because of the exposure brought by reviews. Or both, which indeed is my point. Not only are reviews good for the reasons described above but they also form a nice conceptual and promotional complement to related data papers.
In short, I strongly recommend that advanced PhD students and postdocs should write review papers. Those papers can strongly influence your research field. They will be cited. They will simulate your own thinking. They will enhance your empirical research.
As for what makes a good review paper, I have a couple of suggestions:
1. Meta-analyses are much better than conceptual thought pieces. Indeed, I have included meta-analyses in my empirical category above. Of course, the best reviews would be both – conceptual and meta-analytical.
2. Don’t just review the evidence, present new ideas and advance new hypotheses. Although you can make some hay from rehashing previous review topics, the way to make a real influence is to come up with new ideas and review new topics.
The day after writing the above, I (by coincidence) was a guest editor at the annual meeting of the board of the Annual Review of Ecology, Evolution, and Systematics, where I agreed to write another paper. And, of course, I have another paper in preparation for Trends in Ecology and Evolution, and several other reviews papers beyond those. So this trend will clearly continue for awhile longer. I am starting to really miss those empirical papers!