Citation Vacuums

In science, there’s a simple currency earned by important publications: citations by subsequent papers. Each citation gives credit, a small nod of recognition, a karma point, a feather in the cap. We are proud when our publications garner many citations. Citation count, however, is not a great metric of true quality or impact: all that glitters is not gold; all that is gold does not glitter. Counting citations sometimes credits authors with a greater part in advancing the field than they deserve, and fails to credit those who do.

I remember many years ago hearing David Swofford, the author of the widely-used PAUP program for analyzing evolutionary trees, grumbling about a paper just published. His complaint was that the paper’s “novel” concept wasn’t particularly novel — it was so obviously implicit in the literature’s ideas that none among the most theoretically astute biologists thought it was worth publishing in a standalone paper. And yet, the paper was published, and received attention precisely because no other paper had previously said that useful (though obvious) idea so directly.

Such gap in the literature is a “citation vacuum“, a region of “idea space” that is well within the current paradigm, but unoccupied by a citable paper. Over the years I’ve seen several vacuums exploited to the career benefit of their discoverers. We scientists like to cite compact, precise, and strong statements of an idea, and if none exists, then there is a vacuum in the literature waiting to be filled. It doesn’t matter if the idea is already understood by many, or if the idea is in fact already in the literature but in a long-forgotten paper or buried on page 9 of a software manual. It only matters that there is no obvious paper to cite, and if you write one, cha-ching, the citations come rolling in.

I’m reluctant to name names. Most authors who’ve written vacuum-filling papers probably don’t think of them as such, instead believing them highly novel, and I wouldn’t want to disturb their glory. I will mention one name, however — my own. My best cited paper is my 1997 paper “Gene Trees in Species Trees”. When I wrote it, I didn’t think of it cynically as a vacuum-filler, but in many ways, that’s what it was. It was a condensation of the Zeitgeist, gathering together and organizing ideas that probably were already, in large part, in the heads of the leaders of the field. It’s become a magnet for citations because it’s accessible and provides a compact citation for the field’s perspective. It’s a pedagogically useful paper, but I expect that it brought the median understanding in the field forward more than it informed those at the cutting edge.

So, go find a vacuum, publish, and profit*.

*To be clear: I’m not advocating that you withhold credit to your predecessors. Please, when filling a vacuum, look for and cite the papers that set up (or perhaps even mention) your idea. Treat your paper as a new attempt to synthesize and explain ideas already in the conversation of the field. Take credit for the clarity and thoroughness of your exposition, because those may be new, and will add value to the field.


Remembering Fred Wanless

Back in the old days (i.e. pre-web) it was hard to connect with others with common interests, at least when your interests were uncommon. By the time I was a graduate student, I’d been studying jumping spiders (salticids) for a decade, but had met precious few experts on my favourite spiders. Conferences were a rare chance to chat real-time with your far-away role models and comrades, and maybe find someone with whom you could speak at the speed of your excitement.

As a 28 year old, in 1986, I flew to Spain for my first International Congress of Arachnology (and my first visit to Europe), where I met Fred Wanless, an arachnologist at the British Museum of Natural History (now known pretentiously as The Natural History Museum). His publications on jumping spider systematics combined two strengths that were unique at the time: they examined salticid diversity broadly across phylogeny and geography, and they used cladistic logic to discuss evidence for jumping spider phylogeny. My recollection was that we met at a bar in Jaca; he was humble, uncomplicated, sincere. Talking to him was amazing — “Do you think Lapsias could be a spartaeine?” “Do you think an articulated embolus is an important character?” — and on and on. I left the evening feeling as if I had just flown through the forests of Endor on a speeder bike.

Fred died last month. We arachnologists hadn’t heard much from him for many years, because he had been forced in 1990 to stop studying spiders, told to study instead the more “relevant” nematodes. His departure from salticidology deprived us of a colleague and years of important publications (though no doubt the nematologists appreciated him). But his 1980s publications remain a cornerstone of our literature for the knowledge that they gained, and also for the model they provided: well illustrated, well argued, well organized. When I wrote a recent paper reviewing the phylogeny and classification of all jumping spiders, his papers were the first I went to, to pour over their data and interpretations.

I phoned Fred about 12 years ago to ask a question about a notable specimen I thought he might remember. His thoughts were far from jumping spiders, having drifted first to worms then to retirement projects. I told him how important his papers had become to us, and he was surprised — still humble and uncomplicated. We were lucky to have had him in our literature, and in our community.