“Putting your money where your mouth is”, also known as “betting your beliefs”, is a form of honest signalling: it’s a way of demonstrating that your beliefs are sincerely held, and that you’re willing to stand behind them. As economist Alex Tabarrok says, “a bet is a tax on bullshit”.
Of course, bullshit is relatively rarer in science than in other fields (Tabarrok’s discussion concerns political punditry and political election forecasting). But more broadly, a bet is a tax on being wrong. Insofar as your beliefs about the world are mistaken (or at least, more mistaken than the beliefs of whoever takes the other side of the bet), you expect to lose money. This is the logic behind prediction markets. Perhaps their most famous use is election forecasting, but they’ve been used to allow betting on scientific topics such as the reality of cold fusion.
Ecologist Paul Ehrlich and economist Julian Simon famously wagered on whether the inflation-adjusted prices of five metals would increase or decline during the 1980s. Ehrlich thought prices would increase because human population growth was outstripping growth in resource supply. Ehrlich lost. And while one could argue that in a larger or broader sense Ehrlich was right about the consequences of human population growth (indeed, many have argued precisely that), part of the point of a bet is that it forces the bettors to state their claims precisely enough to make a wager possible.Vagueness is where our biases, implicit assumptions, and faulty logic hide. In forcing you to be precise, betting is rather like mathematical modeling, and that’s a good thing. And if you find you’re unable, or unwilling, to make your beliefs precise enough to be willing to bet on them, well, that in itself is useful for you (and others) to know.
One famous scientific bet involved Alfred Russel Wallace, but it was nothing to do with evolution. Wallace bet a flat-earther named John Hampden that he could prove the Earth was round. Wallace, a qualified surveyor, won the bet with a famous surveying study now known as the Bedford Level experiment. The bet was for a lot of money (the equivalent of 35,000 pounds sterling today!), but Hampden never paid and instead took to threatening Wallace. More recently, Steven Hawking lost a bet on whether the Large Hadron Collider would discover the Higgs boson. Here is a list of prominent scientific bets, both historical and current, including many as-yet-unresolved ones. Many of them are from physics and none are from ecology, although a few involve bets or proposed bets on global warming. Physics bets are common enough that they’ve even been made the subject of a cartoon.
Far, far less notably, as a grad student I once made a bet with Hal Caswell and Mike Neubert over whether a particular food web model had a stable, feasible equilibrium or not. I said it did, they said it didn’t, I won, and they had to buy me a beer. In fairness, I don’t know that they were seriously betting their beliefs–I think it was more just a bit of fun and a way of testing me a bit (the condition of the bet was that I had to prove the stability and feasibility of the equilibrium myself; I couldn’t just go look up a paper on the model). Indeed, I now suspect that they may well have intentionally made a bet they knew or suspected they’d lose, much as a parent might let a child win at a board game. 🙂
I’m still trying to think of some ecological claims I’d want to bet on. Part of the problem is that my recent blog posts and paper on the zombie IDH have given away a number of “sucker bets” that I might have hoped to get someone to take (e.g., a bet on whether fluctuating mortality rates can make stable coexistence of competitors possible in a linear additive model). 🙂 Similarly, it’s too late to bet on the outcome of the NutNet study showing that the diversity-productivity relationship in grasslands is not humped. I kind of wish the NutNet folks had thought to make a bet with believers in the universality of humped diversity-productivity relationships before the NutNet study began. I think such a bet (or even just the exercise of trying to define a precise, mutually-acceptable bet) would’ve been very interesting. So I need to think of some as-yet-unresolved ecological controversies on which I’d be willing to bet on the resolution…
What ecological claims would you want to bet on, and at what odds? As Tabarrok notes, the odds are key–if you think the odds are fair, you should be willing to take either side of the bet. And if you can’t think of any, is that a bad sign for ecology? A sign that we’re bad at prediction, to the point where we’re too uncertain to be willing to make any bets?