“Extraordinary claims require extraordinary evidence.”
This iconic quote, popularised by Carl Sagan, resonates throughout human life as we navigate the sometimes scintillating, sometimes hazy world of knowledge that bombards our senses each day. The world is a jostling marketplace full of ideas vying for a place in our minds. How can we hope to filter it all into a viewpoint that makes sense?
Let’s look at an example. We generally accept simple claims at face value. If I (a 23 year old) said “My mother is 47 years old”, it is quite believable. It fits with widespread experience; an age gap of anywhere between about 16-35 between mother and son wouldn’t raise too many eyebrows. I doubt that the average person would demand to see documentary evidence.
Change the statement, though, and we see a different story. I’m sitting opposite you in a pub, sipping a pint of ale. I look you in the eye and say “My mother is 4 years old.” You’d laugh (or talk to someone else) but you wouldn’t believe me. If I insisted it was true, you would demand evidence. Extraordinary claim? Let’s see your extraordinary evidence.
The statement is useful when dealing with all kinds of outlandish claims, from some alternative medicines to the more extreme religious viewpoints. However, it also applies in our everyday lives, and it is especially important for scientists.
Imagine I’ve discovered a negative correlation between squirrels and heart disease rates in London – the more squirrels in an area, the less heart disease people suffer. To have this work recognised by my scientific peers, I need to convince them it’s both new knowledge and supported by evidence. If I come up with something mundane and already known, no-one would care and it wouldn’t get published. So, to meet the first criterion, I need to show how interesting my idea is, and why it’s different from what has come before.
In this case, it’s obviously new – no-one’s thought to examine squirrel distributions against heart disease rates! And, in my imaginary world, the correlation between them is strong. I boldly propose my idea: living in an area where you see lots of squirrels will lower your risk of heart disease.
Aha! But if the work is unique, and the idea is a major one, then it’s an extraordinary claim. People will demand strong evidence! Hard scientific evidence is tricky to gather and present – especially to prove causation between squirrels and less heart disease. To deal with this, I need to make sure my idea is new, but also draws on established scientific work. If I explain my finding in terms of what other people have already found, it looks less extraordinary; the burden of proof is eased.
For example, I could point to existing evidence that connecting with nature makes people less stressed; or that squirrels might prefer to live in areas with cleaner air or more open spaces where people are drawn to exercise, or some such. If I can find studies which either say, or imply, such things, it will be easier for people to accept MY new claim.
Therefore, I am faced with a dilemma. For people to notice my work, it must seem new and important. However, the level of evidence to make people believe me is relative to how new and different the work is from what has come before. If it’s a big, new discovery, I need lots of evidence; a more mundane claim, which is closer to existing work, can get away with less. I call this the ‘Scientist’s Dilemma’, faced when publishing or communicating new research.
An excellent example of the ‘Scientist’s Dilemma’ gone wrong was the Arsenic Alien Bacteria fiasco late last year. For a blow-by-blow of what happened, check out Ed Yong’s summary at Not Exactly Rocket Science. In short, the scientists and initial media promotion fell into the trap of making an extraordinary claim without the evidence to back it up, and the backlash was swift and hard. However, without the media push, the paper may have been doomed to obscurity.
I like the concept because it’s something everyone, not just scientists, can relate to. We all love telling stories and sharing ideas with other people, whether it be on a blog, out in the surf, with the local Dungeons and Dragons society or at the pub. Every time we start telling a story, if we want people to believe it, we need to keep the dilemma in mind: the more extraordinary and interesting the claim, the harder it will be to make our audience believe. Science simply takes this one step further, adding a formal structure and rules to the game of storytelling we all play.
Edit: Welcome to all those arriving from Freshly Pressed, thanks for the visit and feel free to look around! As it happens, I’m currently in the running for Best Science Blog for 2011; I’d love it if you could help me win by taking a minute and voting! More details and how to vote are here!