Apr 24, 2012

Why Don't You Prove It?

We all like proof. Come on, admit it. How many times have you asked someone to "prove it"? Especially when they're telling you something that just doesn't sound like it could actually be true.

"No, I can't believe that! Seriously? ... Prove it!" 


As it turns out, asking for proof might not always be such a good idea. I recently came across Jonah Lehrer's article The Truth Wears Off, which was published in The New Yorker in December of 2010. In it, he writes about the so-called 'decline effect', which has recently become a heavily debated issue within the scientific community. 

When something is tested in a scientific experiment and the results are published, the test of replicability is used to ensure that these findings were not a fluke or possibly even manipulated by the scientists involved. This simply means that other researchers try to replicate these findings in subsequent experiments during the following years. Lehrer calls this "the foundation of modern research." He adds: 
"Replicability is how the community enforces itself. It’s a safeguard for the creep of subjectivity. Most of the time, scientists know what results they want, and that can influence the results they get. The premise of replicability is that the scientific community can correct for these flaws."
The only problem is: more and more often the tests of replicability do not confirm the primary findings. Instead it seems that with each new test that is carried out the findings become less clear - this is called the 'decline effect'. It is argued that "the decline effect is largely a product of publication bias, or the tendency of scientists and scientific journals to prefer positive data over null results, which is what happens when no effect is found." This in turn leads to the scientists finding ways "to confirm their preferred hypothesis, disregarding what they don’t want to see." In essence we could say that their beliefs make them blind to the truth. 

Just one of the many examples that Lehrer cites in his article is the theory of the connection between symmetry and sexual attraction. In 1991 a Danish zoologist discovered that female barn swallows were more likely to mate with males that had long, symmetrical feathers. His conclusion: Aesthetics is really about genetics. In the following three years a number of researcher were able to replicate his findings, even going so far as to test it on human behavior. It looked like the Danish guy was right.... when in 1994 the theory started falling apart. By 1998, only a third of the studies could confirm the original findings. 
Now before you go and jump off a bridge to test the declining effect of gravity, let me assure you that there is none: you're still going to fall down and die every time. The test of replicability still works for the laws of nature. Nonetheless, we have to realize that some things are probably not as factual as we would like them to be. 
Lehrer concludes his article by saying: 
"The decline effect is troubling because it reminds us how difficult it is to prove anything. We like to pretend that our experiments define the truth for us. But that’s often not the case. Just because an idea is true doesn’t mean it can be proved. And just because an idea can be proved doesn’t mean it’s true. When the experiments are done, we still have to choose what to believe."
So the next time someone asks you to prove something to them, why don't you just admit that you can't. You might want to add: "You're just going to have to believe me!" 

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