What to believe?

With modern media, every day we are bombarded with information and claims about reality. The global economy will crash this year, red meat causes cancer, the earth is warming up, Syrian refugees cause crime, homeopathy works. The question is: what to believe and what not? Fortunately there are ways to distinguish the more credible claims from the less credible.

The quality of evidence

The likelihood of any claim being true, basically depends on one thing: the quality of the supporting (or opposing) evidence. Now, especially since the internet, you can find evidence for almost any claim you like. For instance, if you are looking for support of your flat earth belief, just visit the website of the Flat Earth Society.

The key thing to keep in mind though, is that not all evidence is equal. Some evidence is of higher quality than other evidence. And the way to determine this, is by using the scientific method.

To be clear: this does not mean science is always right! Scientists are people to, and they have prejudices and make mistakes just like anybody else. They too are poor observers, have unreliable memories, presume patterns that don’t exist and are bad at estimating probabilities.

The good thing is that the scientific method is especially designed to overcome these human shortcomings. It requires for instance that studies are properly designed, that they can be replicated by independent researchers, that results are statistical significant and that everything is published in peer-reviewed scientific journals.

Again, mistakes are frequent, so in reality the method is far from perfect, but we know by now that in the long run, it definitely works. After all, the last few thousand years science and technology have utterly transformed our world, from living in the Stone Age to the International Space Station, and that’s pretty impressive.

The scientific approach does require some background knowledge and time, two things not everybody has. Still, a number of its principles can be applied in everyday life, without first getting a Ph.D or quitting your day job.

For instance, if you’re confronted with a dubious claim, you could try to determine the quality of the supporting evidence by asking certain critical questions, like a scientist would. To give you an idea of the type of questions, I designed the Claim Credibility Checklist.

Claim Credibility Checklist

Answering the following questions will help you determine the credibility of a claim based on the quality of evidence.

Source of the claim…



Who presents the claim?


E.g. a scientist, a politician, a business person, a conspiracy theorist?



Where was the claim presented?


E.g. in a peer-reviewed scientific journal, an online newspaper, TV News, an entertainment website?



What do other sources say?


E.g. is the evidence verified by independent researchers? How much evidence is there? Did others find opposing evidence?


If a study was done…



Is it explained how the study was done?


E.g. info on the test subjects, procedure, measurements?



Was the study properly designed?


E.g. was the study large enough, was there a control group, were statistics correctly applied?



Were the right conclusions drawn?


E.g. was a causal relationship found between the variables or just an association? Are there possible alternative explanations?


Unfortunately, answering these questions can still take up quite some time. Even checking out an apparent simple claim like “a warming-up before sports prevents injuries” can easily take you a few hours of online research – if not longer. And for complicated subjects, it’s even worse.

In addition, you will constantly have to fight some major weaknesses in our human reasoning capacity. Psychologist Michael Shermer wrote in his book The Believing Brain for instance, that research showed that people tend to quickly form beliefs on emotional and social grounds and much less on a careful evaluation of the evidence. And after a belief is formed, they subconsciously seek out confirmatory evidence and ignore dis-confirmatory evidence – an effect that is called the confirmation bias.

So finding out the truth is hard work. The key is to remain an open-minded and critical thinker, demand quality evidence before accepting a claim, and eventually the truth should reveal it self.

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