Confirmation bias (also called confirmatory bias, myside bias or verification bias) is a tendency of people to favor information that confirms their beliefs or hypotheses. People display this bias when they gather or remember information selectively, or when they interpret it in a biased way. The effect is stronger for emotionally charged issues and for deeply entrenched beliefs.
Confirmation bias is probably more prevalent among baseball fans than any other logical fallacy. We’ve all gone to a game and sat near the guy who booed when the manager brought in a mediocre reliever to try and preserve a lead, then watched the reliever implode and the loud angry fan tell everyone that “he knew” that guy was going to give up those runs. In reality, he didn’t actually know what was going to happen – since he’s really just a loud angry fan and not a fortune telling wizard – but the fact that events aligned to match his preconceived expectations led to a reinforced belief in his own prior opinion.
Since the news came out about Ryan Braun’s overturned suspension, the internet seems to be full of loud angry fans. People who “know” that Ryan Braun used steroids and got off on a technicality. People who “know” that he’s a dirty cheat. They “know” a lot of things, because Ryan Braun hits home runs, and Ryan Braun failed one drug test, and people who hit home runs and fail drug tests are cheating muscle-head juicers.
This is the unfortunate power of confirmation bias. As humans, we often take incomplete bits of information and force them into a predetermined world view because they reinforce our current belief system, and we’re wired to want to be right about things. So, despite the fact that we’re often handed pieces of information that should fall far short of being the basis for a strong opinion, we take that information as evidence that the thing we already believed to be true is indeed true, and we fortify our opinions to the point where our conclusions far outstrip what actual evidence we have.
I’m not here to exonerate Ryan Braun or declare that he’s definitely clean. I have no idea if he used steroids or not, just like I have no idea if Roy Halladay has used steroids or whether Dee Gordon has used steroids. I’m just not in any position to have any kind of opinion on what they have or haven’t done. The limited information that has gotten out to the public doesn’t give us any kind of real basis for drawing conclusions. In reality, the only thing we can ascertain from the information we have is that Bruan may or may not have used, and there’s no real way for us to actually know.
There’s nothing wrong with saying “I don’t know”, and given the actual evidence that the public possesses, it’s the only fair thing we can say. We don’t know that Braun used or didn’t use. We don’t know much about the situation, honestly. Instead of letting the small amount of information we do have reinforce our currently held opinions about home run hitters and steroid use, let’s acknowledge that confirmation bias is a powerful force and avoid the temptation to make sweeping conclusions when the information we actually have doesn’t support that kind of strong position.
Dave is the Managing Editor of FanGraphs.