Have you ever been so sure of where you were going that you got lost? Or so confident in your ability that you hurt yourself? Ever reached a conclusion before looking at all the information? Let’s talk about something called “confirmation bias.”

I once had a patient bring in their son for a rash. It was a pretty straightforward case of ringworm; however, the parent swore up and down that it was not ringworm. In the end I gave them the appropriate treatment (anti-fungal cream in this case).

A while later they returned, rash and other symptoms nearly gone, only for the parent to continue insisting that it was the wrong diagnosis. Despite it being a clear-cut case of ringworm that was improving as expected with typical ringworm treatment, no amount of evidence or explanation could convince this parent otherwise. There was just no way it could be ringworm!

Similar interactions happen more often than you’d think. These interactions generally take one of two routes.

Option 1: The learning/teaching opportunity. I love this option! A chance to discuss and help patients better understand their bodies and other medical topics. 👍

Option 2: A frustrating chance to work on my patience. As in the scenario above, sometimes people are unwavering in their position regardless of any and all evidence to the contrary. These patients typically say things like: “Well I Googled my symptoms, and it said I have <insert medical ailment of choice here>. I know that’s correct and you’re stupid for thinking otherwise.” I at least try to steer these conversations to end with the patient saying, “But yes, I will try your recommended treatment. Merely to prove you wrong.” 🙄

Quick note: Option 2 does NOT mean we (doctors, PAs, NPs) are always right. We deal with our own confirmation bias too! I’m referring to situations when there is an obvious part of the bigger picture that the patient refuses to acknowledge because they are unwilling to consider another conclusion. 🙂

Bonus option 3: Hilariously frustrating. Sometimes patients come up with some very creative scenarios and/or self-diagnoses and are unwilling to consider any alternative. I’d be lying if I said it didn’t make me chuckle a bit inside. 😆

I’m going to focus on Option 2 today. Specifically how it demonstrates something called “confirmation bias.”

What is confirmation bias?

Confirmation bias is a trap we can all easily fall into. It can be reaching a conclusion before examining all of the evidence. Or sometimes it’s trying so hard to win an argument that you refuse to acknowledge any counter argument. Put a different way, it’s simply forgetting that there’s a decent chance you may be wrong. We should always be willing to be wrong. In fact, this is what makes the scientific method so effective.

Science combats confirmation bias by constantly trying to prove ourselves wrong, not simply confirm what we think may be true. That’s why proper scientific conclusions carry so much weight. And also why teaching the scientific method in school is so important, even if the sciences aren’t in your wheelhouse.

For example: I can find multiple reasons it makes sense to think Earth is flat. I can even find many people with the same observations and conclusions. We can even search for more evidence that Earth is flat and find it. That would make me pretty confident in my conclusion. But, what would happen if I searched specifically for evidence that would prove myself wrong and was unable to find any? Wouldn’t that conclusion be much stronger?

Simply searching for more evidence that we are right sets us up for being biased towards evidence that confirms our idea. Whether it’s intentional or not, we may overlook important information that does not support our conclusion. However, looking specifically for proof that we are wrong makes us less likely to miss that important information. The scientific world does this with something called the “null hypothesis.”

Preventing confirmation bias

Let’s say that I have two plants, and I think that they need water to grow and thrive. That’s my hypothesis, or educated guess based on an observation I made. More importantly, the null hypothesis in this situation is: there would be no discernible difference between the growth of the two plants whether they got water or not. To minimize confirmation bias, it’s important that I test the null hypothesis, not the original hypothesis. Therefore, I decide to conduct an experiment and stop watering one of the plants. Eventually, the plant with no water does not do as well as the plant with water. This means I can reject my null hypothesis because it wasn’t true. That does not mean that my original hypothesis (plants need water to grow and thrive) is necessarily true, but it’s not wrong. That’s a subtle but HUGE distinction. Ultimately, I tried to prove myself wrong (confirm the null hypothesis) and failed.

At its core, confirmation bias is prioritizing indications that you are right over any indication you may be wrong. It’s extremely easy to do and sneaky because confirmation bias does not necessarily mean that your hypothesis or conclusion is wrong. You might very well be correct! But the real question is, can you fail to prove yourself wrong?

Let’s say you need medication for a health issue and there are two options. The companies behind them both state that they are 99% sure there are no bad side effects. Sweet! However, the scientists who studied “medication A” conducted experiments designed to show there were no bad side effects and they found none. Alternatively, the scientists behind “medication B” conducted experiments designed to show that there ARE bad side effects with “medication B,” but they absolutely failed and could not find any evidence of bad side effects. That sounds like a pretty subtle difference, but in practice can make BIG impact. And if we’re honest, it even sounds like the people behind “medication A” were doing the right thing, trying to prove their medication was safe. But actually, it would have been much better if they tried and failed to show that their medication was dangerous, like “medication B.” It’s much harder to overlook evidence that could prove you wrong when you’re actively seeking it.

As for me, I’m taking medication B. 🙂

There’s a lot of fancy math, statistical analysis, proper experiment design and interpretation that goes on behind the results presented after a scientific study, but that’s not the point of this post. My point is: it’s much more powerful to say that you tried hard to prove yourself wrong and failed than to simply say “this information or finding supports my theory.”

Confirmation bias leads to inaccurate conclusions

Confirmation bias can cause huge problems in the medical world. For example, confirmation bias is essentially the basis of the anti-vaccine movement. Anti-vaxxers often search far and wide for evidence that vaccines are harmful, and typically disregard any evidence to the contrary. Scientists however, in an attempt to eliminate confirmation bias, conducted many studies designed to prove the null hypothesis that vaccines ARE harmful, but repeatedly failed to come up with any evidence that supported it. This is similar to the medications A and B example above. (Anti-vaxxers are “A”)

This is also part of why “Dr. Google” is so dangerous. Once we enter symptoms and the internet suggests a diagnosis, we often then begin to think of all the reasons that we DO have that condition. Unfortunately, that can cause us to be so focused on evidence that we do have a certain medical problem that we overlook the sometimes obvious evidence that we do not have that condition. Essentially, we reach a conclusion before we’ve considered ALL of the evidence. That taints how we view any further information.

Confirmation bias: IT’S A SHARK!

Truth: It certainly appears that way. Hang on…

Truth: Upon further examination this appears to be a harmless goldfish simply wearing a fake shark fin.

Confirmation bias: BUT THERE IS A SHARK FIN! ALL SHARKS HAVE FINS JUST LIKE THAT! IT’S A SHARK AND IT’S SUPER DANGEROUS!!!

Everyone struggles with confirmation bias

To be clear, your doctor or PA/NP is not immune to confirmation bias either. However, we are trained to constantly challenge our assumptions and be aware of our own biases in order to ensure accurate diagnosing. Maybe you HAVE contracted African Sleeping Sickness from a fly that you saw land on your toe in the Atlanta, Georgia airport near a gate that just had a flight return from somewhere in Africa! Or maybe that was just an ordinary fly, not an African tsetse fly, and you simply picked up a common virus after traveling through a crowded airport. Trust your doctor, not the internet. Only one of them has an medical degree. 🙂

Also remember, confirmation bias is not specific to the medical world. It shows up in many areas of our lives and keeping a close eye on our natural tendency to pursue it is a worthwhile endeavor!

Learn more, stay humble.

TL;DR: Confirmation bias is a dangerous trap that we all fall into. Sometimes we reach conclusions without considering all the information. However, we should always be willing to be proven wrong. Ultimately, trying to prove ourselves wrong and failing is more convincing than simply presenting evidence why we are right.