Stop Using Personal Anecdotes To Discredit Science

by Katie Cloyd
Originally Published: 
Scary Mommy and Deagreez/Getty

We need to talk about the difference between anecdotal evidence and scientific fact. I’m not a scientist, so this isn’t going to be a lofty academic explanation. I’m just coming to you as a friend who wants to encourage you to make good choices and keep your eyes on verifiable truth.

Let me tell you a true story: Every single time I’ve gotten a positive pregnancy test, I’ve seen a rainbow that exact same day. I’ve had three children and two other pregnancies, so that is FIVE times in my life that I’ve seen a rainbow the same day I found out I was pregnant. Isn’t that something? When I saw the rainbow the day I found out about my last baby, I literally gaped at it like I’d never seen one before. It felt so impossibly coincidental.

No matter how significant it felt, my experience doesn’t mean I can now claim that when I pee on a First Response it changes the color of the sky. Rainbows are the result of light and water playing together in the atmosphere. They are in no way connected to my decision to reproduce or urinate on a piece of plastic — no matter how absolutely one-in-a-million (five-in-a-million?) the experience felt to me.

Correlation doesn’t equal causation.

I have no mathematical clue what the odds are that I would see a rainbow every single time. But I’ll tell you the odds of the two events actually being connected.


There’s a zero percent chance the two have anything to do with one another. Even though they feel connected to me.

Anecdotes are not data.

They’re just personal stories. Anyone can tell them, and there is no way to verify their authenticity. They’re subject to a person’s memory (you’d be shocked how poor and easily manipulated human memory can be) and filtered through their personal experiences. Anecdotes can be amusing, emotional and interesting. They can even be a good reason to do further study.

Using anecdotal evidence to discount peer-reviewed science is dangerous. Even when a person is very adamant and believes they are telling the entire truth with no discrepancies, anecdotes just can’t be used in place of actual scientific facts.

It’s an especially good idea for all of us to remind ourselves of this fact right now. We are watching a mass vaccination campaign take place in real time in response to a global pandemic. Millions of vaccines are being administered to the oldest and most vulnerable people among us every day. Long story short, shit’s going to happen to some people soon after being vaccinated. It doesn’t mean that shit is connected to the vaccine. We can’t let every scary-sounding story send us running for the hills.

There are a lot of decisions to make for schools and businesses. Even after taking the vaccine, people need to continue to follow COVID guidelines. We need sound science to be the loudest voice right now. Our safety and survival depend on it.

But honestly, it’s also just a good idea ALL the time to remember that anecdotes are not facts. Personal stories ARE NOT data. If we start listening to our hearts, following our guts or believing Jessica from Facebook instead of peer-reviewed scientific consensus, we are going to make really stupid choices—during this pandemic and way beyond.

Anecdotal evidence is actually not evidence at all.


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Think about it.

Your rude uncle laughs at you for putting your kindergartener in a five-point harness. “When I was a kid, I rode in a truck bed going down the highway at 60 miles per hour and I survived!” He isn’t taking into account all the people who aren’t alive to mock you because they died in auto accidents before modern car seats were available.

That veteran mom who rolls her eyes at you for cutting your kid’s food? She let her kids eat whole grapes as babies and they didn’t choke. She isn’t thinking about the grieving parents who would do anything to go back and slice up the grape or hot dog or carrot into smaller pieces.

There’s always someone who rolls their eyes when you breastfeed your child in public. She didn’t breastfeed her kids, and they’re all perfectly healthy. She thinks that means breast milk has no health benefits and public nursing is a performance. This woman isn’t thinking about babies in the NICU whose lives have been saved by donor milk.

Or my current personal pet peeve: The people who have been throwing caution to the wind and haven’t gotten sick during this pandemic yet, so they have decided people like me who are staying home and wearing masks are idiots who are living in unnecessary fear. Never mind that the data clearly shows COVID is much more lethal than the flu.

Each of these examples elevates personal experience over actual truth.

It can be so confusing when you get swept up into a tornado of anecdotes.

But don’t worry. There’s an established hierarchy of evidence. It has layers. (Anyone else hear that in Shrek’s voice? No? Just me?)

At the very top of the pyramid, you have a process where experts collect all the data from multiple properly constructed relevant studies and trials. They determine whether the methods were good and verify that the conclusions of the studies are in agreement. If they all agree, and if they all used proper science and can replicate their outcomes, they decide it’s reasonable to trust their conclusions. Experts feel justified making recommendations and decisions based on that evidence.

Various other types of data fall on other tiers. It starts with a single well-designed study reviewed by qualified peers, and trickles down through various other types of less ideal experiments and trials. Eventually, you get all the way to the very bottom where pretty much every super smart, educated person alive agrees that the evidence can’t be trusted enough to use it to make medical or policy decisions.

There at the very bottom of the pyramid is where you find single case studies and personal observations, AKA anecdotal evidence. These kinds of stories are the least likely to be accurate. They are basically discarded except as a jumping off point for further research.

This is why you can’t use anecdotal evidence to inform your life choices.

It is unwise and dangerous to dismiss the entire body of scientific evidence because some random person in your life or online swears their experience says otherwise.

We live in a world where immense amounts of information come flying at us every single day. Anyone can say anything, and really smart people can make it all sound incredibly convincing.

But they can also be super wrong.

It’s so important now and always to vet your sources, listen to credentialed experts and make sure that you can tell a personal story from a scientific fact.

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