Leadership Nudge® 344 – Confirmation Bias

March 24, 2021by Sandy Wilmer

Here’s an interesting story about how a human brain works and how it can cause us to be confidently wrong.


So I ended up in the emergency room recently. And it’s an interesting story about how our brain works and how it causes us to be confidently wrong. So here’s what happened.  

My left calf has been bothering me a little bit, and I’ve been trying to take it easy. I had this 2.4 mile swim, no running or biking, just swimming. Shouldn’t bother my calf. My son came down for the event. 

Well, the weather was pretty rough, and there was pretty strong current. So the organizers changed the event at the last minute. And they said, what you’re going to do is swim down the beach with the current, and then run back. And you can do that four times. Now if you want to swim really fast. That’s a great way to get a PR. But the point was, now all of a sudden, there’s this running. And initially, I’m like, I’m just gonna walk back, but then you’re in the event, everyone’s passing you. And anyway, so I end up running.  

Later in the day, my left calf starts to swell up huge and pretty painful. And I got it in my head that I had a blood clot. Michael’s there and has a look at my calves.  

“Yeah, it’s really swollen up and look, I think your skin’s a little bit red.” 

And so I said, “Well, let’s go to the walk-in clinic.”  

 I’m driving to the walk-in clinic and I said Google symptoms of blood clot.  Michael reads swollen, pain, red skin, warm to the touch. I don’t know. Yeah, maybe I could have it. What else? Well, it is more prevalent in people over 60. Yeah, check. And I’m thinking that I totally have a blood clot. And now I’m starting to panic, because I don’t want it to dislodge and get in my heart and give me a heart attack or get in my head, give me a stroke.  

I rushed into the walk-in clinic, I’m like, I have symptoms of a blood clot and they’re like, go to the emergency room. We don’t have the imaging machine to confirm it. So get back in the car, we’re driving to the emergency room. Of course, I’m still driving. And we actually have this conversation, okay, if I get a stroke while I’m driving, and I’ll try for my last act to be I’ll put the car in neutral. And then you reach over grab the steering wheel and coast. Of course, if you’re having this conversation, you actually don’t want to be the person driving, but we didn’t do that.  

We show up at the emergency room, I had symptoms of a blood clot. And one of the good things about that is that I kind of moved to the front of the line. The doctor comes in.  He’s this young guy and he looks pretty athletic. He looks at me and looks at my leg. I’m going through the story of how I’m so sure it’s a blood clot. I’ve looked it up on Web MD. These are all my symptoms.  

The doctor starts shaking his head like this. And, so I stopped. The doctor said you don’t have a blood clot. I’m like, what do you mean? He’s like, you don’t get a blood clot while you’re running. You get a blood clot while you’re sedentary. I think you have a torn muscle. I was thinking no way. Then I started thinking about it. And I said, Yeah, you’re right. And I started thinking of all these reasons in the storyline. It first started this way, and it kind of came on fast and blah, blah, blah. Anyway, then my brain reframed the whole story. Long story short, I got an ultrasound that confirmed I have no blood clot. I have a torn muscle.  

This line of reasoning is called confirmation bias. What happens is when you when you get this initial hunch or idea or decision in your brain, your brain then looks for confirming information. The internet is great for this. If you type in two words, it’ll tell you how related they are and how A leads to B and B back to A.  But it’s because you searched for that. You’re actively looking for it. And this confirmation bias results in us being confidently, absolutely wrong. 

I’m David Marquet. That’s your Leadership Nudge.  

Sandy Wilmer

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