Your Brain Isn't Showing You Reality

Originally shared in Tuesday Notes on April 28, 2026.

Last week I told you about the two minds running your life, System 1 and System 2. The fast one and the slow one. The autopilot and the intentional thinker. Today I want to show you the first way that fast brain shapes your life without you noticing.

It's called confirmation bias.

And once you see it, you can't unsee it. Here's the simplest way to describe it:

Your brain doesn't look at the world and then forms beliefs. It forms beliefs and then looks at the world to confirm them.

So as an example: on the same day, in the same meeting, having the same conversation, two people will walk away with completely different memories of what happened, and both of them are sure they're right.

And that is not dishonesty. That is confirmation bias.

Your brain matches patterns, it is not a camera. It's constantly scanning for evidence of what you already think is true, and then quietly filtering out the rest.

The most uncomfortable place it shows up is in how you see yourself. If somewhere inside you there's a belief that you're "too much," your brain will find evidence for it. The one friend who didn't reply. The slightly "weird" tone in an email. That pause before someone answered you.

If there's a belief that you're "not enough," same thing. Every compliment slides off. Every criticism sticks.

It's not that the evidence isn't real. It's that your brain stopped collecting the other kind.

And this is the part that changed how I think about growth:

You can't just decide to believe something new. Your fast brain will keep pulling evidence for the old story. You have to actively, consciously, look for what contradicts it.

Not once. Repeatedly. Until your brain updates the pattern.

That's how beliefs actually change. Not through insight. Through evidence you make yourself notice.

So here's a small experiment for this week:

Pick one belief you hold about yourself that you're not sure is true anymore. And for seven days, collect evidence against it.

Not in a forced, positive-thinking way. Just notice, gently, when something happens that doesn't fit the story. Write it down if you want. Let it sit there.

You're not lying to yourself. You're just giving your brain the other side of the data it's been missing.

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Tuesday Brain Snack

Confirmation bias is one of the most well-studied cognitive biases in psychology, first documented by Peter Wason in the 1960s.

What's wild is that the brain doesn't just seek out information that confirms what it believes, it also remembers confirming evidence more vividly and forgets the disconfirming evidence faster so the story you have about yourself isn't just being reinforced, the counter-evidence is actively being filed away as less important, which means the work isn't finding the truth.

It's giving the truth a fair chance to be remembered.