A 12-part series on the mental shortcuts that mostly work—and the specific situations where they’ll ruin you

You’re not as rational as you think. But you’re not as irrational as the pop psychology books want you to believe, either.

The truth is weirder, and more interesting: your brain is running software optimized for a world that no longer exists. And most of the time, that ancient code still works beautifully.

This series is about understanding when it doesn’t.

The Standard Story Is Wrong

You’ve probably encountered the “cognitive bias” literature. Survivorship bias. Confirmation bias. The sunk cost fallacy. Dozens of named ways your brain supposedly screws up.

The standard framing goes like this: Humans are irrational. We make predictable errors. Here’s a list of our bugs. Try to be more rational.

It’s not wrong, exactly. But it’s missing something crucial.

These “biases” aren’t bugs. They’re features—compressed solutions to problems your ancestors faced for millions of years. Pattern recognition. Threat detection. Social navigation. Resource allocation under uncertainty.

The brain you’re using right now kept your genetic line alive through ice ages, famines, predators, and tribal warfare. It did this not by being a perfect logic machine, but by being fast, frugal, and good enough. By taking shortcuts.

Psychologists call these shortcuts heuristics. Mental rules of thumb. Quick-and-dirty computations that sacrifice precision for speed.

And here’s the thing: in the environments they evolved for, heuristics aren’t biased. They’re optimal. They’re the best possible strategy given limited time, limited information, and limited computational resources.

The problem is that you no longer live in that environment.

The Mismatch

Your brain evolved in small groups on the African savanna. Immediate threats. Local information. Repeated interactions with the same people. Slow-moving changes. No statistics, no probability theory, no spreadsheets.

Now you live in a world of:

  • Global information (news from everywhere, context from nowhere)
  • Anonymous interactions (strangers you’ll never see again)
  • Abstract risks (market crashes, pandemic probabilities, climate projections)
  • Rapid change (entire industries appearing and disappearing in years)
  • Memoryless systems (roulette wheels, dice, random number generators)

Your heuristics were calibrated for the savanna. You’re running them in the casino, the stock market, the social media feed, the modern workplace.

Sometimes they still work. Often, actually. That’s why they persist—they’re not useless, they’re context-dependent.

But sometimes the environment has shifted enough that the shortcut leads off a cliff. And you won’t feel it happening. The heuristic fires automatically, below conscious awareness. You just act, and it feels right, and you’re wrong.

What This Series Covers

Over the next twelve articles, we’ll walk through the shortcuts your brain runs—and map exactly where they break.

Part 1: The Gambler’s Fallacy Why your brain sees patterns in randomness, and why the roulette wheel doesn’t owe you anything.

Part 2: The Availability Heuristic Why plane crashes feel more dangerous than car accidents, and why your risk model is basically your news feed.

Part 3: Survivorship Bias Why you only hear from the winners, and why “college dropouts become billionaires” is a trap.

Part 4: Anchoring Why the first number you hear hijacks every number after, and why you should always let the other person make the first offer. Or maybe the opposite.

Part 5: Loss Aversion Why losing $100 hurts more than finding $100 feels good—and why this “bias” might actually be correct.

Part 6: The Sunk Cost Fallacy Why you finish bad movies, stay in bad jobs, and hold losing positions. And how to stop.

Part 7: The Framing Effect Why “90% fat-free” sells better than “10% fat,” and how presentation hijacks decision-making.

Part 8: The Halo Effect Why attractive people seem smarter, and why first impressions color everything that follows.

Part 9: The Spotlight Effect Why you’re convinced everyone noticed your stain, and why they definitely didn’t.

Part 10: The Fundamental Attribution Error Why you judge others by their actions but yourself by your intentions—and why this wrecks relationships.

Part 11: The Dunning-Kruger Effect Why beginners feel like experts, experts feel like beginners, and calibration is a skill you have to train.

Part 12: The Shortcut Barbell Putting it together: when to trust your gut, when to override it, and how to build a life that plays to your brain’s strengths while protecting against its weaknesses.

The Approach

Each article follows the same structure:

The Mirror. A scenario where you’ll recognize yourself. No judgment—just acknowledgment that yes, you do this, because you’re human.

The Name. What psychologists call this pattern. Vocabulary matters; once you can name a thing, you can see it.

The Mechanism. What’s actually happening in your head. Not just that you do this, but why. The computational logic. The evolutionary context. The specific way the shortcut fires.

When It Works. Because these heuristics aren’t stupid. In most of life, they’re adaptive. We’ll identify the environments where the shortcut is actually correct.

When It Breaks. The specific conditions—usually modern, usually abstract, usually involving statistics or strangers or memoryless systems—where the heuristic fails.

The Move. One question, one practice, one reframe you can actually use. Not “be more rational.” Something concrete.

What This Series Isn’t

This isn’t a catalog of ways you’re broken. The “look how dumb humans are” genre bores me.

It’s also not a promise that you can transcend your cognitive limitations through sheer awareness. You can’t. The heuristics fire whether you want them to or not. Knowing about the Gambler’s Fallacy doesn’t make the roulette wheel feel any less “due” for a correction.

What you can do is build systems. Create decision environments that protect you from your own shortcuts. Know which domains are dangerous and slow down in those domains. Develop habits and practices that route around the failure modes.

You can’t upgrade the hardware. But you can choose which situations to put it in.

The Barbell Preview

Here’s where this series is heading:

Your brain’s shortcuts are ecologically rational—they’re adapted to specific environments. In those environments, trust them. They’re fast, they’re frugal, and they’ve been battle-tested for a hundred thousand generations.

But some environments are new. Memoryless systems. Abstract statistics. One-shot interactions with strangers. Fat-tailed distributions where rare events dominate. These are the zones where ancient software meets alien terrain.

The move is a barbell:

In familiar territory, where the environment matches the ancestral pattern: trust the gut. Move fast. Let the heuristics do their job.

In novel territory, where the environment is abstract, statistical, or evolutionarily unprecedented: slow down. Check the math. Override the instinct.

The dangerous place is the middle—using gut instincts in alien environments while feeling confident because the instinct feels so right.

Confidence isn’t calibration. Fluency isn’t accuracy. And your brain can’t tell the difference.

But you can learn to ask: Is this situation the kind my shortcuts evolved for?

That question is worth twelve articles to answer properly.

Let’s start.

Start reading: Part 1 — The Roulette Wheel Has No Memory