Investing term

What is System 1?

The fast, automatic, emotional part of the brain that reacts before you can think.

System 1 is the fast, automatic, emotional mode of thinking that reacts before deliberate reasoning kicks in — useful for snap judgments, dangerous in markets. It's what fires when a price crashes and screams "sell now." Good investing means recognizing System 1's impulses and deliberately handing the decision to slower, calmer thinking and your written plan.

For example

A scary headline triggers an instant urge to sell — that's System 1; pausing to consult your plan is letting slower thinking override it.

System 1 is taught hands-on in Stage 12 — Investor Psychology: FOMO, Panic & Biases.

See the lesson →

Related terms

AnchoringLetting one earlier number — like the price you paid — drive your judgment about a current decision.Base rateThe long-run average probability of an event, before you weight any recent evidence.Confirmation biasReading the things that agree with you and ignoring the things that don't.Disposition effectSelling winners too early to lock in gains and holding losers too long to avoid realizing the loss.
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