cognitive biases deep dive anchoring overconfidence sunk cost

This note batches eight biases that destroy trader capital. Each has a mechanism, a trading example, and a system fix.

1. anchoring

Fixating on a specific price — entry price, ATH, round number — and making decisions relative to that anchor rather than current conditions. The market doesn’t know your entry price. Fix: Trade levels, not prices. Never ask “am I up or down on this position?“

2. overconfidence

Winning streaks inflate your estimate of skill vs luck. Three winners in a row and you start believing you “figured it out.” You haven’t — you just hit the right side of variance. Fix: After every 3 consecutive wins, reduce size by 20% until a loss occurs. Hedge against your own ego.

3. sunk cost fallacy

“It’s already down 10%, I can’t sell now.” The position doesn’t know your cost basis. Sunk cost is the most expensive concept in trading. Fix: Forward-looking analysis only. The question is always “would I buy this position at the current price?” If not, close it.

4. hindsight bias

After a move, it looks obvious. “Of course the Fed cut rates.” This creates the illusion that markets are predictable. Fix: Decision journal. Write rationale before each trade. Compare pre-decision reasoning to post-hoc narrative. The gap is your bias size.

5. disposition effect

Selling winners too early, holding losers too long. Driven by loss aversion: closing a winner = realizing pleasure, closing a loser = realizing pain. Fix: Mechanical exits. Trailing stops for winners, hard stops for losers. Don’t let your brain choose the exit.

6. mental accounting

Treating money differently based on arbitrary categories. “House money” (profits from prior trades) gets risked more recklessly. Every dollar is fungible. Fix: One account, one equity curve. No mental buckets for “profits” vs “capital.”

7. confirmation bias

Seeking evidence that supports your thesis, ignoring evidence against it. Every long position has bullish news and bearish news. You read the bullish. Fix: Before entry, write 3 reasons the trade will fail. Review this list before adding to the position.

8. recency bias

Overweighting the last 10 trades. A loss streak makes you doubt your system. A win streak makes you invincible. Both are wrong. Fix: Keep a 100-trade rolling metric. Don’t change your system based on fewer than 20 trades.

see also: gn22-behavioral-finance-traps · gn27-drawdown-psychology · gn21-three-layer-trading-system

linkage

• [[gn22-behavioral-finance-traps]]
• [[gn27-drawdown-psychology]]
• [[gn21-three-layer-trading-system]]
• [[gn15-risk-of-ruin]]