Investor Psychology & Behavioral Finance
🧠 Why Psychology Matters More Than Formulas
Numerous studies show that most investors lose money because of emotional decision-making, not because they lack analytical formulas. Understanding cognitive biases is therefore the most important investor skill.
⚠️ The Most Dangerous Cognitive Biases
1. Loss Aversion — Fear of Loss Outweighs Joy of Gain
Kahneman & Tversky found that the pain of a loss is twice as strong as the joy of an equivalent gain. Result: investors hold losing stocks too long and sell winners too early.
2. Disposition Effect — Slow to Sell Losers, Quick to Sell Winners
A consequence of Loss Aversion — investors tend to "take profits quickly, let losses run," the exact opposite of "let your winners run, cut your losers."
3. FOMO (Fear of Missing Out)
Seeing others get rich from meme coins → buying at the peak → trapped at the top → losing money. FOMO is the main cause of buying "at the top."
4. Confirmation Bias — Believing Only What You Want to Believe
Reading only good news about stocks you hold, ignoring negative news — leading to poorly-informed decisions.
5. Recency Bias — Overweighting Recent Events
Market falls for 3 months → assume it will keep falling → sell at a loss, even though history shows markets always recover.
6. Anchoring — Clinging to Old Prices
"It used to be 100 baht, now it's 50 — what a bargain!" — even though the true value might be 30.
🔄 Bubbles & Busts
Bubbles are caused by herd behavior — everyone buys because everyone else is buying.
- Dot-com Bubble (2000) — tech stocks soared, then crashed 78%
- GFC (2008) — US real estate bubble dragged global markets down
- COVID Crash (2020) — SET fell 30% in 1 month, but recovered in 6 months
- GameStop (2021) — Reddit-driven short squeeze, price up 1,700%
- Terra/Luna (2022) — algorithmic stablecoin collapsed, $60 billion wiped out
Lesson: "Prices soaring without underlying value = a bubble" and every bubble eventually bursts.
🎯 How to Control Your Emotions
- Have a written Investment Plan — decide buy/sell rules before investing
- DCA reduces emotion — automate purchases, no need to decide every time
- Don't check your portfolio daily — monthly is enough. Frequency of checking = stress level
- Keep a Trading/Investment Journal — record the reasoning behind every decision to learn
- Take a break after 3 consecutive losses — emotional distress = worse decisions
- Read books — "The Psychology of Money" (Morgan Housel), "Thinking, Fast and Slow" (Kahneman)
