🧠 Trading psychology: the biases that cost traders money

🎯 In 30 seconds: Most trading mistakes are not about missing information. They come from predictable habits of the human mind. People feel losses about twice as strongly as gains, so they hold losers and sell winners too soon. They overrate their own skill, so they trade too much. They chase moves they fear missing, copy what a crowd in a WhatsApp or Telegram group seems to be doing, and try to win back losses with bigger bets. You cannot switch these habits off, but written rules, small position sizes and a review routine can keep them from making your decisions.

The screenshot in the group chat

It is 11 a.m. on a weekday. Someone in your college group posts a screenshot: ₹38,000 profit on a Nifty option, made in 40 minutes. Three people reply with fire emojis. Someone asks for "the channel link". By lunch, two friends have joined a stock tips group you have never heard of.

Nobody posted their losses that morning. Nobody asked how much was risked. The screenshot did its work anyway, because it hit three habits at once: fear of missing out, trust in what a crowd seems to be doing, and the belief that if they can do it, so can you.

This chapter names those habits. Knowing their names helps you spot them, and knowing they are normal helps you build rules that work even on bad days.

Why psychology belongs in a risk chapter

You can know every rule in this course and still break them in the moment. A stop gets moved "just this once". A position gets doubled after a loss. A stock gets bought because it hit the upper circuit twice this week and everyone is talking about it.

These are not random. Researchers have documented the same patterns in millions of real trades, and SEBI's own studies of Indian traders show their fingerprints. The good news is that the fixes are mostly mechanical.

Loss aversion: losses hurt more than gains feel good

In 1979 psychologists Daniel Kahneman and Amos Tversky published prospect theory, a description of how people actually make choices under risk. One central idea is loss aversion: a loss feels worse than a gain of the same size feels good.

In their 1992 follow-up, the typical estimate was that losses weigh about 2.25 times as much as equal gains. Later studies vary, but a ratio around 2 is the usual rough figure. Kahneman received the Nobel memorial prize in economics in 2002, partly for this work.

What it does to traders:

• You avoid closing a losing trade, because closing makes the loss "real" in your P&L.
• You turn down good trades after a loss, because another loss would hurt too much.
• You take on extra risk to avoid a sure loss, for example holding a falling stock and hoping, or averaging down into it, rather than accepting a small loss now.

The disposition effect: selling winners, holding losers

In 1985 Hersh Shefrin and Meir Statman named the disposition effect: the tendency to sell winning investments too soon and hold losing ones too long.

Terrance Odean tested it in the trading records of 10,000 accounts at a large US discount broker from 1987 to 1993. Investors sold 14.8% of the gains they had available to take, but only 9.8% of the losses. They were about one and a half times as likely to sell a winner as a loser.

It was also costly. The winners investors sold went on to beat the losers they kept by 3.4 percentage points, on average, over the following year. The study used US data, but the pattern is familiar to anyone who has watched a demat account fill up with old losers bought on tips, still held "until it comes back to my price".

The fix is mechanical: a stop order decided before entry (see Stop losses) and an exit rule for winners that you wrote down in advance.

Overconfidence: trading too much

Overconfidence means believing your knowledge or skill is better than it is. It shows up as trading too often, concentrating in a few favourite ideas and underestimating risk.

Brad Barber and Terrance Odean studied over 35,000 US households at a discount broker from 1991 to 1997. Men, who in psychology studies tend to be more overconfident about finance, traded 45% more than women. Trading cut men's net returns by 2.65 percentage points a year, against 1.72 for women. The lesson is not about gender. It is that more trading, for most people, meant lower returns, because costs are certain and skill was not.

SEBI's Indian data points the same way. In its study of intraday trading in the equity cash segment, 71% of individual traders made net losses in FY23. Among the most active, those making more than 500 trades a year, the share of loss-makers rose to 80%.

Sunk cost: why losing traders keep going

Sunk cost thinking is holding on because of what you have already lost or spent. "I can't stop now, I'm down ₹60,000, I need to make it back." The only question that matters is whether the next trade has a positive expectancy. Past losses do not change that.

SEBI's September 2024 study of F&O traders found that more than 75% of loss-making traders continued trading F&O despite losses in consecutive years. Some of that may be learning. A lot of it looks like the urge to win back what is gone.

FOMO, herding and manufactured social proof

FOMO (fear of missing out) is buying because a price is rising fast and others seem to be making money, not because your plan says so. FOMO entries tend to be late, far from any sensible stop, and therefore either oversized or unprotected.

Herding is doing what the crowd does because the crowd is doing it. It feels safe. In markets it often means buying near the top of a move, after the early buyers are already looking to sell.

India has a particular version of this: tip groups on WhatsApp and Telegram. SEBI has warned about them repeatedly. In a press release dated 22 October 2026, SEBI said unregistered persons were sharing buy and sell calls in invitation-only WhatsApp groups, often from overseas numbers, under the label of free investor education. To make the calls look credible, some members acting with the operators post false profit claims and praise the "expert". SEBI called this astroturfing: creating a false impression of genuine support so that real members act on the calls.

In other words, the social proof is manufactured. The screenshots, the "booked profit, thank you sir" messages and the rush of agreement are part of the product. SEBI's advice includes not joining such groups, not being swayed by praise or profit claims from other members, treating a "our old group was banned, join the new one" message as a red flag, and dealing only with SEBI-registered intermediaries and authentic trading apps.

An earlier SEBI caution, in April 2025, listed common lures such as "VIP group", "institutional trading group" and "investment club", and promises of IPOs or block trades at a discount. More on spotting these in Scams and red flags.

Revenge trading and other common patterns

Revenge trading is trying to win back a loss quickly with a bigger or rushed trade. Here is how it plays out on a hypothetical ₹2,00,000 account with a normal risk of ₹2,000 per trade:

The three planned losses were normal. The one emotional trade did more damage than all three. In F&O the revenge trade is often an out-of-the-money option bought on expiry day because it is cheap. Cheap is not the same as low-risk: the whole premium can go to zero by 3:30.

Confirmation bias is seeking out information that supports what you already believe and ignoring the rest. Once you own a stock, you notice the bullish posts and skip the bearish ones. Social media feeds make this worse, because they show you more of what you already clicked on. Counter it by writing down, before entry, what would prove you wrong.

Anchoring is fixing on a number that does not matter, such as the price you paid, the IPO price or a stock's old high. The market does not know your entry price.

Recency bias is giving the last few trades or days too much weight. Three wins make you feel unbeatable; three losses make you abandon a sound plan.

The gambler's fallacy is believing a run must reverse: "it has fallen five days in a row, it has to bounce." Prices do not owe you a bounce.

Routines that help

None of these habits go away by deciding to be disciplined. What works is setting up your process so the right action is the easy one.

1. Decide before 9:15. Write the setups you will take, with entries, stops and sizes, the evening before or before the open. During the session you execute, you do not invent. A written trading plan is the backbone.
2. Keep size small. Losses of 0.5% to 1% are easy to accept. Most emotional mistakes start with a position big enough to scare you.
3. Use a daily loss limit. For example, after 3% down in a day or three losses in a row, you log out for the day. This blocks revenge trading before it starts.
4. Place stops as real orders. It removes the moment where loss aversion gets a vote.
5. Use if-then rules. "If the stock closes below ₹379, then I sell at the next open." Decisions made in advance hold up better under stress than intentions.
6. Mute the noise. Leave tip groups, mute finance channels during market hours and turn off app notifications that are not your own price alerts.
7. Log your emotions. Add one line to your trading journal for each trade: calm, rushed, bored, angry, fearful, "saw it in a group". After a month, check which mood goes with your worst trades.
8. Take breaks. Step away after a big win or a big loss. Both push people toward bigger risks.
9. Review weekly, not trade by trade. Judge your process over many trades. One trade is mostly luck.

Try it

For your next 20 trades, real or practice, add three columns to your journal: "followed plan? yes/no", "mood at entry" and "where did the idea come from?" (my own scan, news, a friend, a group, a video). At the end, compare the average result in R for each source and for the yes and no trades. Then find your two worst trades and name the bias behind each one using the list above. If you are in any stock tips group, read SEBI's October 2026 press release and check the group against each warning sign it lists.

Sources

• SEBI press release (22 October 2026): Caution to investors against stock tips offered through invitation-only WhatsApp groups
• SEBI press release (11 April 2025): Caution to public against fraudulent and manipulative activities on social media platforms
• SEBI (July 2024): Analysis of intraday trading by individuals in equity cash segment
• SEBI press release (23 September 2024): 93% of individual traders incurred losses in equity F&O between FY22 and FY24
• Kahneman and Tversky, Econometrica (1979): Prospect theory, an analysis of decision under risk
• Tversky and Kahneman, Journal of Risk and Uncertainty (1992): Advances in prospect theory
• Odean, Journal of Finance (1998): Are investors reluctant to realize their losses?
• Barber and Odean, Quarterly Journal of Economics (2001): Boys will be boys