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NISM-Series-X-B: Investment Adviser (Level 2) · Behavioural Finance in Practice

Market Anomalies and Behavioural Finance in Markets

Updated 11 October 2026 · Fact-checked

Market anomalies are price patterns that the Efficient Market Hypothesis cannot easily explain, such as momentum, bubbles, and calendar effects. Behavioural finance explains them through investor psychology: herding, overconfidence, and loss aversion. To solve a question, name the pattern, find the bias behind it, then pick the matching option.

Understand Market Anomalies and Behavioural Finance in Markets

The Efficient Market Hypothesis (EMH) says prices reflect all available information. Investors are assumed rational, so prices quickly move to fair value and no one can beat the market consistently after adjusting for risk. Behavioural finance says investors are only partly rational. Their biases and emotions can push prices away from fair value, and the gap can last for a long time.

A market anomaly is a pattern in prices or returns that is hard to explain with rational pricing. Common examples are momentum (recent winners keep winning for a while), reversal (long-term losers or winners later turn), the value effect (cheap stocks outperform over long periods), the size effect (small caps behave differently from large caps) and calendar effects such as the January effect or the weekend effect. Anomalies do not prove EMH is wrong in every case. Some may be compensation for risk, or may vanish once costs are counted.

Herding means investors copy the crowd instead of using their own analysis. It grows when people fear missing out, trust the actions of others as information, or want to avoid regret. In India, a rush into a hot IPO, a sector theme or small-cap stocks because everyone is buying is a typical example.

A bubble is a sharp rise in prices well above fundamental value, driven by optimism, herding, overconfidence and easy credit. A crash is a rapid fall, often driven by panic, loss aversion and herd selling. Momentum feeds the bubble on the way up. Prices often overshoot in both directions.

For the exam, keep the contrast clear. EMH: rational investors, prices equal fair value, anomalies are chance or risk. Behavioural finance: biased investors, mispricing can persist, anomalies come from psychology. As an adviser, you use this to keep clients from chasing trends and panic selling.

Key formulas to remember

EMH versus behavioural view
EMH: price = fair value (rational investors) | Behavioural: price ≠ fair value can persist (biased investors)
The core contrast. Most questions test this.
Bubble cycle
Displacement → boom → euphoria → profit-taking → panic
Typical stages. Prices rise far above fundamentals, then fall fast. Exact stage names may vary by source, so focus on the sequence.
Momentum versus reversal
Momentum: short to medium term continuation | Reversal: long term turnaround
Momentum is explained by underreaction and herding. Reversal by overreaction.
Forms of EMH
Weak: past prices | Semi-strong: all public information | Strong: public and private information
Technical analysis fails under weak form. Fundamental analysis fails under semi-strong.

How to solve Market Anomalies and Behavioural Finance in Markets questions

Use this method for any question on anomalies, herding, bubbles or EMH versus behavioural finance.

  1. 1Read the scenario and note what investors are doing: copying others, chasing winners, panic selling, or holding on.
  2. 2Match the behaviour to a pattern: herding, momentum, bubble, crash, overreaction or underreaction.
  3. 3Decide whether the question asks for the cause (the bias), the market outcome, or the adviser's action.
  4. 4Check which view the statement supports: EMH (rational, fair price) or behavioural (biased, mispricing).
  5. 5Remove options that say anomalies always prove EMH wrong or that markets are never efficient. Such absolute claims are usually traps.
  6. 6Choose the option that links the behaviour to the correct bias or pattern, and confirm it with the wording of the question.

Quickest way: Behaviour-to-label matching

When to use it: Use for short definition or scenario MCQs when time is tight.

  1. Crowd copying: herding.
  2. Rising winners keep rising: momentum.
  3. Price far above value then collapse: bubble and crash.
  4. Rational investors and fair prices: EMH.
  5. Biased investors and lasting mispricing: behavioural finance.
  6. Adviser action: keep to the plan, diversify, rebalance, avoid chasing trends.

Common mistakes in Market Anomalies and Behavioural Finance in Markets

  • Saying an anomaly proves that EMH is false.

    Students treat any pattern as clear evidence against efficiency.

    Fix: Remember that anomalies challenge EMH but may reflect risk, costs or chance. Avoid options that say 'always' or 'proves'.

  • Confusing momentum with herding.

    Both involve many investors buying the same stocks.

    Fix: Momentum is a return pattern. Herding is a behaviour that can cause it. Read whether the question asks about the pattern or the behaviour.

  • Treating a bubble as any price rise.

    Students ignore the link to fundamental value.

    Fix: A bubble needs prices well above fundamental value, driven by optimism and herding, not just a rise backed by earnings.

  • Mixing up the forms of EMH.

    The weak, semi-strong and strong names are easy to swap.

    Fix: Weak uses past prices, semi-strong adds public information, strong adds private information.

  • Saying behavioural finance assumes investors are always irrational.

    The contrast with EMH is overstated.

    Fix: It says investors are not always rational and are subject to biases. It does not say they are always wrong.

  • Suggesting the adviser should time the bubble.

    Students think the adviser should predict tops and bottoms.

    Fix: The usual answer is a disciplined plan: asset allocation, diversification, rebalancing and client education.

Worked examples

Example 1

Small-cap stocks rise sharply for several months. Retail investors buy because friends and social media posts show large gains, though valuations are far above earnings. Which behaviour best describes the buying, and what risk does it create?

Show the solution
  1. The investors buy because others are buying, not from their own analysis. This is herding.
  2. Prices are far above what earnings support. This points to a possible bubble.
  3. Such conditions can end in sharp falls when sentiment turns, as panic selling follows.
  4. So the risk is a bubble followed by a crash.

Answer: Herding; the risk is a bubble that can end in a sharp crash.

Example 2

A client says, 'Markets are always efficient, so the momentum effect cannot exist.' How would you respond using behavioural finance?

Show the solution
  1. Momentum means recent winners tend to keep outperforming for a period. This is a documented anomaly.
  2. Under strict EMH, past returns should not predict future returns, so momentum is hard to explain.
  3. Behavioural finance explains it through underreaction to news and herding, where investors follow rising prices.
  4. Do not say EMH is fully disproved. Some anomalies may fade or may reflect risk and costs.
  5. Advise the client to stay with the long-term plan and not chase past winners.

Answer: Momentum is an anomaly that EMH struggles to explain. Behavioural finance links it to underreaction and herding, though it does not prove markets are never efficient.

Exam tips

  • Expect scenario MCQs that ask you to name the behaviour: herding, momentum, bubble or overreaction.
  • Be careful with absolute words such as 'always', 'never' and 'proves'. They often mark wrong options.
  • Know the three forms of EMH and what each rules out.
  • For adviser-action questions, pick the disciplined, plan-based answer over market timing.
  • With negative marking of 25% of the marks for the question, skip only if you cannot remove at least two options.

Practice questions from Behavioural Finance in Practice

Market Anomalies and Behavioural Finance in Markets: frequently asked questions

What is the difference between the efficient market hypothesis and behavioural finance?

EMH assumes rational investors and prices that reflect all available information. Behavioural finance says biases and emotions can push prices away from fair value for long periods. The two views explain anomalies differently.

What is herding behaviour in stock markets?

Herding is when investors copy the crowd instead of doing their own analysis. It is driven by fear of missing out and trust in others' actions. It can inflate bubbles and deepen crashes.

What are examples of market anomalies?

Common ones are momentum, reversal, the value effect, the size effect and calendar effects like the January effect. They are patterns that are hard to explain with fully rational pricing.

How do bubbles and crashes relate to investor behaviour?

Bubbles build when optimism, overconfidence and herding push prices far above fundamental value. Crashes follow when sentiment turns and panic and loss aversion drive heavy selling.