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Fear, Greed, FOMO, and Herding

The emotions that spread through crowds of investors, how they feed bubbles and panics, how they're exploited online, and practical ways to keep them from making your decisions.

Lesson 2 of 5 · 5 min read · Intermediate · Members · Last reviewed October 2026

The short version

Fear makes people sell after prices fall. Greed and the fear of missing out make them buy after prices rise. Herding, doing what everyone else seems to be doing, amplifies both. Together they can push prices far above or below what businesses are worth, and they're exactly what pump-and-dump promoters exploit. The defenses are simple and work best when set up in advance: a written plan, a waiting period before acting on excitement or fear, limits on position size, and less time watching prices and feeds.

By the end of this lesson, you'll be able to

  • Explain how fear, greed, FOMO, and herding lead investors to buy high and sell low
  • Describe how crowd behavior can feed bubbles and how promoters exploit it
  • Use practical defenses, such as waiting periods and size limits, before acting on strong emotions

Why this matters

Part 1 introduced these emotions briefly in Your Own Behavior Is Part of the Risk. They deserve a closer look, because they don't just affect individuals. When many investors feel the same thing at the same time, they move prices, and those moves pull still more people in.

Four forces

  • Fear makes a falling price feel like a threat that must be escaped now, even when nothing about the investment has changed.
  • Greed makes a rising price feel like an opportunity that can't be missed, even when the price has already run far ahead of the business.
  • , the fear of missing out, is greed's social form: the pain of watching others make money you didn't.
  • is following the crowd because a crowd feels safe. If everyone is buying, how could it be a mistake?

The SEC-commissioned report on investor behavior lists following the herd among the patterns that most often damage investors' portfolios.1

How crowds feed bubbles and panics

A rising price attracts attention. Attention brings new buyers, who push the price higher, which attracts more attention. The same report describes momentum investing, buying what has risen recently in the expectation that the trend continues, as a form of herd behavior, and notes it can give rise to speculative bubbles, such as the dot-com bubble of the late 1990s.1

The process runs in reverse in a panic. Falling prices bring frightening headlines, selling pushes prices lower, and lower prices bring more selling. In 2008, the S&P 500 lost about 37% including dividends. Investors who held on were back above their starting point by the end of 2012; investors who sold near the bottom locked in the loss.2

The rest of this lesson is for members

Still to come in this lesson: How it's exploited, Defenses that work, the key takeaways, and 2 quiz questions with explanations.

Membership opens every lesson in the curriculum, the capstone projects, the interactive tools, and the members-only channels in the Hyperion Entities Discord. The first lesson of every module stays free.

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Notes and sources

  1. Federal Research Division, Library of Congress, for the U.S. Securities and Exchange Commission. Behavioral Patterns and Pitfalls of U.S. Investors (August 2010). Checked 2026-10-06. Back to text
  2. Aswath Damodaran, NYU Stern School of Business. Historical Returns on Stocks, Bonds and Bills, with annual data through 2025 (updated January 2026). Checked 2026-10-12. Back to text
  3. Investor.gov, U.S. Securities and Exchange Commission. Social Media and Investment Fraud: Investor Alert (August 29, 2022). Checked 2026-10-01.
  4. U.S. Securities and Exchange Commission. SEC Charges Eight Social Media Influencers in $100 Million Stock Manipulation Scheme Promoted on Discord and Twitter (December 14, 2022). Checked 2026-10-06.