Crowd behavior is one of the most powerful psychological forces influencing investor behavior. This tendency, sometimes called herd instinct¹, refers to the fear of “missing out” where an individual may make investments not because of careful analysis, but simply because a large group of others are doing the same. When markets are rising and optimism dominates headlines, many investors might feel a growing pressure to participate; the opposite holds true when markets decline.

As more investors pile into popular assets, prices rise further. This upward momentum reinforces the belief that the crowd must be correct. In these moments, rational thinking is often replaced by emotional decision-making, and risk is underestimated.

History provides clear examples of how this behavior can play out. During the late-1990s technology boom that led to the Dot-com bubble², investors rushed into internet-related companies with little regard for profitability, valuations, or sustainable business models. The excitement surrounding new technology created a sense that traditional rules no longer applied. When the bubble eventually burst, many who had followed the crowd suffered significant financial losses.

Even experienced investors recognize the dangers of herd mentality. Warren Buffett famously advised, “Be fearful when others are greedy, and greedy when others are fearful.” His insight highlights a key truth: markets often reach their most overheated levels precisely when confidence is at its peak.

In today’s environment, the pressure to keep up with market performance (or outperform it) can intensify these tendencies, but it often proves true to stick to long-term investment principles rather than short-term sentiment.