Market sentiment describes the prevailing emotional state of market participants: are they fearful, optimistic, complacent, or greedy? Unlike fundamental or technical indicators, sentiment measures psychology directly — through surveys, options positioning, fund flows, and market-based proxies like the CBOE Volatility Index (VIX).
The core insight from sentiment analysis is contrarian: when sentiment reaches extremes in one direction, markets have historically tended to reverse. Extreme fear (investors panic-selling, media coverage uniformly negative) has often coincided with market lows. Extreme greed (record inflows, magazine-cover euphoria, unprecedented retail speculation) has historically appeared near tops.
The practical challenge is that extremes are only identifiable in retrospect, and sentiment can stay extreme for longer than a trader can remain solvent on the other side of the bet. Sentiment is most useful as a risk management tool — prompting caution when conditions are complacent, and prompting openness to opportunities when conditions are fearful — rather than a precise trigger for mechanical trades.