Technical analysis can generally be viewed as a search for trends or patterns in market prices. Technical analysts tend to view these trends as momentum, or gradual adjustments to 'correct' prices, or, alternatively, reversals of trends. A number of the behavioral biases discussed in the chapter might contribute to such trends and patterns. For example, a conservatism bias might contribute to a trend in prices as investors gradually take new information into account, resulting in gradual adjustment of prices towards their fundamental values. Another example derives from the concept of representativeness, which leads investors to inappropriately conclude, on the basis of a small sample of data, that a pattern has been established that will continue well into the future. When investors subsequently become aware of the fact that prices have overreacted, corrections reverse the initial erroneous trend. Efficient market advocates believe that publicly available information (and, for advocates of strong-form efficiency, even insider information) is, at any point in time, reflected in securities prices, and that price adjustments to new information occur very quickly. Consequently, prices are at fair levels so that active management is very unlikely to improve performance above that of a broadly diversified index portfolio.
In contrast, advocates of behavioral finance identify a number of investor errors in information processing and decision making that could result in mispricing of securities. However, the behavioral finance literature generally does not provide guidance as to how these investor errors can be exploited to generate excess profits. Therefore, in the absence of any profitable alternatives, even if securities markets are not efficient, the optimal strategy might still be a passive indexing strategy.