Aspectos comportamentais associados às rea？？es do mercado de capitais

in this article, it will be presented the basics, empiric evidences and alternative models of behavioral finance that attempt to identify market reactions potentially influenced by the investor's psychology. it will be implemented a quantitative methodology of evaluation of abnormal price reactions, in order to investigate the viability of contrarian and momentum strategies, in the specific case of assets from the brazilian stock market. when it is not considered adjustments by the risk level, results suggest the existence of influence from investor's behavior in the market. such influence is reflected in the higher profitability, at the 5% significance level, of the momentum strategies between the thirteen to fifteen week's horizons after investments. but when it is performed the adjustment of returns by systematic risk, results do not allow rejecting the hypothesis of efficiency of the market portfolio, and thus, the contrarian or momentum strategies do not allow extraordinary gains.