[EN]When we talk about financial markets, we usually talk about falls or rises occurring in them, the earnings of enterprises and their strategic plans... Throughout history a lot of theories and studies have been carried out on them, being the Theory of Efficiency the most one accepted nowadays. But in all of this, there is a great forgotten that is not usually taken into account and that is an important factor, if not the most, in the markets, which is none other than humans. The work is based on the confrontation, practical and theoretical, between the Theory of Efficiency on financial markets and the Theory of Behavioral Finance, with the objective of generating samples in order to see if markets are efficient or irrational. After all, decisions of buying or selling, to acquire a fund or bonds are held by humans. Therefore, in the effort to understand financial markets, understanding human psychology is something essential. Inglés