İrrational investment decisions and behavioral finance

In this thesis, some deficiencies of traditional finance has been explained by referring to behavioral finance. According to the behavioral finance theorem, it has been observed that individuals take into account many factors other than risk and return when deciding that they are not rational, and while doing this, they benefit from disciplines such as sociology, psychology, social psychology and anthropology. Behavioral Finance strives to reveal the irrational situation in financial markets and the possibility of investors being wrong, that individuals are affected by the situation they are in and make investment moves. This area offers a whole new perspective on investor behavior. The addition of psychology to positive sciences has been a matter of debate in the process from the past to the present, as in this study it has been observed that psychology affects the behavior of the investor, and in this process, the individual exhibits, irrational behaviors and makes repeated judgment mistakes and is supported by examples. Thanks to the hedenometer dataset, which scores the happiness levels of the words used bythe native Arabic speakers on social media, the happiness levels were measured and the dailystock market data of the TADAWUL 30 index were compared according to the dates.Accordingly, it has been examined whether the happiness of individuals has anything to do with financial data and it has been focused on whether the emotional states of the investors that day have an effect on the decisions taken. Keywords: Behavioral finance, rationality, Prospect theory