My research interest lies in the critical examination of efficient financial markets. In efficient (or rational) financial markets asset prices fully reflect all available information. Market prices respond immediately to new information and adapt correctly. According to this efficient-market hypothesis, anomalies or systematic patterns would not persist as investors would immediately exploit a deviation from the fundamental value. This prevailing theory of efficient markets has been increasingly criticized with the emergence of the behavioral finance. Since the 1980s, many scientific articles have been published, which refuted the efficient-market hypothesis and explained abnormal financial market effects with behavioral approaches. Nevertheless, there are many gaps in the literature, which I would like to fill with my research. On the one hand, I want to explore new markets in terms of their efficiency, such as the market for cryptocurrencies. On the other hand, I would like to analyze certain effects, which were hardly considered in the previous literature of behavioral finance (for example overreaction-effects, announcement-effects, size-effects and persistence-effects). This research is not only important to the review of the neoclassical theory, which is prevalent in economics. The results can also provide a significant basis for the evaluation of future regulatory decisions in the financial market.