IntroductionSocial psychology is a part of psychology that studies human behavior in society. Overall, this section of science is one of the most useful parts of psychology. People need to know which variables influence their behavior and change them if they are not appropriate. In my essay I discuss three theories of social psychology such as: fundamental attribution error, cognitive dissonance and obedience to authority. Fundamental attribution error The fundamental attribution error is one of the theories of social psychology. This error explains the inappropriate judgment of other individuals (Wortman & Loftus, 1992). People prefer to describe the behavior of others based on their internal strength without thinking about external reasons. Usually people do not know many factors that can influence someone and would like to draw a conclusion first based on stereotypes or other experiences. There may be two stages of fundamental attribution error. The first is to make quick reasoning about someone's behavior based on their personality. If the person sees an error in judgment, he or she can move to the next level of analysis. The second phase is to understand more deeply and accurately the reasons for the behavior of others. Due to this long process, people do not consider the second phase as a necessity. One of my personal experiences of fundamental attribution error occurred in Prague. One of my friends arrived late to meet me early in the morning and I had the opinion that this person was not punctual and was lazy in getting dressed earlier. A week later I was late to a different meeting with exactly the same friend, but I tried to explain my lateness with other reasons; as if my tram was broken. After that, I asked for…half of the paper…and better muscle contraction. We cut off the frogs' legs to see how they move. I didn't want to follow these instructions because it was very brutal for me and I felt sorry for the animals. My teacher repeated that I had to do this experiment to receive additional points for my grade. Even though I didn't want to cause any pain to the frog, I did this experiment. Obedience to authority can explain many bad decisions in human history. For me it is more fear of being punished by the authorities than being afraid of this person. It is more appropriate for people who know their authority to use it to inspire and support someone's ideas and behavior. Conclusion In my opinion, the most powerful theory is cognitive dissonance as it affects our mental state. Thanks to my research, social psychology can be very effective in studying and changing human behavior.