If you have ever wandered why people do certain things, and why people do not do certain things, social psychology has an explanation to it. If you have ever been completely struck by the atrocities that occur and people do not report, there is an explanation for it through social psychology. On March 13, 1964, a woman named Kitty Genovese was murdered in New York City. What was shocking to most people was the fact that there were several witness and very few, in fact none did something about the murdering. What exactly was the cause of this phenomenon? No one was completely sure about it; Because of this, psychological experiments were set out to figure out the cause. What was discovered, was later known as the bystander effect. The bystander effect is a phenomenon that happens when people see something, potentially bad, happening such as someone being beaten, someone being shot, someone being killed, or even someone in pain, and they do not offer help or any type of assistance. What is interesting about the bystander effect is that the more people, or bystanders that are around, the less people are going to be willing to offer help. What this was identified as later, is a diffusion of responsibility. The responsibilities that someone has to help people are diffused among all of the people. Above, and on a link in this page, there is a video of an example of this.
If you have ever been in a game of tug-of-war, you have experienced something that psychologists call social loafing. Social loafing is when there is a lot of people around, people are likely to exert less amount of force to achieve the same results. A psychology experiment that blindfolded people and either told them that they were in a group of different people tugging on a rope, or tugging on a rope by themselves. The people that were told that they were with a group tugging, all exerted less amount of force. This also happens in groups and projects where one will put less time and effort, only because they know that there are other people in the same group.
Something that happens often between groups is groupthink. If you have ever been in a group and realize that as things are being discussed, you tend to favor and "accept" other theories and topics given to you, only for the reason of not getting into an argument, you are going through what psychologists call group think.
Another thing that social psychology explains is something they call social facilitation. If you remember being a child trying to learn how to do something new and you felt accomplished that you had learned it, you always wanted to show someone else. When you showed someone what you had learned to do, you would get excited and completely fail at the task that you were trying to do. This is what social facilitation is; the tendency to do complicated tasks WORSE in front of people and to do simple tasks BETTER in front of people. Social psychology is one of those topics of psychology that explain all the little mysteries that people have had since they were little. It is an evolving part of psychology and in the future, it will possibly, explain a lot more.