The scientific study of how people's thoughts, feeling, and actions are affected by others is called psychology.

The correct answer would be : Social Psychology

Basically, social psychology analyze human's behavior as a social animal. Example of subjects that covered in social psychology :
- What is the characteristic that most people perceive as suitable for leadership ?
- How will the point of view of other people affected another people's point of view in a group ?
- Is a single individual's mood could affect the mood of other people in the group and visa versa ?