A cultural phenomenon, also known as the bandwagon effect, occurs when certain individuals behave a certain way merely because other individuals do as well. An example of a cultural phenomenon is the trend of sending flowers on Valentine's Day.
A cultural phenomenon also occurs when something or someone gains widespread popularity. This includes everything from films to musical artists to clothing styles. The thing that gains popularity is not a cultural phenomenon; rather, the cultural phenomenon is the process of something becoming popular. For example, Beyonce accumulating a large fan base is a cultural phenomenon. The theory is people are more prone to like something because other people like it.