Rumors are stories that can be true, false or somewhere in between. They can have a huge impact on the way people think and act, whether it is about how they should dress for an event or whether they should buy a product that might cause cancer.
While some rumors are harmless, others can cause massive economic harm or even lead to catastrophe. It is important to understand why and how a rumor becomes so powerful that it can affect our everyday decisions.
When a rumor is disseminated it goes through four stages: 1) emergence (the rumor is first shared by someone); 2) confirmation (the rumor is subsequently confirmed as true or false); 3) replication (the rumor is repeated by other individuals); and 4) reinforcement (the rumor is believed over and over again).
The origin of the word rumor can be traced back to Latin, where it is used to describe any noise that cannot be identified or defined. The word has evolved through the centuries to mean anything that is spread without proof or authority, including a story told among friends or family members, an urban legend or even an unsubstantiated report in the media. In the modern day, rumor has become an extremely common form of communication and can be accessed and distributed in a variety of ways through social media and mass channels.
Although a rumor can be true, it is often difficult to determine its truth. Many rumors are never verified, such as when a student overhears students talking about getting out early from school before the administration officially announces the move. Others can be backed up by evidence, such as pictures, a statement from an authority figure or a link to a website that provides more information about the issue at hand.
Evidence is key to the success of a rumor, but it can be difficult to determine what constitutes valid evidence. Some rumors are more likely to be believed if they have a familiar source or if the person spreading the rumor has a high degree of social capital (e.g., being a recognized expert in the field). However, it is also possible for a rumor to gain traction simply because it is controversial or disturbing.
There are a number of factors that influence the likelihood of a rumor to be spread, such as anxiety (both personality and situational); ambiguity; and importance of information. Anxious individuals are more likely to create a rumor in an attempt to lift their own anxieties, while ambiguous and unpleasant information can spark a rumor that may not be based on fact.
To better understand the nature of a rumor, researchers have looked at how people respond to them in online social networks. For example, Friggeri et al.  studied how people respond to rumors by examining tweets that include links to the web page Snopes, which fact-checks information. They found that when a rumor is verified as true, there is a sharp increase in messages denying it, while this does not happen with unverified false rumors.