How does social impact aggregate in a society?

Social sharing of emotions.
Cascade of social sharing from Rimé, 2009

Social impact does not happen in isolation because individuals influence each other. One example is influence cascades where social impact events trigger further social impact events. The figure shows an example of this kind of cascade described in 2009 by Bernard Rimé in his review about social sharing of emotions. One person experiences an emotion and tells their social contacts. Then those experience an emotion as result and they might express it to other contacts who might now know the first person reporting the emotion. This can happen further, for the case of emotions it has been documented up to three steps far.

The case of Twitter retweets is a similar one. We do not measure just how many of the followers of a user are influenced, but how many in total including followers of their followers and further down the follower network. The research question about predicting social media cascade sizes has been studied a lot and thus many different approaches exist. A 2017 essay by Jake Hofman, Amit Sharma, and Duncan Watts shows an example of various approaches and how this research question can serve as an example for testing the predictive power of social science theories.

Theory of fashion: the Simmel Effect

One of the first scientists to think about how influence aggregates at the collective level is Georg Simmel. Simmel is one of the fathers of sociology, especially with respect to the principles of social identity and social circles. Today we will focus on his work on fashion. Simmel defined fashion as the non-cumulative change in cultural features, where cultural features are displayed as status symbols. Status symbols are externally displayed traits associated with high social class, e.g. surnames, clothing, sport, food, etc. With these definitions in mind, Simmel observed this effect:

The Simmel effect: The persistence of social differences under the instability of status symbols

Simmel noticed that fashions come and go, but fashion is always present. When something becomes popular, it is bound to lose its popularity. Simmel introduced this theory in his 1904 article “Fashion”, describing observations that are still relevant, such as how going against fashion is a way to acknowledge its relevance (the hipster paradox). Simmel’s theory explains the emergence and instability of fashions based on two mechanisms: imitation and differentiation.