Connections in social networks display a number of characteristics, such as homophily, multiplexity, and triadic closure, that can provide researchers with valuable insights into collective action.
Homophily is the tendency of social entities to associate with others that are similar to them in some way. In a 1954 study, sociologists Paul Lazarsfeld and Robert Merton identified two primary forms.
The first type is referred to as status homophily, suggesting that individuals of the same age, race, religion, occupation, or wealth, to name a few possibilities, are more likely to be in a relationship than individuals who do not share that characteristic. The second type is called value homophily, recognizing that it is also likely that individuals who share similar thoughts or values, such as political views, love of animals, taste in music, or favorite cuisines, among other things, are again more likely to form relationships. A common explanation for homophily is that, in the absence of adequate exposure to alternatives, we go with what we know. In a recent book (2012), sociologist Dhiraj Murthy points out that despite Twitter’s ability to easily connect individuals with widely differing thoughts and values, the majority of people still tend to follow others who share views similar to their own.
Multiplexity refers to the fact that the relationships between nodes in a network can be based on more than one criterion. At an individual level, for example, it is not uncommon for two people to be friends, co-workers, members of the same sports team, neighbors, and so on. At the level of the corporation, some recent research has examined the supplier-customer relationship in the business-to-business environment, to determine the effect of multiplexity on sales volume and sales volatility. Findings suggest that, in cases where the suppliers and customers share research and developments efforts, engage in mutual marketing campaigns, enter licensing agreements, or share information technology, for example, the supplier enjoys an increase in sales and a decrease in sales volatility.
The notion of triadic closure was originally developed in the work of sociologist Georg Simmel. He suggested that if John was friends with George, and John was also friends with Bill, then John would exert some amount of effort to ensure that George became friends with Bill, thus closing the network they form. Researchers use the term transitivity to refer to the assumption made by John that, based on his friendship with both George and Bill, it makes sense that they should also be friends. Even though this phenomenon is described in terms of networks with three nodes, it has proven important for understanding the way that networks evolve. Tightly-knit networks often emerge as an extension of triadic relationships, while loosely-coupled networks tend to exhibit less triadic closure among their nodes.
The next article in the series will deal with ways that nodes and ties are distributed in a network.