What do the Spice Girls, the Power Rangers and the starting lineup of the 1996 Chicago Bulls all have in common? Aside from the fact that they dominated the action figure market of the mid-'90s, they also all perfectly exemplify the so-called social brain hypothesis, which holds that humans are capable of maintaining close relationships with no more than five people. According to a new study in the journal arXiv, this rule may apply not only to superstar quintets, but to entire populations.
Initially suggested way back in the 1970s, the basic premise of this theory is that primate brains developed to a certain size in order to be able to handle the stresses of living in large social groups, in which a wide number of personal relationships are required. However, since the closest of these relationships usually come with a lot of emotional baggage, it’s only possible to develop a limited number of truly intimate connections, while the rest of our peers take a back seat as mere acquaintances.
Based on this concept, analyses of Facebook and Twitter data over recent years have enabled researchers to come up with a model for human social networks, made up of four “Dunbar layers”. According to this model, the innermost layer, which represents a person’s closest contacts, has an average of five other people in it. Successive layers then contain increasing numbers of contacts, but with a decreasing level of “emotional closeness,” reaching a total of 150 people in a typical social network.
The Jackson Five were a perfect example of the social brain in action. CBS Television via Wikimedia Commons
To test the robustness of this concept, a team of researchers – including Robin Dunbar, who initially came up with the model – analyzed every cell phone call made in an undisclosed European country during the year 2007. Working on the premise that the number of calls between any two people indicates the closeness of their relationship, they sought to determine if these Dunbar layers could be observed in the data.
Results showed that not only was it possible to identify these layers in these telephonic interactions, but that the number of contacts in these layers was remarkably similar to that proposed by previous studies. For instance, people were found to have an average of 4.1 extremely close friends, who they called much more regularly than their other relations. Three further layers of increasingly numerous yet distant contacts were then detected, with the average number of people in a given individual’s entire social network being 128.9.
Commenting on these findings, the study authors suggest that the Dunbar model does indeed appear to hold water as an accurate representation of human social relationships. However, they also admit that “we still do not have any principled explanation for why these structural layers should have such a consistent pattern.”
Regardless, the study seems to confirm that when it comes to forming the perfect group, five really is the perfect number, which could explain the success of the likes of the Famous Five, One Direction, and the Teenage Mutant Ninja Turtles (if you include Splinter, of course). Hollywood scriptwriters looking for ideas for upcoming movies may also want to use the following suggestions: The Five Musketeers, Five Dalmatians, and a sequel to the film "300"… 5.