Origins of the Theory

The six degrees of separation theory originated in 1967 when Harvard University professor Stanley Milgram conducted an innovative experiment by sending 300 identical letters with similar instructions across the United States. The letters were supposed to pass through specific social circles until they reached the designated recipient.

The experiment revealed a striking pattern: the paths that crossed and connected people in different parts of American society were surprisingly short, with the letters reaching the recipient in approximately six exchanges.

Over the decades since the experiment was conducted, numerous studies on the six degrees of separation theory, covering various topics from interactions with actors to friendships on social networks, have yielded similar results. These studies have shown that the average number of degrees separating any two people is six.

But the pressing question remained: why six? The answer was finally provided in a paper published in the journal Physical Review X. The authors of the study include researchers from Israel, Spain, Italy, Russia, Slovenia, and Chile.

Social Connections

In the course of the study, the team examined the dynamic equilibrium of human behavior, where a contradiction arises between the desire for social prominence and the associated costs of forming and maintaining social connections.

People naturally gravitate towards central roles in social networks, carefully selecting associations that advance them to these positions. However, any new relationships require time and energy, which places a significant burden on each connection," explain the authors of the study.

The study paints a picture of a network filled with nodes or 'rational agents' who are constantly evaluating the costs and benefits of their relationships with others. Each agent in this networked world is in a state of continual assessment, weighing the pros and cons of forming new connections and maintaining existing ones—all in an effort to enhance their own influence.

The results of the study show that social networks are a 'dynamic hive of individuals constantly playing a cost-benefit game, breaking connections on one hand and establishing new ones on the other.' 'This constant buzz is driven by the desire to occupy a central position in society. Ultimately, when this tug-of-war reaches equilibrium, everyone attains a position in the network that best balances their quest for prominence and their limited budget for new acquaintances,' according to the official press release of the study.

By conducting mathematical calculations, the authors of the study discovered a surprising result: this process always ends with social paths centered around the number six, which is quite remarkable. It's important to understand that each participant in the network acts independently, without any knowledge of this theory or intentions. Yet, this independent play shapes the structure of the entire chain, meaning we are dealing with a phenomenon of the recurring six degrees (or six steps) pattern.

Six Degrees of Kevin Bacon

Unknowingly, Hollywood actor Kevin Bacon made a significant contribution to the science and theory of six degrees of separation. It all started with an interview with Premiere magazine in 1994, where Bacon mentioned that the actors he worked with on the film "The River Wild" had worked with almost everyone in Hollywood. This initially obscure fact became the basis for a game created by three students who, during parties, discussed the number of films Bacon had been in and how many other actors he was connected to.

The students asked people to name actors and then searched for their connection to Bacon. As a result, they gained fame, appeared on late-night TV shows, and later co-authored a book with Kevin Bacon titled "Six Degrees of Kevin Bacon." Subsequently, Endless Games released a board game based on this concept.

Mathematical Proofs of the Six Degrees of Separation Theory

It is interesting to note that the six degrees of separation theory (and "Six Degrees of Kevin Bacon") has a mathematical foundation and numerous studies backing it up. One notable study is Stanley Milgram's "small world" experiment in 1973, where he used modeling with a fairly limited number of computers and predicted that there were approximately three degrees of separation between U.S. citizens.

Milgram's experiment, of course, has its limitations. However, the advent of social networks in recent decades and the subsequent connectivity to the Internet serve as proof of this phenomenon. By studying people's connections on Facebook and X (formerly Twitter), researchers obtained promising results. In 2011, Facebook's data science team published two papers stating that 99.91% of Facebook users are interconnected, forming a kind of chain.

Mathematicians have also tried to approach this idea from a scientific perspective: the people we want to connect can be seen as nodes, and their connections as chains. Then, considering the six degrees of separation theory, the maximum path length between two nodes should be six. The mathematical solution appears to provide a fairly reliable result.

Nevertheless, there are some important differences between using mathematics and the real world. For example, you can't just assume that the average person has 45 acquaintances, and there are also groups isolated from the rest of the world that are not taken into account. One way or another, the six degrees of separation theory is quite popular and will continue to be the subject of scientific research in the future. Meanwhile, we can draw the following conclusion: the world, after all, is small.