The Physics of Friendship

March 10, 2006 feature
The Physics of Friendship
In this visualization of a high school’s empirical friendship network from the scientists’ data, the different colored (blue, green, purple, orange) nodes represent students in different grades. Links between nodes are drawn when a student nominates another student as a friend. In the recent study, physicists developed a novel model to describe this social network based on rules governing physical systems. Credit: Marta Gonzalez

By comparing people to mobile particles randomly bouncing off each other, scientists have developed a new model for social networks. The model fits with empirical data to naturally reproduce the community structure, clustering and evolution of general acquaintances and even sexual contacts.

Applying a mathematical model to the social dynamics of people presents difficulties not involved with more physical – and perhaps more rational – applications. The many factors that influence an individual’s fate to meet an acquaintance and decide to become a friend are impossible to capture, but physicists have used techniques from physical systems to model social networks with near precision.

By modeling people’s interactions based on how particles bounce off each other in an enclosed area, physicists Marta Gonzalez, Pedro Lind and Hans Herrmann found that the characteristics of social networks emerge “in a very natural way.” In a study recently published in Physical Review Letters, the scientists compared their model to empirical data taken from a survey of more than 90,000 U.S. students regarding friendships, and found similarities indicating that this model may serve as a novel approach for understanding social networks.

“The idea behind our model, though simple, is different from the usual paradigmatic approaches,” Gonzalez told PhysOrg.com. “We consider a system of mobile agents (students), which at the beginning have no acquaintances; by moving in a continuous space they collide with each other, forming their friendships.”

After a collision, a particle moves in a different direction with an updated velocity, just as how an individual’s chance of meeting a new person depends on their most recent acquaintances.

At a critical point, the system reaches a quasi-stationary state, for the first time allowing the scientists to reproduce several features of social networks in a single model and in a natural way. Specifically, this technique accurately describes social clustering, the way friendships evolve over time, the shortest path length in a large group, and some features related to group structure.

“With this new framework, we show that specific velocity and collision rules are able to reproduce the statistical and structural features of empirical social networks,” said Gonzalez. ”Therefore, this model seems to have the novelty of bringing together all the previous developments for collision theory with the empirical results of socio-dynamics.”

The scientists were also able to apply this model to describe specific types of contacts to produce a distribution that again closely resembles real-life acquaintances. For example, to separate sexual contacts from all social contacts, the scientists assigned to the sexual contacts an intrinsic property that could then be used to model these distinct networks. In this case, the model reproduced the real sexual contact network found in a tracing study of HIV tests.

Although this particle motion does not literally model human motion, it represents connections among people – and it’s these links that contain the most significance for social networking theories. For example, links can represent the flow of information traveling through a community. By knowing the shortest path, communicators can optimize the information flow and improve productivity in a business. With the ability to determine hot hubs or holes in a community, business managers can identify leaders or points that require an organizational change.

As Gonzalez sees it, statistical physics and human behavioral studies have a history of inspiring each other, which makes physicists’ desire to understand social networks a natural interest.

“As Philip Ball [Nature Editor] remarks,” said Gonzalez, “‘by seeking to uncover the rules of collective human activities, today's statistical physicists are aiming to return to their roots: Social statistics also guided Maxwell and Boltzmann towards the utilization of probability distributions in the development of the kinetic theory of gases – the foundation of statistical mechanics’ (Physica A 314 (2002) 1-4)."

Citation: Gonzalez, Marta C., Lind, Pedro G. and Herrmann, Hans J. System of Mobile Agents to Model Social Networks. Physical Review Letters. 96, 088702 (2006).

By Lisa Zyga, Copyright 2006 PhysOrg.com

Explore further: Uber's problems highlight silicon valley's faltering vision for the future

Related Stories

Inflight internet ready to take off

June 22, 2017

Inflight internet access, a nascent market still hobbled by slow speeds, is set to take off as dedicated satellites make surfing in the skies a reality, experts say.

New study maps out core concepts in the vaccination debate

June 23, 2017

The recent measles outbreak in Minnesota — by June, new cases of the disease in that state surpassed nationwide totals for all of 2016 — has been a sobering reminder of how highly concentrated populations of vaccination ...

Faster performance evaluation of super-graphs

June 19, 2017

Himchan Park and Min-Soo Kim of DGIST have developed TrillionG, a computer model that generates synthetic data for simulating real-world applications that use giant graphs. TrillionG is faster than currently available synthetic ...

How legalising cannabis can help society

June 21, 2017

Leading drug researcher Associate Professor Chris Wilkins from Massey University's SHORE and Whāriki Research Centre is calling for the adoption of a not-for-profit public health model for recreational cannabis. It would ...

Recommended for you

Tiny magnetic tremors unlock exotic superconductivity

June 26, 2017

Deep within solids, individual electrons zip around on a nanoscale highway paved with atoms. For the most part, these electrons avoid one another, kept in separate lanes by their mutual repulsion. But vibrations in the atomic ...

More than meets the eye to ulcer-inducing bacterial protein

June 26, 2017

Scientists at The University of Western Australia and Perth-based biotech Ondek Pty Ltd have revealed new insights into the function of an important bacterial protein in Helicobacter pylori, the bacterium that causes stomach ...

Artificial brain helps Gaia catch speeding stars

June 26, 2017

With the help of software that mimics a human brain, ESA's Gaia satellite spotted six stars zipping at high speed from the centre of our galaxy to its outskirts. This could provide key information about some of the most obscure ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

QubitTamer
1 / 5 (1) Aug 06, 2009
clear proof that kids today have no idea of what friendship is...social media contacts have replaced buddies you play sports with after school and on weekends...this is why kids today are fatter and more narcisistic than ever...

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.