Despite the growing use and impact of social media, the closer you live to another person, the more likely you are to be friends with them.
This is according to a new study that drew on data from the location-based social network provider Gowalla.
The study, by researchers within the Social Cognitive Network Academic Research Center (SCNARC) at Rensselaer Polytechnic Institute, also showed that people tend to move in groups of friends, and that two people chosen at random at a specific event (like a concert or at a particular store) are unlikely to be friends.
While the findings are seemingly common-sense, the study, and continued research on social networks, holds a powerful message for a broad range of applications that rely on accurate predictions of how people move, such as emergency planning, infrastructure development, communications networks, and disease control.
"The ramifications are extremely important because if we assume that people are moving randomly, we are wrong, and therefore we will not be prepared for what people actually do," Boleslaw Szymanski, director of SCNARC and the Claire and Roland Schmitt Distinguished Professor of Computer Science at Rensselaer, said.
"Where you live really matters: Most of your friends are concentrated in the place where you live, and as the distance increases, this concentration rapidly drops," Szymanski added.
The findings also indicate that, even in the digital age, humans still form friendships based on personal interactions, Tommy Nguyen, a Rensselaer graduate student and member of SCNARC, said.
"Even though, thanks to the Internet, you can be friends with anyone on the planet, the likelihood that a person will be friends with someone in a distant location chosen at random is far lower than the likelihood that this person will be friends with someone who lives in close proximity," Nguyen said.
"Proximity creates a strong boundary for who will be your friends," he added.
The study, titled "Using Location-Based Social Networks to Validate Human Mobility and Relationships Models," was awarded the best paper award at the Second Workshop on Social Network Analysis in Applications held earlier this year in Istanbul, Turkey.
Researchers found that 80 percent of friends of a particular person live within 600 miles of that person's home.
"You may have a few distant friends who are holdovers from a time when you lived elsewhere, or who share a common trait like family connections or a particular activity, but in general, the likelihood of friendship decreases as distance increases," Szymanski said.
"That tells us an important thing which our findings highlight: Friendship requires constant interactions, maybe physical presence (making proximity important) because we prefer to rely on verbal and body language to invoke feelings of trust in people. That's very important in friendship," he added.