TUESDAY, Jan. 7, 2014 (HealthDay News) — Although social networking sites let users keep in touch with a wide group of acquaintances, new research shows that people still put most of their efforts into communicating with a small group of friends or family members.

To maintain a manageable group of close contacts, people often institute an unconscious “one in, one out” rule, the study found. As friendships evolve or new friends are made, old friends may be cast out of the inner circle, the researchers said.

“Although social communication is now easier than ever, it seems that our capacity for maintaining emotionally close relationships is finite,” study author Felix Reed-Tsochas, a lecturer in complex systems at the Said Business School of the University of Oxford, in England, said in a university news release.

“While this number varies from person to person, what holds true in all cases is that at any point individuals are able to keep up close relationships with only a small number of people, so new friendships come at the expense of ‘relegating’ existing friends,” he said.

The study, published online Dec. 6 in the journal Proceedings of the National Academy of Sciences, involved survey data and mobile phone call records. The researchers used this information to identify changes in the communication networks of 24 students in the United Kingdom.

Over the course of the 18-month study, the students were transitioning from school to college or a job. When the study began, the researchers assessed the emotional closeness of each student’s network of friends and family. In each case, a small, close group of people was called much more often than anyone else.

Although the people in the participants’ social networks changed as they made a major life transition, they still made the same number of calls to the same number of people depending on their “emotional closeness” ranking, said Robin Dunbar, a professor of evolutionary psychology at Oxford.

“As new network members are added, some old network members are either replaced or receive fewer calls,” Dunbar said in the news release. “This is probably due to a combination of limited time available for communication and the great [mental] and emotional effort required to sustain close relationships.”

Even with the efficiency of devices such as cell phones, people’s communication patterns appear too deeply set to change, she said.

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