We all have a unique social fingerprint, and no amount of Facebook or Snapchat can change that.

Researchers at the University of Oxford found that people have a “social signature” and maintain consistent communication patterns over time.

“Although social communication is now easier than ever, it seems that our capacity for maintaining emotionally close relationships is finite,” said Felix Reed-Tsochas, a lecturer at Oxford’s Said Business School. “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 that new friendships come at the expense of ‘relegating’ existing friends.”

Mobile technology and social networking sites make it easier to communicate with large numbers of acquaintances. Despite the proliferation of these services, people still put most of their effort into communicating with a small circle of close friends or relatives.

Basically, when you add someone to your inner circle, someone else gets the ax. And if you lose touch with one friend, another will soon take their place.

The study tracked changes in the communication networks of 24 students in the U.K. over the course of 18 months as they transitioned from school to university or work. It collected phone records and issued questionnaires.

In all cases, participants had a small, core group of people they most actively communicated with.

However, each participant also had a characteristic social signature that revealed their particular way of “allocating communication” across their network — even when they made new friends, they still made the same number of calls to people they were emotionally close to.

“As new network members are added, some old network members are either replaced or receive fewer calls,” said Robin Dunbar, a professor of evolutionary psychology at Oxford. “This is probably due to a combination of limited time available for communication and the great cognitive and emotional effort required to sustain close relationships. It seems that individuals’ patterns of communication are so prescribed that even the efficiencies provided by some forms of digital communication — in this case, mobile phones — are insufficient to alter them.”

There have been scores of studies on the various effects social media and mobile phones have on our relationships. The University of Michigan found last year that Facebook use “predicts declines in subjective well-being in young adults (makes them unhappy), and two German universities found that 1-in-3 people felt worse after visiting Facebook. 

One of the arguments for this phenomenon is that increases in the opportunities for and volume of communication have caused a decline in the quality of interactions.

Social network Path is built on “Dunbar’s number” (the same Dunbar quoted above), or the idea that people can only have substantial or stable relationships with a limited number of people at a time.

Dunbar’s research made big waves at the time, because it basically found that Facebook can’t really expand our social circle, even if we have 750 “friends.”

The research on social signatures, while it only worked with a very small group of students, underscores that idea. It may now be possible to interact on some level with thousands, even millions of people, but that doesn’t mean we should, or that communication like this enriches our lives in anyway.

Social networks serve a purpose, but that purpose is not to increase our capacity for close emotional relationships. That requires more old-fashioned methods.