The number of Facebook friends that people have may be related to the size of brain regions involved in social interaction, research suggests.

In a study published in the journal Proceedings of the Royal Society B Biological Sciences, scientists looked at brain scans of 125 university students in London who were all active Facebook users and counted the number of  friends each had on the social network and in real life. 

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Some brain regions seem to link to the number of friends we have in both the 'real' and 'virtual' worlds. (Jonathan Ernst/Reuters)

The researchers found a link between the number of friends on the social networking site and the amount of grey matter in certain brain regions that have previously been implicated in social perception.

"We have found some interesting brain regions that seem to link to the number of friends we have — both 'real' and 'virtual,'" study author Dr. Ryota Kanai of University College London said.

"The exciting question now is whether these structures change over time —  this will help us answer the question of whether the internet is changing our brains."

The investigators cautioned it isn't possible to tell whether having more Facebook friends makes the regions of the brain larger or whether some people are "hard-wired" to have more friends.

"The relative contributions of 'nature' and 'nurture' therefore remain to be determined," the study's authors concluded.

In a series of experiments, the researchers found the volume of grey matter in the amygdala, a region associated with processing memory and emotional responses, was larger in people with a larger network of friends in the real world.

The size of three other regions were also tied with online social networks, but did not appear to be related with real-world networks:

  • Right superior temporal sulcus, which plays a role in our ability to perceive a moving object as biological. Structural defects in this region have been identified in some children with autism.
  • Left middle temporal gyrus, which has been shown to activate in response to the gaze of others and so is implicated in perception of social cues.
  • Right entorhinal cortex, which has been linked to memory and navigation — including navigating through online social networks.

In the study, volunteers were asked questions such as how many people they would invite to a party to estimate the number of their friends in the real world.

"We cannot escape the ubiquity of the internet and its impact on our lives, yet we understand little of its impact on the brain, which we know is plastic and can change over time," said Dr. John Williams, head of neuroscience and mental health at the Wellcome Trust, one of the funders of the study.

"This new study illustrates how well-designed investigations can help us begin to understand whether or not our brains are evolving as they adapt to the challenges posed by social media."

The study was also funded by the Japan Society for the Promotion of Science, the British Academy, the Danish National Research Foundation and the Danish Research Council for Culture and Communication, and the European Union MindBridge project.