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Facebook and brain changes

Friday 21 October 2011

“Facebook users with more friends have bigger sections of brains,” the Daily Mirror reported. The newspaper said the study that made the finding did not reveal “if having more virtual friends makes the regions grow, or if such people are naturally ‘hard-wired’ to make more connections with others”.

This report is based on research that examined the associations between the size of a person’s online social network, the size of their real-world social groups and the structure of regions of their brain. An association was found between having more Facebook contacts, a higher number of real-world social contacts and the amount of grey matter in areas of the brain associated with social perception and memory.

This study measured the participants’ network size and brain structure at the same time. As such, it is unable to tell us whether there is a causal relationship between the two factors; that is to say, whether having larger social networks caused this part of the brain to grow or the other way around, or indeed whether some other factor causes both.

The study does not have any immediate practical implications in everyday life. In particular, it did not show that social networking has any specific effect on intelligence, social ability or any other cognitive, psychological or emotional abilities.

Where did the story come from?

The study was carried out by researchers from the University College London; Barts and the London School of Medicine and Dentistry, and Aarhus University in Denmark. It was supported by the Wellcome Trust; the Japan Society for the Promotion of Science; the Danish National Research Foundation; the Danish Research Council for Culture and Communication, and the European Union MindBridge project.

It was published in the peer-reviewed journal Proceedings of the Royal Society of Biological Science.

The media generally reported this study accurately. The Daily Mirror and the BBC appropriately pointed out that the study could only assess a link between the website and brain structures and not assess cause and effect. The Daily Mail, however, reported that, ‘brain scans showed it increases the size of the amygdala’, which is not correct as the study was not designed to find a causal relationship between the two.

What kind of research was this?

This cross-sectional study aimed to identify whether regions of the brain were associated with the size of a person’s online social network. The researchers’ theory was that the size of a person’s Facebook friend network would be reflected in the structure of brain regions involved in social behaviour. They also thought that the size of a person’s online network might be associated with the size of their real-world network.

A cross-sectional study measures two variables at one point in time. It can describe associations between these variables but cannot find the causal relationship between them. Thus, this study can describe links between network size and brain structure but cannot say whether the size of a person’s online network causes differences in brain structure, or whether people with different brain structures engage in different levels of online social activity.

What did the research involve?

The researchers recruited 125 university students to participate in the study. Their first experiment examined whether there was an association between variations in the number of social relationships on Facebook and variations in the structure of the brain. To assess this, each of the participants was asked how many Facebook friends they had and then given a brain scan using Magnetic Resonance Imaging (MRI). The researchers then investigated which regions of grey matter density demonstrated a positive correlation with the number of Facebook friends.

The second experiment involved 40 new participants. Their online social network size was measured and compared with the MRIs of three specific parts of the brain that were found in the previous experiment to be positively associated with online network size.

In the first two experiments, the researchers analysed the data in a manner that allowed them to control for the age, sex, and overall volume of grey matter. This was to ensure that these factors did not confound the relationship between network size and brain structure.

The third experiment examined the relationship between online networks and real-world social relationships. Eighty of the participants were asked to fill out a questionnaire that asked questions such as “If you were going to have a party now, how many people would you invite?”, ‘What is the total number of friends in your phonebook?’ and, ‘How many friends do you have from outside school or university?’

A final experiment examined the association between real-world social network size and the MRI results for 65 of the participants from the first experiment. The researchers focused on the size of the three regions that had been found to be positively associated with online network size, as well as the amygdala. When they analysed the data for this experiment, they controlled for the size of the person’s online social network in an attempt to reveal regions that were associated specifically with real-world social relationships.

What were the basic results?

In the first experiment, a significant positive correlation was found between the size of the participants’ Facebook friend networks and the density of grey matter in three specific brain regions (the left middle temporal gyrus, the right posterior superior temporal sulcus and the right entorhinal cortex). That is, the larger the Facebook network, the higher the grey matter density in these regions. There was also a weak association between online network and amygdala size.

The second experiment, which attempted to replicate the results of the first experiment in 40 new recruits, showed a significant association between online network size and grey matter density in the four brain regions described above. When the researchers controlled for the size of the person’s real-world network, however, the association with amygdala size became non-significant.

Experiment three revealed a positive association between the size of a person’s online social network and the size of their real-world network on five out of the eight measures of real-world network size, including:

  • the number of people in a person’s phonebook
  • the number they would invite to a party
  • the number of friends from outside school
  • the number of friends they would send a text message to in celebration of an event, and the number of friends they would ask a favour of

The final experiment showed that real-world social network size was positively associated with the size of the right amygdala, but not with any of the other regions found to be significant in the first experiment.

How did the researchers interpret the results?

The researchers conclude that three brain structures are positively associated specifically with online social network size, and that the right amygdala is associated specifically with real-world network size.

They conclude that, 'taken together, our findings demonstrate that the size of an individual’s online social network is closely linked to focal brain structure implicated in social cognition'.


This was a small cross-sectional study that investigated whether there was an association between involvement in online social networks and the size of brain structures in college students. The study is capable of showing there may be a relationship between the variables but cannot determine whether online social networking causes a change in the brains of people, or if larger brain structures cause a person to be more inclined towards forming large online social networks.

The study selectively looked at brain regions that were positively associated with network size, and did not seek to find regions that were negatively associated with online activity. As such, it probably does not provide a complete picture of the links between the two variables.

This was a small study, with the individual experiments often involving less than 100 people. It is difficult to draw conclusions from research involving such small groups, as chance is more likely to have influenced the results. The authors highlight some limitations of the study, including its focus on university students, and say that the research cannot describe the causal relationship between the variables. While the study did show that people with larger online social networks had larger brain structures in specific regions, it is unclear whether this has any functional impact. Further research would be needed to confirm the relationship between social networking behaviour and brain structures.

Assuming that this is a true relationship, it is unclear whether these findings have any practical medical application. The Daily Mail’s assertion that Facebook increased the size of the amygdala is incorrect.

Analysis by Bazian
Edited by NHS Website

Links to the headlines

Your Facebook friends are real after all… Number of contacts on the website linked to a person's social skills.

Daily Mail, 21 October 2011

Facebook users with more friends have bigger sections of brains.

Daily Mirror, 21 October 2011

Links to the science

Kanai R, Bahrami B, Roylance R, and Rees G.

Online social network size is reflected in human brain structure.

Proceedings of the Royal Society of Biological Sciences 2011, Published online before print October 19