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Number of Facebook friends linked to brain structure

Oct. 18, 2011
Courtesy of the Wellcome Trust
and World Science staff

There’s a link be­tween the num­ber of “Face­book friends” a per­son has and the size of cer­tain brain re­gions, as well as their num­ber of real-world friends, sci­en­tists have found. But it’s un­known, they say, wheth­er hav­ing more Face­book friends makes those brain re­gions larg­er, or wheth­er it works the oth­er way around.

The so­cial net­work­ing web­site Face­book, de­signed to let peo­ple stay in tou­ch with net­works of friends on­line, has more than 800 mil­lion ac­tive users world­wide. Some have only a hand­ful of on­line friends, oth­ers over a thou­sand. “On­line so­cial net­works are mas­sively in­flu­en­tial, yet we un­der­stand very lit­tle about the im­pact they have on our brains. This has led to a lot of un­sup­ported specula­t­ion the In­ter­net is some­how bad for us,” said re­search­er Ge­raint Rees of Uni­vers­ity Col­lege Lon­don.

Rees and col­leagues stud­ied brain scans of 125 uni­vers­ity stu­dents who were ac­tive Face­book users and com­pared them to the size of the stu­dents’ net­work of friends, both on­line and in real life. Their find­ings, which they rep­li­cat­ed in a fur­ther group of 40 stu­dents, are pub­lished Oct. 18 in the jour­nal Pro­ceed­ings of the Roy­al So­ci­e­ty B.

The in­ves­ti­ga­tors re­ported a strong link be­tween num­ber of Face­book friends and amount of “grey mat­ter”— the brain tis­sue where men­tal pro­cess­ing is be­lieved to take place—in sev­er­al brain ar­eas. One is the amyg­da­la, which is as­so­ci­at­ed with pro­cess­ing mem­o­ry and emo­tion­al re­sponses. Oth­er re­search has found that there is more grey mat­ter in this ar­ea in peo­ple with more real-world friends, so the Face­book work showed the same goes for on­line pals, Rees’ group re­ported.

The size of three oth­er re­gions – the right su­pe­ri­or tem­po­ral sul­cus, the left mid­dle tem­po­ral gy­rus and the right en­torhi­nal cor­tex – al­so cor­re­lat­ed with on­line so­cial net­works, but not with real-world net­works, the study found. The su­pe­ri­or tem­po­ral sul­cus 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. The en­torhi­nal cor­tex, mean­while, has been linked to mem­o­ry and naviga­t­ion – in­clud­ing nav­i­gat­ing through on­line so­cial net­works. Fi­nal­ly, the mid­dle tem­po­ral gy­rus has been shown to ac­ti­vate in re­sponse to the gaze of oth­ers and so is im­pli­cat­ed in per­cep­tion of so­cial cues.

“The ex­cit­ing ques­tion now is wheth­er these struc­tures change over time,” which should help re­veal “wheth­er the In­ter­net is chang­ing our brains,” said Ry­ota Kanai, one of the re­search­ers. 

To learn the rela­t­ion­ship be­tween the size of a per­son’s on­line net­work of friends and their real-world net­work, the re­search­ers asked their vol­un­teers ques­tions such as “How many peo­ple would you send a text mes­sage to mark­ing a cel­e­bra­to­ry event (e.g. birth­day, new job, etc.)?”, “What is the to­tal num­ber of friends in your phone­book?” and “How many friends have you kept from school and uni­vers­ity that you could have a friendly con­versa­t­ion with now?”

“Our find­ings sup­port the idea that most Face­book users use the site to sup­port their ex­ist­ing so­cial rela­t­ion­ships, main­tain­ing or re­in­forc­ing these friend­ships, rath­er than just cre­at­ing net­works of en­tirely new, vir­tu­al friends,” said Rees.

“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 [flex­i­ble] and can change over time,” said John Wil­liams, head of neu­ro­sci­ence and men­tal health at the Lon­don-based Well­come Trust, which funded the re­search. “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.”


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There’s a link between the number of “Facebook friends” a person has and the size of certain brain regions, as well as their number of real-world friends, scientists have found. But it’s unknown, they say, whether having more Facebook friends makes those brain regions larger, or whether it works the other way around. The social networking website Facebook, designed to let people stay in touch with networks of friends online, has more than 800 million active users worldwide. Some have only a handful of online friends, others over a thousand. “Online social networks are massively influential, yet we understand very little about the impact they have on our brains. This has led to a lot of unsupported speculation the Internet is somehow bad for us,” said researcher Geraint Rees of University College London. Rees and colleagues studied brain scans of 125 university students who were active Facebook users and compared them to the size of the students’ network of friends, both online and in real life. Their findings, which they replicated in a further group of 40 students, are published Oct. 18 in the journal Proceedings of the Royal Society B. The investigators reported a strong link between number of Facebook friends and amount of “grey matter”— the brain tissue where mental processing is believed to take place—in several brain areas. One is the amygdala, which is associated with processing memory and emotional responses. Other research has found that there is more grey matter in this area in people with more real-world friends, so the Facebook work showed the same goes for online pals, Rees’ group reported. The size of three other regions – the right superior temporal sulcus, the left middle temporal gyrus and the right entorhinal cortex – also correlated with online social networks, but not with real-world networks, the study found. The superior temporal sulcus 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. The entorhinal cortex, meanwhile, has been linked to memory and navigation – including navigating through online social networks. Finally, the middle temporal gyrus has been shown to activate in response to the gaze of others and so is implicated in perception of social cues. “We have found some interesting brain regions that seem to link to the number of friends we have – both ‘real’ and ‘virtual’. 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,” said Ryota Kanai, one of the researchers. To learn the relationship between the size of a person’s online network of friends and their real world network, the researchers asked their volunteers questions such as “How many people would you send a text message to marking a celebratory event (e.g. Birthday, new job, etc.)?”, “What is the total number of friends in your phonebook?” and “How many friends have you kept from school and university that you could have a friendly conversation with now?” “Our findings support the idea that most Facebook users use the site to support their existing social relationships, maintaining or reinforcing these friendships, rather than just creating networks of entirely new, virtual friends,” adds Professor Rees. “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 [flexible] and can change over time,” said John Williams, head of neuroscience and mental health at the London-based Wellcome Trust, which funded the research. “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.”