When I heard about this, my heart sank. The Facebook area of the brain? It had all the hallmarks of a piece of media neuro-nonsense: a hook (Facebook!), a simplistic neo-phrenological story (bigger brains are better!)... so I was expecting to discover that the fuss was all about some tiny, statistically questionable study, which wasn't really about what the newspapers said it was, as is so often the case.People with lots of Facebook friends have denser grey matter in three regions of the brain, a study suggests
So I was very surprised to find that it's actually an extremely good paper.
Kanai et al from London took 125 young Facebookers (mostly students) and correlated their friend count with grey matter density across the brain. They found some correlations:
Most importantly, they included a replication sample, something that very few neuroscience papers do. After having done the first 125 people, they got another 40, and looked in the areas where they'd previously found results. They found the same correlation in all three cases - in fact, it was even stronger.
They even made sure to only display the scatterplots from the replication sample, thus avoiding the dreaded voodoo correlations problem that so often plagues such graphs. Note that the correlations are actually with the square root of the number of friends.
As if this wasn't enough, they confirmed a previously reported correlation between amygdala size and social network size, in both of their samples. And to cap it all, they show that Facebook friends are correlated (albeit not hugely) with other measures of number of friends.
So, as unlikely as it sounds, this Facebook finding is stronger than a good 90% of similar papers.
What does it mean that the size of the amygdala, left MTG, right STS and right entorhinal cortex are correlated with your Friend count? Good question. The authors discuss the result in terms of the known functions of these areas, e.g. the entorhinal cortex is involved in learning to associate pairs of stimuli, such as matching names to faces, which might be related to keeping track of your friends... but frankly this is just a post-hoc story.
You could tell an equally convincing tale about almost any part of the brain, if you found a correlation there. And as the authors point out, they didn't find correlations with other "social" areas you might expect like the mirror neuron system.
But that doesn't change the fact that the results of the study seem rock solid. So what's going on? It could be that having lots of friends makes your brain bigger. Or it could be the reverse, that having a certain kind of brain wins you friends, or at least Facebook ones. Or it could be that there's some third factor underlying the correlation, although who knows what that is.
Kanai, R., Bahrami, B., Roylance, R., & Rees, G. (2011). Online social network size is reflected in human brain structure Proceedings of the Royal Society B: Biological Sciences DOI: 10.1098/rspb.2011.1959
13 comments:
Yeah, when I finally got the paper, i also didn't find it as bad as I was prepared for. Good controls and everything, but it still doesn't seem to be entirely theoretically grounded.
I agree that the replication is an impressive feature of the study, and means we should take the result seriously.
But there is still something a bit odd here.
The authors start by discussing previous research linking social network size to amygdala volume. In their paper they report using the validated Social Network Size Questionnaire (SNSQ) in Experiment 3, which involved 80 participants from the UCL student community. They found that the nine questions (which included the key ‘Facebook’ question) loaded strongly onto a single factor. 65 of the 80 participants in Experiment 3 had been scanned in Experiment 1 or 2.
Now if this was me, the first thing I’d do would be to take a group of people and see how the single factor from the Social Network Size Questionnaire related to amygdala size, to see if I could replicate the Bickart study. We’ve already been told that this questionnaire has good factor structure, and any measure with several items will be more reliable than one with a single item. Furthermore, in Figure 3b we’re shown that the FB item has healthy correlations with nearly all the other questionnaire items. There doesn’t seem to be any justification, at least in the data presented here, for regarding the FB friends item as belonging to a separate scale. If, for instance, they’d presented a correlational analysis showing that internal consistency of the SNSQ improved after excluding the FB item, that would justify treating it separately.
Nevertheless, they pulled out the single Facebook item and focussed their analyses on that. Their reason for doing so was given as “It is sometimes anecdotally said the ‘friends’ acquired through online social networking are of a different character or number from those acquired through real-world social networks”. This appears to be a reference to Susan Greenfield, though she’s not cited - but they can’t be blamed for that since her views on this topic are relayed through the media rather than scientific outlets.
We don’t know if the original Bickart results would replicate if they whole SNSQ was used, as it’s not reported, but we do know that a measure of real-world network size (which presumably was based on the summed SNSQ excluding the Facebook item) was *not* significantly correlated with amygdala size (Results, Experiment 4, para 2).
Of course, if the authors had first found a null result for SNSQ and only then looked at correlations of individual items with brain measures, they would need to adjust their significance tests for the multiple comparisons. But their report suggests that, impelled by the Greenfield publicity, or some other source, they went directly to a study of Facebook friends as the first analysis they did, in which case the statistics seem fine. It’s not what I’d have done - I’d first have tried to replicate Bickart with a reliable multi-item measure - but that may reflect my pedestrian nature.
Thanks for the coverage and comments. To answer the question above, the reason for doing Experiment 3 was nothing to do with Susan Greenfield. Rather, it was that having done the study and replication, multiple journals rejected the paper with reviewers repeatedly claiming (with no evidence other than their own opinions) that although the methodology was sound, 'everybody knows that people don't have real friends on Facebook'. We got rather frustrated by this unscientific reviewing so did more experiments, with Bickart being published in the meanwhile.
Excellent Article, review and comments; seems to be an interesting researching point here. Thanks!
This reminds me the Dunbar number. Same correlation. Thanks for your post.
Geraint: Thanks for your response.
But it's not expt 3 that needs explanation, it's experiment 1, where you took a single behavioural measure, N facebook friends, as the phenotype to correlate with brain measures. What prompted you to do that? It's an unusual choice of measure if your main interest is in social networks.
It was surprising to hear that Bickart et al was published after studies 1-2 were completed and submitted for publication, as that study is given as a rationale for expts 1-2 and used to justify the region-of-interest analysis of the amygdala in those expts. I appreciate that the order of events in a scientific paper doesn't always need to follow the chronological order, but it is confusing for the reader, to put it mildly.
... and it could be that the process of "making friends", rather than having or being friends, grows these brain regions.
Statistically sound or not, studies like this are nonsense because they are of no use in developing models of brain function absent a causal relationship.
@deevybee;
I would have thought it was fairly obvious why one would choose 'n facebook friends' - any areas of significance are guaranteed media catnip, whereas reporting the SNSQ is likely to result in a worthy (but not newsworthy) publication. As we are all being pushed to demonstrate 'impact' and 'public engagement', this was a pretty sensible thing to do!
Geraint Rees wrote:
"... that although the methodology was sound, 'everybody knows that people don't have real friends on Facebook'. We got rather frustrated by this unscientific reviewing ..."
I am curious why are you calling this "unscientific reviewing"? It seems to me that the reviewer was objecting to a classification. Don't we want the classifications we make to have well understood operational definitions?
Friend is to Facebook as bullshit is to
a. gardening
b. reading
c. the speed of light
d. linoleum
tsisageya: Gardening, surely, cos just as you use friends to grow your Facebook, you use manure to grow your garden ;)
Neuroskeptic: Drat! Hoist with my own petard.
Based on my experience with people who have massive amounts of facebook friends, they tend to be high in the openness to experience. Also strongly extroverted.
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