Do Our Brains Determine Our Facebook Friend Count?

Guest Post by Ian Fyfe, originally posted on his own blog.

The amount of Facebook friends a person has correlates with the structure of brain regions involved in social interactions, according to research this week. But while this study made the top science news stories, looking a little closer reveals that it has not delved deeply enough into our online behaviour to really tell us anything.

The researchers took brain scans of volunteers and measured the volumes of certain brain regions that have previously been linked with social behaviour in humans. These measurements were then compared with individuals' answers to questions about their social life, including how many friends they have on social networking site Facebook.

They found that the volumes of some brain regions were bigger in individuals with more Facebook friends. However, the authors admit that they have not found a causal relationship that demonstrates larger brain regions to result in more Facebook friends, or vice versa. In fact, on closer examination, there is very little evidence that the correlation means anything at all.

One of the regions that correlated was the amygdala, a brain region involved primarily in emotion and emotional memory. Its volume has previously been shown to correlate with the size of an individual's ‘real world' social network, so the same result with Facebook is not groundbreaking; those with more ‘real' friends might be expected to have more online friends.

What the authors claim to be more interesting is the identification of three other brain areas whose volumes correlate only with online social network size and not with ‘real world' network size. Two of these regions, the right superior temporal sulcus (STS) and the left middle temporal gyrus (MTG), have been previously linked to social behaviour, and the third, the entorhinal cortex, is involved in memory, essential for keeping track of friends.

Neuroanatomy of Facebook Friends

The amygdala (left image) is deep inside the brain at the interface of emotional and memory systems. The entorhinal cortex (centre) overlays this on the inside, and feeds information into the memory systems.

The function of the middle temporal cortex (MTG) (central image, red) is unknown, but it has been linked several functions including face recognition and word meaning. The superior temporal sulcus (STS) is the tissue in the groove along the top of the MTG - this is thought to process biological motion and where others are looking.

However, examining what we know about the functions of these areas challenges their relevance to online social networking. The STS processes biological motion and the direction of another's gaze - socially important functions, but not easily related to making friends remote friends via a screen. Moreover, the exact function of the MTG is unknown, and although it's been implicated in face recognition, it has also been linked to understanding words while reading; a function more in line with web surfing than socialising. Finally, the entorhinal cortex functions in all kinds of memory, so is not specific to social behaviour. In light of this, the relevance of the correlation diminishes considerably.
On top of these dubious functional links, there are any number of confounding factors that cause variations in online social network sizes, as pointed out by Dr Heidi Johansen-Berg in her interview with the BBC: "Perhaps the number of Facebook friends you have is more strongly related to how much time you spend on the internet, how old you are, or what mobile phone you have," she said.

While the study did find a correlation between social network and ‘real world' network sizes, the average size of Facebook networks was more than three times the average number of phone book entries and over ten times greater than that of any other ‘real world' measure, leaving plenty of room for the influence of other factors.

The actual significance of this study seems to hinge on a question that it didn't even address: what does it actually mean to have more Facebook friends? It could mean that you are more sociable, as implicitly assumed in the study. But given that it indicates more time spent on the internet, it could also mean you are less sociable. It may be that you moved schools several times when young and have added your entire year-group from each school, or that you move jobs regularly. It could also mean you are more insecure or indiscriminate, more competitive or self-important. It could even mean that you add ‘friends' who have a nice picture, or have the same very common name as you.

In short, there is little to say that the size of your online social network has anything to do with how sociable you are. This issue needs to be clarified before any links are made between brain function and online friendship groups. Even then, uncertainty in brain region functions and confounding factors could still outweigh anything else and render the results of this study meaningless. It may be research that attracts the masses to the science news, but it is a long way from actually telling us anything useful.