« The trouble with community detection | Main | Power laws and all that jazz, redux »

November 06, 2009

Things to read while the simulator runs; part 8

While chatting with Jake Hofman the other day, he pointed me to some analysis by the Facebook Data Team about the way people use online social networks. One issue that seems to come up pretty regularly with Facebook is how many of your "friends" are "real" in some sense (for instance, this came up on a radio show this morning, and my wife routinely teases me for having nearly 400 "friends" on Facebook).

The answer, according to the Facebook Data Team, is that while it depends on how you define "real," with access to the underlying data, you can pretty clearly see how much interaction actually flows across the different links. One neat thing they found (within a lot of interesting analysis) is that the amount of interaction across all your connections scales up with the number of connections you have. That is, the more friends you have, the more friends you interact with. (It can't be a linear relationship, though, since otherwise, people with 1000s of friends would be spending all of their free time on Facebook... oh wait, some people actually do that.)

A related point that I've found myself discussing several times recently with my elders (some of whom I think are, at some level, alienated and befuddled by computer and Web technology), is whether Facebook (or, technology in general) increases social isolation, and thus is leading to some kind of collapse of civil society. I've argued passionately that it's human nature to be social and thus extremely unlikely that technology alone is having this effect, and that technology instead actually facilitates social interactions, allowing people to be even more social overall (even if they may spend slightly less time face-to-face) than before. Mobile phones are my favorite example of social facilitation, since they allow people to interact with their friends in situations when previously they could not (e.g., standing in line at the bank, walking around town, etc.), even if occasionally it leads to ridiculous situations like two people sitting next to each other, but each texting or talking on their phones with people elsewhere.

And, just in time to bolster my arguments, The Pew Internet and American Life Project released a study this week (also discussed in the NYTimes) showing that technology users are more social than non-technology users, and that other, non-technological trends are to blame for the apparent decrease in the size of (non-technology using) Americans' social circles over the past 20 years. Of course, access to and use of technology often correlates with affluence, so what really might be going on is that, like with nutrition, the affluent are better positioned to lead physically and socially healthy lives than the poor.

Recently, for a project on evolution, I've been reading pretty deeply in the paleontology and marine mammal literature (more on that in the next post). The first thing that I noticed is how easy it is now to access vast amounts of scientific literature from the comfort of your office. Occasionally, I had to get up to see Margaret, our librarian, but most of the time I could get what I needed through electronic access. But, sometimes I would encounter a pay wall that my institutional access wouldn't allow me to circumvent.

At first, it was extremely irritating and induced open-access revolutionary spirits in me. Then, I did what I suspect many of you have done, too, which is to ask my friends at other universities to try to get access to the paper using their institutional access, and to send me a copy. On a small scale, this is like asking your friends to share individual musical tracks with you. So, naturally, the logical solution to the problem is to make a P2P sharing system for scientific papers, right? Exactly. There's apparently already such a system for mainly medical papers, but I think the time is ripe for something more ambitious. Given what's been learned about how to run a good P2P system for music, it should be pretty simple to develop a good system (distributed, searchable, scalable) for sharing PDFs of journal papers, right? I can't wait until the academic publishing industry starts suing researchers for sharing papers...

If you're male, when you use a public restroom, what do you think about for those seconds while your body is busy but your mind is free to wander? Randall Munroe, of xkcd fame, apparently, thinks about the mathematics of restroom awkwardness and minimum awkward-ness packing arrangements for men using urinals. Who knew something so mundane could be so amusing?

Finally, this next bit is already almost a year old, but it's just so good. Remember last year when the media when predictably bonkers over two studies, by Nicholas Christakis and James Fowler, showing that happiness and obesity were (socially) contagious? That is, if you're depressed, you can blame your friends for not cheering you up, and if you're fat, you can blame your friends for making you eat poorly. (Or, wait, maybe it's that misery loves company...?) Shortly after those studies hit the media, a wonderful followup study was published by Cohen-Cole and Fletcher. Their study used the same techniques as Christakis and Fowler and showed that acne, headaches and height are also socially contagious! If only we had the data, I'm sure social network analysis could be show that hair color, IQ and wealth are socially contagious, too. Their concluding thoughts say it all, really:

There is a need for caution when attributing causality to correlations in health outcomes between friends using non-experimental data. Confounding is only one of many empirical challenges to estimating social network effects, but researchers do need to attempt to minimise its impact. Thus, while it will probably not be harmful for policy makers and clinicians to attempt to use social networks to spread the benefits of health interventions and information, the current evidence is not yet strong enough to suggest clear evidence based recommendations. There are many unanswered questions and avenues for future research, including use of more robust empirical methods to assess social network effects, crafting and implementing additional empirical solutions to the many difficulties with this research, and further understanding of how social networks are formed and operate.

E. Cohen-Cole and J. M. Fletcher, "Detecting implausible social network effects in acne, height, and headaches: longitudinal analysis." BMJ 337, a2533 (2008).

Update 10 Nov.: Oh jeez. Olivia Judson, please get a clue.

posted November 6, 2009 08:19 AM in Things to Read | permalink


Didn't Barabassi (of Linked) write that the interaction increases as the square of the size of the network or something? :P

Posted by: df at November 6, 2009 11:18 PM

Wow, all of this in one entry. :)

For (1), it's worth remarking that interaction frequency with a Facebook friend in some cases is (or is at least expected to be) rather different from interaction frequency in real life. For example, roommates might be very close friends and ideally could talk to each other for many things that might otherwise be shared online. The usual node heterogeneity (well, usual from real life if not from models!) comes into play as well.

The article you mention in (5) is definitely highly amusing. According to Christakis and Fowler, there's apparently been an ongoing discussion (battle?) with those other authors. Even amidst the massive press they've gotten, many of the popular articles have actually included similar cautionary comments from other social scientists. Granted, I prefer the mathematics culture that tends to more often lead to underselling instead of overselling. (At perhaps its most extreme: A couple of times, I have seen a professor give a math seminar without mentioning any fanfare only to find out later from local faculty that the proof presented so casually in it turned out to be the solution to a very hard 100+ year old problem.)

Posted by: Mason Porter at November 7, 2009 05:40 PM

Somehow, it seems more scientific to err on the side of underselling a result, perhaps because that kind of detachment suggests that you have no personal stake in the correctness or incorrectness of what you say. To me, scientists like Christakis and Fowler, by talking up (bragging about) their work and by failing to seriously consider how they could be wrong, do a disservice to science by treading too close (for my comfort) to the kind of mistakes and hubris that brought us episodes like polywater and cold fusion. In some sense, it's a kind of marketing-ization of science, and it spoils the objectivity that separates science from things like punditry and politics. (Of course, the self-correcting nature of science, with Cohen-Cole and Fletcher's article being exemplary, is one of its best attributes. But sadly, the corrective studies rarely get the same kind of attention that provocative but ultimately flawed studies do...)

On a related point, it never ceases to irritate me that complex systems seems to have more than its fair share of people who appear to, for whatever reason, care less than I would like about being scientifically careful. Older fields seem to have less of this kind of behavior... maybe because the barriers to entry are higher and because progress less ambiguous? Here's something I struggle with: what's the right balance between being open vs. closed to unconventional ideas, some of which will be fundamentally novel and correct, but some of which will be wrong, flawed or worse? Surely part of the answer is to force scientists to do certain kinds of things before they get published, and part of it is to let the self-correction sort things out. But, I think it's a hard mix to get right, and I don't think complex systems is close to a sweet spot yet. (And, I'm not sure the structural problems with the scientific publication process do much to help find this balance; if anything, current trends may be making it worse!)

Whoops. Somehow this turned into a rant...

Posted by: Aaron at November 7, 2009 10:27 PM

I prefer underselling as well, though there is a rather unfortunate pressure against that to be able to get jobs, etc. I consciously attempted to get a job in a math department as opposed to, say, a physics department in large part because of such cultural issues. And I am far from the only person between mathematics and other disciplines who has gone through great pains to try to make this happen...

Complex systems definitely has more of this than other fields. That's what makes it (rightfully) a dirty word among many scientists. There are even dirtier words, but all of the prevailing crap requires me to defend my own work more than I would otherwise have to. (I was asked at my Oxford interview---almost in these terms---whether I think the study of complex systems and networks is truly science. Having debated that with myself and others at various points, I had a good, well-thought-out answer to the question. But the point is that one can't even imagine such a question being considered legitimate in many other situations, and such legitimacy is a byproduct of all of the crap.)

I agree that they tend to oversell their work. I should be careful what I write, though, as I have written papers with Fowler. ;) However, I believe that in those papers we have been careful to be reasonable.

It is more scientific to undersell. It's just harder to get grants and good jobs that way. Therein lies much of the problem...

I'm not sure how much of this literature you've read, but if you want to see overselling, take a look at the date/party hub literature. Sheesh.

Posted by: Mason Porter at November 8, 2009 08:48 AM