Tuesday, May 5, 2009

Smart Social Networks (consult a health professional before reading)

Different social networks have different properties with respect to transmission of information. Physicists have studied these sorts of networks in a variety of contexts- the problems of electronic conduction in random media and oil propagation in porous rock are deeply connected to the problems of virus transmission between people or between computers, for that matter.

A phenomenon that occurs in many of these networks is that propagation through the network can depend exponentially on parameters such as connection strength, connectedness of nodes, dimensionality of the network, etc. To use twitter as an example, a link might propagate to ten times as many people if the retweet rate changes by 10% (numbers completely fabricated). Or it might be that Macs are a million times less likely to be infected by a virus even because they are only 10 times less likely to retransmit a virus. (the product of a factor of 5 lower density and a factor of 2 intrinsic security (numbers that might not be true, but should be)).

I've been thinking a lot recently about propagation on networks this past week because of the news on influenza A (H1N1) AKA swine flu. You see, I got back from a week's vacation in Mexico a week ago, and I was just amazed at the break-out of flu hysteria. The amount of sheer stupidity out there is just appalling. I am reminded of Ionesco's Rhinocéros when I hear how common sense has also taken a vacation and gotten the flu. It's particularly striking when raw prejudice is accepted by otherwise rational people as prudence. One of many amazing bits of non-thought that I've heard or seen this past week: Perfectly healthy Students at Slippery Rock State University who went to Mexico are being prevented from attending graduation.

Lost in this are many shreds of rationality: Let's suppose a pandemic is really going to happen. That means that all of us will get exposed sooner or later. From the public health point of view, the spread needs to be slowed sufficiently that public health resources can be marshalled in plenty of time. But from the individual point of view, however, the worst thing for you is to contract the disease at the peak of the pandemic, when society's resources are most strained. There are two ways to avoid this- one is to become a hermit and hope you are not exposed until after the peak. The other is to contract the disease early, before the public health system comes under strain (making sure not to give it to anyone else). It's just the flu!

Maybe part of the reason for hysteria is that people don't understand the exponentials I mentioned above. When confronted with a potentially deadly pandemic, it's hard to imagine that something as simple as washing your hands could stop the scary monster in its tracks. You know intuitively that washing your hands will only protect you a little bit, so how can that be the answer?

For the purposes of this blog, the swine flu is just a chunk of information that has the ability to be transferred from one node of a social network to another. It's a reminder that social transmission of information can have bad consequences as well as good ones, and that the ultimate health of the social network is determined by how well it can discriminate between the two. Twitter seems to be a very useful medium for transmission of memes. The network of twitters seems to act as an intelligent filter which exponentially removes things I'm not interested in while delivering to me stuff that I am interested in. Facebook has recently seemed very effective at transmitting "quizzes" to me, which I'm not thrilled with, but seems to be evolving in a more self-aware way.

And in case you wondered, there is
  1. no chance you'll get swine flu just by reading this
  2. ...because I am perfectly healthy and showing no symptoms
  3. ...but you may want to contact your local health authorities just to be sure
  4. ...and since you've read it anyway, go wash your hands.


  1. Couldn't agree more! ( Just off to wash my hands in case you infected my keyboard, lolol)

  2. If I sneezed in the middle of reading this post - then twittered the link to the blog - and I had bacon for breakfast, do my chances of getting h1n1 rise?

    Just curious.

  3. S Pilsk: Scientists have not confirmed the links between twittering bacon and contracting h1n1.