In this morning's journal club we discussed Fowler and Christakis's "Dynamic spread of happiness in a large social network: A longtiudinal analysis over 20 years in the Framingham Heart Study". The authors are American doctors working in the field of medicine, public health and political science. Their work makes use of the Framingham Heart Study to analyse family and friendship ties, diet, lifestyle and a sense of well-being and have demonstrated that these behaviours and moods can spread through social networks similar to viruses. Obesity tends to spread through same-sex friendships. Starting and stopping smoking is more contagious than obesity and spreads across both sexes while the transmission of happiness tends to involve face-to-face happiness. Their new book is called Connected.
Network effects are the same as the peer effects that have been discussed recently in the blog in the context of education. The key challenge is identification: just because something is correlated within a group or is spreading within a group does not imply contagion. There may simply be a common cause. The book Social Dynamics, edited by H. Peyton Young & S. Durlauf is a good introduction to the social science side.
ReplyDeleteSo imagine some nasty person dispersed some virus on a particular group: you would gradually see them keeling over with the illness but it would not follow that it is contagious - though it might well be.
I don't know how these authors deal with this issue. In some cases you may be able to actually map the vectors.