Observers have raised alarms about increasing political polarization of our society, with opposing groups unable to engage in civil dialogue to find common ground or solutions. Aggregators such as Digg, Reddit, and Google News rely on ratings and links to select and present subsets of the large quantity of news and opinion items generated each day. If a majority of the raters or linkers share a political viewpoint, minority viewpoints may get little representation in the results, creating an echo chamber for the majority. Even if a site selects items based on votes or links from people with diverse views, algorithms based solely on popularity may lead to a tyranny of the majority that effectively suppresses minority viewpoints. This work is the first attempt to formalize several different instances of the general concept of diversity of viewpoints and to devise algorithms that optimize for these measures. The techniques are likely to be applicable to other domains where selecting a diverse set of items is valuable, such as search engine results and audience voting on questions to ask of a conference speaker or public official. The goals of this research are to: 1) form alternative measures of diversity for result sets; 2) develop algorithms for selecting result sets that jointly optimize for diversity and popularity; 3) assess the impacts of alternative selection and presentation methods on people's willingness to use an aggregation service, their exposure to diverse opinions, and the size of their argument repertoires.
The results of the project will provide a better understanding of alternative notions of what it means for a set of items to be diverse or balanced, and the range of reactions that different people have to varying levels and presentations of diversity. Insight into people's preferences for acceptable support and challenge may also allow for the creation of news and opinion aggregators that cause people to choose to expose themselves to greater diversity, thus reducing polarization and enhancing democracy. Results, including open source software, will be distributed via the project web site: (http://si.umich.edu/balance/).
