Are These Documents Written from Different Perspectives? A Test of Different Perspectives Based on Statistical Distribution Divergence

Proceedings of the 21st International Conference on Computational Linguistics and 44th Annual Meeting of the ACL, pages 1057–1064, Sydney, July 2006. c⃝2006 Association for Computational Linguistics Are These Documents Written from Different Perspectives? A Test of Different Perspectives Based On Statistical Distribution Divergence Wei-Hao Lin Language Technologies Institute School of Computer Science Carnegie Mellon University Pittsburgh, PA 15213 U.S.A. whlin@cs.cmu.edu Alexander Hauptmann Language Technologies Institute School of Computer Science Carnegie Mellon University Pittsburgh, PA 15213 U.S.A. alex@cs.cmu.edu Abstract In this paper we investigate how to auto- matically determine if two document col- lections are written from different per- spectives. By perspectives we mean a point of view, for example, from the per- spective of Democrats or Republicans. We propose a test of different perspectives based on distribution divergence between the statistical models of two collections. Experimental results show that the test can successfully distinguish document collec- tions of different perspectives from other types of collections. 1 Introduction Conflicts arise when two groups of people take very different perspectives on political, socio- economical, or cultural issues. For example, here are the answers that two presidential candidates, John Kerry and George Bush, gave during the third presidential debate in 2004 in response to a ques- tion on abortion: (1) Kerry: What is an article of faith for me is not something that I can legislate on some- body who doesn’t share that article of faith. I believe that choice is a woman’s choice. It’s between a woman, God and her doctor. And that’s why I support that. (2) Bush: I believe the ideal world is one in which every child is protected in law and wel- comed to life. I understand there’s great dif- ferences on this issue of abortion, but I be- lieve reasonable people can come together and put good law in place that will help re- duce the number of abortions. After reading the above transcripts some readers may conclude that one takes a “pro-choice” per- spective while the other takes a “pro-life” perspec- tive, the two dominant perspectives in the abortion controversy. Perspectives, however, are not always mani- fested when two pieces of text together are put to- gether. For example, the following two sentences are from Reuters newswire: (3) Gold output in the northeast China province of Heilongjiang rose 22.7 pct in 1986 from 1985’s level, the New China News Agency said. (4) Exco Chairman Richard Lacy told Reuters the acquisition was being made from Bank of New York Co Inc, which currently holds a 50.1 pct, and from RMJ partners who hold the remainder. A reader would not from this pair of examples per- ceive as strongly contrasting perspectives as the Kerry-Bush answers. Instead, as the Reuters an- notators did, one would label Example 3 as “gold” and Example 4 as “acquisition”, that is, as two top- ics instead of two perspectives. Why does the contrast between Example 1 and Example 2 convey different perspectives, but the contrast between Example 3 and Example 4 result in …

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