For a summary of the work that I did in graduate school, you might check out my thesis:

  • M. Harper, The Impact of Social Design on User Contributions to Online Communities. Ph.D. Thesis, University of Minnesota, 2009. [PDF]

Question and Answer Systems

Question and Answer (Q&A) sites (e.g. Yahoo! Answers) are places where people can ask questions and others answer them. We’re studying determinants of answer quality, and the incentives structures that govern these sites.

  • A. Pal, M. Harper, J. Konstan. Exploring Question Selection Bias to Identify Experts and Potential Experts in CQA. Forthcoming, TOIS.
  • J. Logie, J. Weinberg, M. Harper, J. Konstan. Asked and Answered: On Qualities and Quantities of Answers in Online Q&A Sites. ICWSM 2011. [PDF]
  • M. Harper, J. Weinberg, J. Logie, J. Konstan, Question Types in Social Q&A Sites. First Monday 15 (7) 2010. [Link]
  • M. Harper, D. Moy, J. Konstan, Facts or Friends? Distinguishing Informational and Conversational Questions in Social Q&A Sites. CHI 2009. [DOI] [PDF]
  • M. Harper, D. Raban, S. Rafaeli, J. Konstan, Predictors of Answer Quality in Online Q&A Sites. CHI 2008. [DOI] [PDF]
  • D. Raban, M. Harper, Motivations for Answering Questions Online. Book chapter in New Media and Innovative Technologies (Caspi, D., Azran, T. eds.), 2007. [Link]


Design principles concerning the construction of online communities are not well understood. We’re investigating (a) methods for personalization in online discussion forums, and (b) ways of mapping social psychology theories to the design of online communities.

  • Y. Ren, M. Harper, S. Drenner, L. Terveen, S. Kiesler, J. Riedl, R., Kraut. Building Member Attachment in Online Communities: Applying Theories of Group Identity and Interpersonal Bonds. Forthcoming, MISQ.
  • M. Harper, S. Sen, D. Frankowski. Supporting Social Recommendations with Activity-Balanced Clustering. RecSys 2007 Short Paper. [DOI] [PDF]
  • M. Harper, D. Frankowski, S. Drenner, Y. Ren, S. Kiesler, L. Terveen, R. Kraut, J. Riedl, Talk Amongst Yourselves: Inviting Users To Participate In Online Conversations. IUI 2007. [DOI] [PDF]
  • S. Drenner, M. Harper, D. Frankowski, J. Riedl, L. Terveen, Insert Movie Reference Here: A System to Bridge Conversation and Item-Oriented Web Sites. CHI 2006 Short Paper. [DOI] [PDF]

Social Preferences

Economic modeling is a powerful tool for understanding social processes. We’re using this tool to better understand why users contribute ratings to recommender systems, and how we can encourage additional contributions.

  • Y. Chen, M. Harper, J. Konstan, X, Li, Social Comparisons and Contributions to Online Communities: A Field Experiment on MovieLens. American Economic Review 100 (4) 2010. [DOI] [PDF]
  • M. Harper, Encouraging Contributions to Online Communities with Personalization and Incentives. User Modeling 2007 Doctoral Consortium. [DOI] [PDF]
  • M. Harper, X. Li, Y. Chen, J. Konstan, Social Comparisons to Motivate Contributions to an Online Community. Persuasive Technology 2007. [DOI] [PDF]
  • M. Harper, X. Li, Y. Chen, J. Konstan, An Economic Model of User Rating in an Online Recommender System. User Modeling 2005. [DOI] [PDF]
  • M. Harper, J. Konstan, X. Li, Y. Chen, User Motivations and Incentive Structures in an Online Recommender System. ACM Group 2005 Workshop Position Paper. [PDF]


  • X. Dong, M. Harper, J. Konstan. Entity-Linking Interfaces in User-Contributed Content: Preference and Performance. CHI 2011. [DOI]
  • J. McCarthy, B. Congleton, M. Harper. The Context, Content & Community Collage: Sharing Personal Digital Media in the Physical Workplace. CSCW 2008. [DOI] [PDF]
  • S. Sen, M. Harper, A. LaPitz, J. Riedl. The Quest for Quality Tags. ACM Group 2007. [DOI] [PDF]
  • D. Frankowski, S. Lam, S. Sen, M. Harper, S. Yilek, M. Cassano, J. Riedl. Recommenders Everywhere: The WikiLens Community-Maintained Recommender System. WikiSym 2007. [DOI]
  • S. Sen, S. Lam, D. Cosley, A. Rashid, D. Frankowski, J. Osterhouse, M. Harper, J. Riedl, tagging, community, vocabulary, evolution. CSCW 2006. [DOI] [PDF]