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User:Halfak (WMF)

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Aaron Halfaker
Aaron Halfaker, Science Man
Aaron Halfaker
Principal Research Scientist, Wikimedia Foundation
Think big. Measure what you can. Build better technologies.

About me

Hi. I'm Aaron Halfaker. I'm a scientist. See projects and publications below. I've been a Wikipedian since 2008. I mostly build tools and run studies, but I make edits where I can. In 2011, I started working with the Wikimedia Foundation as a research scientist. This is my staff account. See my volunteer account, User:EpochFail, for my non-staff work.

My work

My job is to build understanding about and support for the socio-technical fabric of the Wikimedia movement. I tend to focus on our computer mediated spaces (Wikipedia, Commons, Wikidata, Wikisource, etc.) and quality dynamics (patrolling, curation, newcomer training, etc.)

See The Rise and Decline for an example of my research and mw:ORES and mw:JADE for an examples of an experimental technologies I'm actively working on.

Disclaimer: I work for or provide services to the Wikimedia Foundation, and this is the account I try to use for edits or statements I make in that role. However, the Foundation does not vet all my activity, so edits, statements, or other contributions made by this account may not reflect the views of the Foundation.

Contact me



Aaron's last day as staff was July 20th, 2020. See User:EpochFail for his volunteer work.


Research barnstar
Pine 19:07, 15 January 2016 (UTC)

I've seen you quoted, in more than one news article about Wikipedia 15, discussing the decline in the number of Wikipedia contributors and what can be done about it. --Pine 19:07, 15 January 2016 (UTC)

Elitre (WMF) 14:25, 27 May 2016 (UTC)

Hey there. Sherry and I wanted to award you this barnstar for "being awesome". Sorry the rationale isn't much detailed: work logs are also not available :) Rock on, --Elitre (WMF) (talk) 14:25, 27 May 2016 (UTC)

The Original Barnstar
Thank you for your interesting lightning talk at the Wikimedia Conference 2017. Ijon (talk) 08:43, 4 April 2017 (UTC)


Peer reviewed

  • N. TeBlunthuis, B. M. Hill, and A. Halfaker. The effects of algorithmic flagging on fairness: quasi-experimental evidence from Wikipedia. arXiv preprint 2020. (under review) arxiv
  • Halfaker, A. & Geiger, S. ORES: Lowering Barriers with Participatory Machine Learning in Wikipedia (under review) [arxiv]
  • Smith, C. E., Yu, B., Srivastava, A., Halfaker, A., Terveen, L., & Zhu, H. (2020, April). Keeping Community in the Loop: Understanding Wikipedia Stakeholder Values for Machine Learning-Based Systems. In Proceedings of the 2020 CHI Conference on Human Factors in Computing Systems (pp. 1-14). [arxiv]
  • M. Kogan, A. Halfaker, S. Guha, C. Aragon, M. Muller, and R. S. Geiger. 2020. Mapping Out Human-Centered Data Science: Methods, Approaches, and Best Practices. In Companion of the 2020 ACM International Conference on Supporting Group Work (GROUP ’20). Association for Computing Machinery, New York, NY, USA, 151–156. https://doi.org/10.1145/3323994.3369898
  • C. Kinkeldey, C. Müller-Birn, T. Gülenman, J. J. Benjamin, and A. Halfaker. PreCall: A Visual Interface for Threshold Optimization in ML Model Selection. arXiv 2019 preprint. https://arxiv.org/abs/1907.05131
  • Asthana, S., & Halfaker, A. (2018). With Few Eyes, All Hoaxes are Deep. Proceedings of the ACM on Human-Computer Interaction, 2(CSCW), 21. pdf
  • Hall, A., Terveen, L., & Halfaker, A. (2018). Bot Detection in Wikidata Using Behavioral and Other Informal Cues. Proceedings of the ACM on Human-Computer Interaction, 2(CSCW), 64. pdf
  • Zhu, H., Yu, B., Halfaker, A., & Terveen, L. (2018). Value-Sensitive Algorithm Design: Method, Case Study, and Lessons. Proceedings of the ACM on Human-Computer Interaction, 2(CSCW), 194. pdf
  • Geiger, R. S. & Halfaker, A. 2017. Operationalizing Conflict and Cooperation between Automated Software Agents in Wikipedia: A Replication and Expansion of 'Even Good Bots Fight'. Proc. ACM Hum.-Comput. Interact. 1, CSCW, Article 49 (December 2017), 33 pages. DOI: https://doi.org/10.1145/3134684 pdf
  • Thebault-Spieker, J., Halfaker, A., Terveen, L. G., & Hecht, B. (2018, April). Distance and Attraction: Gravity Models for Geographic Content Production. In Proceedings of the 2018 CHI Conference on Human Factors in Computing Systems (p. 148). ACM. pdf
  • Morgan, J. T., & Halfaker, A. (2018, August). Evaluating the impact of the Wikipedia Teahouse on newcomer socialization and retention. In Proceedings of the 14th International Symposium on Open Collaboration (p. 20). ACM. pdf
  • Forte, A., Andalibi, N., Gorichanaz, T., Kim, M. C., Park, T., & Halfaker, A. (2018, January). Information Fortification: An Online Citation Behavior. GROUP'17 (pp. 83-92). ACM. (pdf)
  • Halfaker, A. (2017, August). Interpolating quality dynamics in Wikipedia and demonstrating the Keilana Effect. OpenSym'17 (p. 19). ACM. (pdf)
  • Goggins, S., Germonprez, M., Million, A. J., Halfaker, A., & Hemphill, L. Advancing the OCDX: Building Social Computing Infrastructure. CSCW'17 (pp. 421-424). ACM.
  • Geiger, R. S. & Halfaker, A. Open algorithmic systems: lessons on opening the black box from Wikipedia. AoIR'17 (pdf)
  • Sarabadani, A., Halfaker, A., & Taraborelli, D. Building automated vandalism detection tools for Wikidata. WWW'17 (pp. 1647-1654). (pdf)
  • Geiger, R. S., & Halfaker, A. Operationalizing Conflict and Cooperation between Automated Software Agents in Wikipedia: A Replication and Expansion of “Even Good Bots Fight”. CSCW'17 (pdf)
  • Yang, D., Halfaker, A., Kraut, R., & Hovy, E. Identifying Semantic Edit Intentions from Revisions in Wikipedia, EMNLP'17 (pp. 2000-2010). (pdf)
  • Johnson, I. L., Lin, Y., Li, T. J. J., Hall, A., Halfaker, A., Schöning, J., & Hecht, B. (2016). Not at home on the range: Peer production and the urban/rural divide. CHI'16 (pp. 13-25). ACM. (pdf)
  • Yang, D., Halfaker, A., Kraut, R. E., & Hovy, E. H. (2016). Who Did What: Editor Role Identification in Wikipedia. ICWSM'16 (pp. 446-455). (pdf)
  • Halfaker, A., Morgan, J., Pandian, Y., Thiry, E., Rand, W., Schuster, K., ... & Laniado, D. (2016). Breaking into new Data-Spaces: Infrastructure for Open Community Science. CSCW'16 (pp. 485-490). ACM. (pdf)
  • Halfaker, A., Keyes, O., Kluver, D., Thebault-Spieker, J., Nguyen, T., Shores, K., Uduwage, A., Warncke-Wang, M. (2015). User Session Identification Based on Strong Regularities in Inter-activity Time, WWW'15. ACM. (pdf)
  • Morgan, J. T., Halfaker, A., Taraborelli, D., Hwang, T., & Goggins, S. (2015). Advancing an Industry/Academic Partnership Model for Open Collaboration Research. CSCW'15. m:Research:Open Collaboration Systems Workshop
  • Schneider, J., Gelley, B., Halfaker, A. (2014). Accept, decline, postpone: How newcomer productivity is reduced in English Wikipedia by pre-publication review, OpenSym'14. ACM. (pdf)
  • Halfaker, A., Geiger, R.S., & Terveen, L. (2014). Snuggle: Designing for Efficient Socialization and Ideological Critique CHI'14. ACM. (pdf)
  • Geiger, R.S., & Halfaker, A. (2013). When the Levee Breaks: Without Bots, What Happens to Wikipedia’s Quality Control Processes? WikiSym'13. ACM. (pdf)
  • Halfaker, A., Keyes, O., & Taraborelli, D. (2013). Making peripheral participation legitimate: Reader engagement experiments in Wikipedia CSCW'13. (pdf)
  • Geiger, R. S. & Halfaker, A. (2013). Using Edit Session to Measure Participation in Wikipedia CSCW'13. ACM. (pdf)
  • Halfaker, A., Geiger, R. S., Morgan, J., & Riedl, J. (2013). The Rise and Decline of an Open Collaboration System: How Wikipedia's reaction to sudden popularity is causing its decline. American Behavioral Scientist. (pdf)
  • Geiger, R. S., Halfaker, A., Pinchuk, M., & Walling, S. (2012). Defense Mechanism or Socialization Tactic? Improving Wikipedia’s Notifications to Rejected Contributors. ICWSM’12. (pdf)
  • Halfaker, A., Kittur, A., & Riedl, J. (2011). Don't Bite the Newbies: How Reverts Affect the Quantity and Quality of Wikipedia Work, WikiSym’11. ACM. (pdf)
  • Halfaker, A., Song, B., Stuart, D. A., Kittur, A., & Riedl, J. (2011). NICE: Social translucence through UI intervention, WikiSym’11. ACM. (pdf)
  • Panciera, K., Halfaker, A., & Terveen, L. (2009). Wikipedians are born, not made: A study of power editors on Wikipedia, GROUP’09. ACM. (pdf)
  • Halfaker, A., Kittur, A., Kraut, R., & Riedl, J. (2009). A Jury of Your Peers: Quality, Experience and Ownership in Wikipedia, WikiSym’09. ACM. (pdf)


Committed identity
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