The phantom steering effect in Q&A websites.

Nicholas Hoernle, Gregory Kehne, Ariel D. Procaccia, Kobi Gal

Research output: Contribution to journalArticlepeer-review


Virtual rewards, such as badges, are commonly used in online platforms as incentives for promoting contributions from a userbase. It is widely accepted that such rewards “steer” people’s behaviour towards increasing their rate of contributions before obtaining the reward. This paper provides a new probabilistic model of user behaviour in the presence of threshold rewards, such a badges. We find, surprisingly, that while steering does affect a minority of the population, the majority of users do not change their behaviour around the achievement of these virtual rewards. In particular, we find that only approximately 5–30% of Stack Overflow users who achieve the rewards appear to respond to the incentives. This result is based on the analysis of thousands of users’ activity patterns before and after they achieve the reward. Our conclusion is that the phenomenon of steering is less common than has previously been claimed. We identify a statistical phenomenon, termed “Phantom Steering”, that can account for the interaction data of the users who do not respond to the reward. The presence of phantom steering may have contributed to some previous conclusions about the ubiquity of steering. We conduct a qualitative survey of the users on Stack Overflow which supports our results, suggesting that the motivating factors behind user behaviour are complex, and that some of the online incentives used in Stack Overflow may not be solely responsible for changes in users’ contribution rates.
Original languageEnglish
Pages (from-to)475-506
Number of pages32
JournalKnowledge and Information Systems
Issue number2
StatePublished - 2022


  • Amortised inference
  • Goal-gradient hypothesis
  • Privileges
  • Steering
  • Virtual badges

ASJC Scopus subject areas

  • Software
  • Information Systems
  • Human-Computer Interaction
  • Hardware and Architecture
  • Artificial Intelligence


Dive into the research topics of 'The phantom steering effect in Q&A websites.'. Together they form a unique fingerprint.

Cite this