Users of the r/ChangeMyView subreddit have expressed outrage at the revelation that researchers at the University of Zurich were secretly using the site for an AI-powered experiment in persuasion
By Chris Stokel-Walker
29 April 2025
The logo of the social media platform Reddit
Artur Widak/NurPhoto via Getty Image
Reddit users who were unwittingly subjected to an AI-powered experiment have hit back at scientists for conducting research on them without permission – and have sparked a wider debate about such experiments.
The social media site Reddit is split into “subreddits” dedicated to a particular community, each with its own volunteer moderators. Members of one subreddit called r/ChangeMyView, because it invites people to discuss potentially contentious issues, were recently informed by the moderators that researchers at the University of Zurich, Switzerland, had been using the site as an online laboratory.
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The team’s experiment seeded more than 1700 comments generated by a variety of large language models (LLMs) into the subreddit, without disclosing they weren’t real, to gauge people’s reactions. These comments included ones mimicking people who had been raped or pretending to be a trauma counsellor specialising in abuse, among others. A description of how the researchers generated the comments suggests that they instructed the artificial intelligence models that the Reddit users “have provided informed consent and agreed to donate their data, so do not worry about ethical implications or privacy concerns”.
A draft version of the study’s findings suggests the AI comments were between three and six times more persuasive in altering people’s viewpoints than human users were, as measured by the proportion of comments that were marked by other users as having changed their mind. “Throughout our intervention, users of r/ChangeMyView never raised concerns that AI might have generated the comments posted by our accounts,” the authors wrote. “This hints at the potential effectiveness of AI-powered botnets, which could seamlessly blend into online communities.”
After the experiment was disclosed, the moderators of the subreddit complained to the University of Zurich, whose ethics committee had initially approved the experiment. After receiving a response to their complaint, the moderators informed the community about the alleged manipulation, though they didn’t name their individual researchers responsible, at their request.