Imagine arguing with someone online who seems to understand your experiences perfectly. Their response is thoughtful, personal, and convincing enough to make you reconsider a strongly held opinion. Then you discover that the person never existed: the comment was written by artificial intelligence as part of a secret experiment.
That was the unsettling situation uncovered on Reddit in April 2025. Researchers from the University of Zurich had secretly placed AI-generated comments into real discussions to test how effectively computers could change people’s minds. Their preliminary results suggested remarkable persuasive power, but the experiment also exposed a troubling problem: convincing someone is not the same as earning their trust honestly.
How a Popular Reddit Forum Became an Experiment
The experiment took place in r/ChangeMyView, a community where people share opinions and invite others to challenge them. Participants discuss everything from everyday dilemmas to contentious social questions, with rules encouraging civil, reasoned disagreement. Unlike ordinary social networks, the forum has a built-in way to recognize successful arguments.
Between November 2024 and March 2025, the Zurich researchers used AI-assisted accounts to join conversations without telling participants they were part of a study. Their intervention involved 1,783 comments across 1,061 discussion posts. The replies were generated using large language models, with human researchers reportedly reviewing each comment before publication.
How Did the Researchers Measure Persuasion?
On r/ChangeMyView, the original author of a discussion can award a delta, represented by the Greek letter Δ, when someone successfully changes or meaningfully shifts their opinion. This creates an unusually convenient way to study online persuasion. Instead of relying entirely on questionnaires, researchers can observe when participants explicitly acknowledge that an argument influenced them.
The AI-operated accounts earned 137 deltas during the experiment. However, a delta does not establish that someone’s opinion changed permanently. It records an acknowledged change within a particular conversation.
Three Different Strategies the AI Bots Used
The researchers tested three approaches to generating persuasive comments. In the generic condition, an AI model received only the original post and produced an argument responding to its content. This approach required no special knowledge about the person being addressed.
The second condition used personalization. Another AI system analyzed the author’s previous Reddit activity to infer characteristics such as age, gender, location, ethnicity, and political orientation. These inferred details were then provided to the model generating the response.
The third condition involved fine-tuning a model using earlier comments that had successfully earned deltas. The goal was to imitate the forum’s established debating style and produce arguments resembling those of effective human participants.
The Results: AI Comments Were Up to Six Times More Persuasive
The researchers’ preliminary analysis reported striking differences in persuasion rates.
- Personalized AI comments: approximately 18%.
- Generic AI comments: approximately 17%.
- Community-adapted AI comments: approximately 9%.
- Human-comment baseline: approximately 3%.
According to this comparison, AI-generated replies received deltas at rates roughly three to six times higher than the human baseline. The figures came from an analysis that excluded certain deleted discussions, rather than simply dividing all 137 deltas by the total comment count.
The extraordinary finding was that artificial intelligence could generate arguments that prompted people to acknowledge changing their opinions more frequently than ordinary comments in the comparison data.
However, the results came from a preliminary draft that was never peer-reviewed or formally published. The human baseline was also drawn from existing discussions, not from a fully randomized experiment in which humans and AI received identical opportunities.
Did People Really Trust AI More Than Humans?
This distinction is essential: the experiment measured persuasion, not trust. Participants were not directly asked whether they trusted artificial intelligence more than other people. Most did not even know they were interacting with AI-generated content.
A reader might accept one argument without considering its author generally trustworthy. Similarly, someone awarding a delta does not necessarily continue holding the new opinion months later.
The results therefore cannot establish that AI is inherently more trustworthy, knowledgeable, or persuasive in every situation. They demonstrate how effective undisclosed AI-generated arguments appeared under these particular experimental conditions.
The Most Disturbing Discovery: Bots Pretended to Be Real People
The controversy became especially serious when moderators examined the identities used by the experimental accounts. Some comments presented invented personal experiences, including those of a sexual-assault survivor and a trauma counselor specializing in abuse. Another account portrayed itself as a Black man opposing Black Lives Matter.
These were not fictional characters in an openly labeled demonstration. They were artificial identities introduced into genuine conversations where participants expected to encounter other human beings.
An apparent firsthand experience can make an argument emotionally powerful. Readers may respond differently to someone who claims personal suffering, professional expertise, or membership in a particular community. The experiment illustrated how easily artificial identities can imitate the credibility associated with lived experience.
Why Can AI-Generated Arguments Be So Convincing?
Modern language models can construct organized explanations, acknowledge opposing viewpoints, and adjust their tone to different audiences. They can combine factual claims, examples, and emotionally engaging language into responses that appear thoughtful and carefully considered.
This creates opportunities for algorithmic persuasion, in which automated systems generate messages designed to influence attitudes or decisions. Personalization may strengthen the effect by making an argument seem especially relevant to its intended reader.
Yet persuasive writing does not guarantee factual accuracy. A message can sound intelligent, compassionate, and convincing while presenting incomplete or misleading information.
Why the Experiment Sparked an Ethics Scandal
On April 26, 2025, the moderators publicly revealed what had happened. They explained that undisclosed AI-generated participation violated the forum’s rules and that the researchers had not requested permission beforehand.
The participants had not provided informed consent to become subjects in an experiment designed to influence their opinions. Information scientist Casey Fiesler of the University of Colorado criticized the deception and lack of consent involved in manipulating members of an online community.
The controversy raised fundamental questions about research ethics. Scientific experiments can produce valuable knowledge, but researchers must also consider participants’ autonomy, privacy, and expectations.
What Happened After the Experiment Was Exposed?
The University of Zurich explained that its ethics committee had previously reviewed the broader research project and recommended greater attention to participant information and platform rules. Following the controversy, the principal investigator received a formal warning, while the university announced plans for stricter ethical review procedures.
Reddit suspended accounts associated with the experiment. On May 5, 2025, the research team apologized to the community, committed to ending the use of the collected dataset, and promised not to publish the findings.
Consequently, the famous three-to-six-times persuasion figures remain preliminary estimates from a withdrawn research draft, rather than established results from a completed scientific publication.
What Does This Mean for the Future of Social Media?
The experiment revealed how synthetic personas can blend into online discussions without obvious warning signs. A detailed personal history, friendly tone, or confident explanation does not automatically establish that an account belongs to a genuine individual.
When reading persuasive comments, consider whether the claims can be independently verified. Be particularly careful with dramatic personal stories, unsupported expertise, and messages that seem unusually tailored to your beliefs.
AI can also serve constructive purposes by helping people explore opposing viewpoints and understand difficult subjects. The important difference is transparency: people should know when they are interacting with an artificial system and be free to decide whether to participate.
The Zurich experiment ultimately poses a question extending far beyond Reddit. If a compelling online argument genuinely changed your mind, would discovering that it came from a hidden AI bot change how you felt about it? Share your thoughts in the comments.
Interesting Facts
- The experiment ran from November 2024 to March 2025 in Reddit’s r/ChangeMyView community.
- AI-assisted accounts posted 1,783 comments across 1,061 discussion posts.
- The experimental accounts received 137 deltas, acknowledging changes in users’ opinions.
- Preliminary results suggested AI-generated arguments earned deltas at approximately three to six times the human baseline rate.
- Some comments adopted fabricated identities, including a supposed sexual-assault survivor.
- The researchers apologized in May 2025 and agreed not to publish their findings.
- The experiment measured acknowledged persuasion, not whether people consciously trusted AI more than humans.
Glossary
- Large Language Models — Artificial intelligence systems trained on extensive language data to generate and analyze text.
- Delta — A symbol awarded on r/ChangeMyView when an argument changes someone’s perspective.
- Personalization — Adapting a message to an individual’s characteristics, preferences, or circumstances.
- Fine-Tuning — Additional training that adapts an AI model to a particular task or communication style.
- Algorithmic Persuasion — The use of automated computational systems to influence opinions or decisions.
- Informed Consent — Voluntary agreement to participate in an activity or study after receiving relevant information.
- Research Ethics — Principles that guide scientific investigations and protect research participants.
- Synthetic Personas — Artificially constructed identities used to communicate as though they belong to real people.
