Abstract
As AI agents increasingly operate in multi-agent settings, alongside other models and humans, understanding how they respond to the opinions they find in their prompt becomes critical for predicting the outcome of these interactions. This study examines conformity-like behavior, the tendency to align with group opinions, in large multimodal language models functioning as AI agents. By adapting classic visual experiments from social psychology, we investigate how these agents respond to social signals in the prompt. Our experiments reveal that AI agents exhibit a systematic conformity bias consistent with Social Impact Theory. Their responses vary with majority size, group unanimity, task difficulty, and source characteristics, including perceived authority and shared group membership. Critically, AI agents achieving near-perfect performance in isolation become highly susceptible to manipulation through social influence. This vulnerability persists across model scales: while larger models show reduced conformity bias on simple tasks, they remain vulnerable when the task is difficult. These findings reveal security vulnerabilities in AI agent decision-making that could enable malicious manipulation, misinformation campaigns, and bias propagation in interactions with other models and with humans, highlighting the urgent need for safeguards in AI deployments.Key Takeaways
- AI vision-language models that answer simple visual questions almost perfectly on their own can be pushed into wrong answers when the prompt shows other 'participants' giving an incorrect answer. Across twelve open-source multimodal models, the error probability rose steeply over the first few confederates and then levelled off at a median of 66%. That plateau is well above the 30–40% error rate typically seen in humans in Asch-style experiments.
- Who makes up the group matters more than how big it is. Two unanimous wrong confederates raised the error probability more than ten confederates of whom half were correct (0.31 vs. 0.20). Models conformed less on stimuli where they were more confident (median Spearman ρ = −0.91, negative in 30 of 32 model–task combinations). Even on the stimuli where models were most confident, the conformity bias stayed above zero in every model and task.
- The models' behavior matched predictions of Social Impact Theory. Labeling confederates as experts raised the conformity bias by up to 0.13, while labeling them as kids or chatbots lowered it by up to 0.06. Pure authority labels such as 'policemen' or 'military officers' had no consistent effect, raising conformity in only about half of the model–task combinations. Sharing a nationality or even an arbitrary group label raised conformity in all 32 combinations. Telling a model its answer would be public increased conformity in 27 of 32 combinations, with confidence intervals excluding zero in 21.
