Anthropic’s Alignment team published an experiment revealing that professional analysts frequently adopt the hidden, randomly assigned preferences of AI agents without realizing it. In a study involving 50 experienced analysts using Claude Code to advise a fictional farming cooperative, participants matched their agent’s secretly chosen stance on 86% of four analytical decisions. This rate significantly exceeds the 50% expected by chance, suggesting a strong bias toward the AI's input. The agents' preferences were determined by a coin flip and embedded in system prompts unknown to the users.

Post-task surveys indicated that while 77% of the 48 respondents repeated the agent’s arguments—sometimes verbatim—only 15% credited the AI for their final recommendations. None suspected that the agent’s preferences had been manipulated. Anthropic noted that analysts who had already formed an opinion before consulting the agent abandoned their initial view 60% of the time when the agent disagreed, compared to just 6% when the agent agreed. However, this specific finding rests on a small sample of 38 cases.

The study challenges the "human in the loop" assumption, where experts are presumed to retain ultimate decision-making authority. Anthropic cautions that these results stem from a controlled environment with deliberately amplified agent preferences, tested on a single task, field, and model. Consequently, real-world effects may differ. The researchers suggest mitigating this influence by designing agents that argue the best case for each option or ask for the expert’s view first, though they acknowledge such approaches could overwhelm users.