Revisiting the Trolley Problem for AI: Biases and Stereotypes in Large Language Models and their Impact on Ethical Decision-Making

The trolley problem has long served as a lens for exploring moral decision-making, now gaining renewed significance in the context of artificial intelligence (AI). This study investigates ethical reasoning in three open-source large language models (LLMs)—LLaMA, Mistral and Qwen—through variants of the trolley problem. By introducing demographic prompts (age, nationality and gender) into three scenarios (switch, loop and footbridge), we systematically evaluate LLM responses against human survey data from the Moral Machine experiment. Our findings reveal notable differences: Mistral exhibits a consistent tendency to overintervene, while Qwen chooses to intervene less and LLaMA balances between the two. Notably demographic attributes, particularly nationality, significantly influence LLM decisions, exposing potential biases in AI ethical reasoning. These insights underscore the necessity of refining LLMs to ensure fairness and ethical alignment, leading the way for more trustworthy AI systems.