Take Caution in Using LLMs as Human Surrogates: Scylla Ex Machina

Abstract: Recent studies suggest large language models (LLMs) can exhibit human-like reasoning, aligning with human behavior in economic experiments, surveys, and political discourse. This has led many to propose that LLMs can be used as surrogates for humans in social science research. However, LLMs differ fundamentally from humans, relying on probabilistic patterns, absent the embodied experiences or survival objectives that shape human cognition. We assess the reasoning depth of LLMs using the 11-20 money request game. Almost all advanced approaches fail to replicate human behavior distributions across many models, except in one case involving fine-tuning using a substantial amount of human behavior data. Causes of failure are diverse, relating to input language, roles, and safeguarding. These results caution against using LLMs to study human behaviors or as human surrogates.