Are they human? Detecting large language models by probing human memory constraints
arXiv cs.AI / 4/2/2026
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Key Points
- The paper argues that online behavioral research validity depends on participants being human, but LLM-based agents can now pass many traditional “are you a human?” challenges.
- It proposes an alternative detection strategy: look for tasks where LLMs perform “too well” due to violating an established human cognitive limitation.
- The authors focus on limited working memory capacity and test a serial recall task to model and compare human cognition versus LLM behavior.
- Results indicate that cognitive modeling on this standard serial recall task can distinguish online participants from LLMs even when the LLMs are instructed to mimic human working-memory constraints.
- Overall, the study suggests that leveraging well-established cognitive phenomena can be a viable way to detect LLMs in human-subject settings.
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