Evaluating LLM-Generated Versus Human-Authored Responses in Role-Play Dialogues
It addresses the challenge of evaluating LLMs in long-form, knowledge-grounded role-play dialogues for professional training, providing a benchmark and hybrid evaluation framework, though it is incremental in assessing degradation.
This study compared LLM-generated and human-authored responses in multi-turn professional training simulations, finding that LLM response quality significantly degraded over turns in naturalness and context maintenance, while human responses improved, with participants consistently preferring human-authored dialogue.
Evaluating large language models (LLMs) in long-form, knowledge-grounded role-play dialogues remains challenging. This study compares LLM-generated and human-authored responses in multi-turn professional training simulations through human evaluation ($N=38$) and automated LLM-as-a-judge assessment. Human evaluation revealed significant degradation in LLM-generated response quality across turns, particularly in naturalness, context maintenance and overall quality, while human-authored responses progressively improved. In line with this finding, participants also indicated a consistent preference for human-authored dialogue. These human judgements were validated by our automated LLM-as-a-judge evaluation, where Gemini 2.0 Flash achieved strong alignment with human evaluators on both zero-shot pairwise preference and stochastic 6-shot construct ratings, confirming the widening quality gap between LLM and human responses over time. Our work contributes a multi-turn benchmark exposing LLM degradation in knowledge-grounded role-play dialogues and provides a validated hybrid evaluation framework to guide the reliable integration of LLMs in training simulations.