Open-Ended NPC Dialogue Favors Casual Players: A Pilot Comparison of Three LLM-Driven Dialogue Systems

Non-player character (NPC) dialogue plays a crucial role in shaping the player experience in narrativedriven video games, influencing agency, immersion and story engagement. Despite the recent advancements in large language models (LLMs) for dynamic dialogue generation, few empirical studies have compared their impact across different dialogue system designs. This pilot study explores how LLM-driven dialogue systems affect the player experience using a custom-developed role-playing game (RPG) featuring four different dialogue designs; static control (CV), rephrase (A), hybrid (B) and fully open-ended (C). Behavioral data and post-game questionnaires were collected from 64 participants. Results indicate that fully open-ended dialogues led to significantly longer dialogue interactions and higher overall engagement, particularly among casual players, with the survey feedback highlighting its immersive and natural tone. These findings suggest that fully open-ended LLM-based dialogue in video games can enhance narrative depth and player involvement.