Conversational agents are increasingly used in education for learning support. An application is "learning by explaining", where learners explain their understanding to an agent. However, existing research focuses on single roles, leaving it unclear how different pedagogical roles influence learners' interaction patterns, learning outcomes and experiences. We conducted a between-subjects study (N=96) comparing agents with three pedagogical roles (Tutee, Peer, Challenger) and a control condition while learning an economics concept. We found that different pedagogical roles shaped learning dynamics, including interaction patterns and experiences. Specifically, the Tutee agent elicited the most cognitive investment but led to high pressure. The Peer agent fostered high absorption and interest through collaborative dialogue. The Challenger agent promoted cognitive and metacognitive acts, enhancing critical thinking with moderate pressure. The findings highlight how agent roles shape different learning dynamics, guiding the design of educational agents tailored to specific pedagogical goals and learning phases.

翻译：对话代理在教育领域日益广泛地应用于学习支持。其中一项应用是“通过解释学习”，即学习者向代理阐述自己的理解。然而，现有研究多集中于单一角色，尚不清楚不同教学角色如何影响学习者的互动模式、学习成果与体验。我们开展了一项被试间研究（N=96），在学习经济学概念时，比较了具备三种教学角色（受教者、同伴、挑战者）的代理及一个控制条件。研究发现，不同的教学角色塑造了包括互动模式与体验在内的学习动态。具体而言，受教者代理最能激发认知投入，但会带来较高压力；同伴代理通过协作对话促进高度专注与兴趣；挑战者代理则能推动认知与元认知行为，在适度压力下增强批判性思维。这些发现揭示了代理角色如何塑造不同的学习动态，为针对特定教学目标与学习阶段设计教育代理提供了指导。