Online and in-person collaborative writing have similar benefits but different costs

With the rapid rise of online education, collaborative learning is no longer confined to physical classrooms. Yet, it remains unclear whether online collaboration, especially with or without visual cues, can support the same cognitive and neural processes as in-person collaboration. This study used multimodal learning analytics to compare collaboration processes and inter-brain synchronization (IBS) under three conditions: in-person, online with camera on, and online with camera off. Seventy-seven learner dyads completed a 28-minute collaborative writing task while their brain activity was recorded simultaneously using functional near-infrared spectroscopy (fNIRS). Across all three conditions, collaborative learning significantly improved outcomes. In-person and online (camera on) learners showed comparable IBS in the middle temporal gyrus. However, camera-on learners displayed more frequent higher-order behaviors (e.g., monitoring, questioning, mutual understanding, argument building) and greater dorsolateral prefrontal cortex activation, reflecting increased executive control demands. In contrast, camera-off learners achieved learning gains but engaged in less information exchange, emphasized mutual understanding and collaborative planning, and exhibited markedly lower IBS. Together, these findings indicate that while both in-person and online collaboration can yield similar levels of achievement, their cognitive costs differ: in-person collaboration is more efficient, whereas online collaboration requires additional regulation and cognitive effort. The absence of visual cues further constrains information sharing and social interaction, undermining IBS. These insights help explain the mechanisms that shape collaborative learning across contexts and offer guidance for designing more effective online learning environments.