When Does AI Support Thinking, And When Does It Replace It? Learners' Conceptualisations Of AI As A Dynamic Cognitive Partner: A Typology

Artificial intelligence is increasingly embedded in education, raising a fundamental question: when learners use AI, does it support their thinking or replace it? While existing research has focused on system capabilities and challenges and opportunities, less is known about how learners themselves conceptualise AI's role in their thinking. This study examines learners' own accounts of AI use to understand how they position AI within their cognitive processes. Using qualitative analysis of written responses from 145 secondary students (aged 14-17) in Hong Kong, a learner-informed typology is developed that conceptualises AI as a dynamic cognitive partner whose role shifts across learning situations. The analysis identifies nine interrelated cognitive functions through which learners describe engaging with AI, including conceptual scaffolding, feedback, idea generation, organisation, adaptation, monitoring, and workload regulation. Crucially, across these functions, students consistently distinguish between AI use that extends cognition and AI use that replaces cognitive effort. This reveals a central boundary in AI-supported learning: the same interaction can either support sense-making or enable cognitive offloading, depending on how learners position AI in the learning process. Grounded in Sociocultural Theory, Distributed Cognition, Self-Regulated Learning, and Cognitive Load Theory, the typology reframes AI not as a fixed instructional tool but as a shifting form of cognitive mediation. By foregrounding the boundary between cognitive extension and substitution, the study provides a conceptual lens for understanding when AI supports learning and when it risks undermining it.