We propose a framework for understanding epistemic curiosity as a metacognitive feeling state that is related to the individual's Region of Proximal Learning (RPL), an adaptive mental space where we feel we are on the verge of knowing or understanding. First, we review several historical views, contrasting the RPL perspective with alternative views of curiosity. Second, we detail the processes, conditions, and outcomes within the RPL framework which are proposed to be related to curiosity. Finally, we review several lines of evidence relevant to the relation between RPL and curiosity. These include (1) differences in the conditions under which experts and novices mind wander, (2) experiments investigating people's choices of whether to study materials for which they have high versus low feelings of knowing, (3) results related to people's engagement with corrections to errors made with high confidence, and (4) curiosity, attention, and learning data related to the tip-of-the-tongue state.
Keywords: curiosity; knowing; learning; metacognition; reward.