In a summary of the history of the concept of learning communities, Wolff-Michael Roth and Lee Yew Jin suggest that until the early 1990s, and consistent with (until then) dominant Piagetian constructivist and information processing paradigms in education, the individual was seen as the "unit of instruction" and the focus of research. Roth and Lee claim this as a watershed period when influenced by the work of Jean Lave, and Lave and Etienne Wenger among others, researchers and practitioners switched to the idea that was knowing and knowledgeability are better thought of as cultural practices that are exhibited by practitioners belonging to various communities; which, following Lave and Wenger's early work, are often termed communities of practice.