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James P. Lantolf is George and Jane Greer Professor of Language Acquisition and Applied Linguistics, Director of the Center for Language Acquisition, and Co-director of Center for Advanced Language Proficiency Education and Research at The Pennsylvania State University. His research interests include Sociocultural Theory, second language acquisition, metaphor and conceptual knowledge. His is co-author, with S.L.Thorne, of Sociocultural Theory and the Genesis of Second Language Development (2006) and edits the Equinox journal Language and Sociocultural Theory

Matthew E. Poehner is Assistant Professor in the Department of Curriculum and Instruction and Professor-in-Charge of World Language Education at The Pennsylvania State University. His research interests include Sociocultural Theory, Dynamic Assessment and Concept-Based Language Instruction. He has published articles in Journal of Applied Linguistics, The Modern Language Journal, Critical Inquiry in Language Studies , and Language Teaching Research. He is author of Dynamic Assessment: A Vygotskian Approach to Understanding and Promoting Second Language Development (2008).