Simone E. Pfenninger is Assistant Professor of Psycholinguistics and Language Acquisition at the University of Salzburg, Austria. Her research interests include multilingualism, psycholinguistics and the age factor in SLA and she is co-editor (with Judit Navracsics) of Future Research Directions for Applied Linguistics (2017, Multilingual Matters).
David Singleton is Professor of Applied Linguistics at the University of Pannonia, Hungary and Fellow Emeritus, Trinity College, Dublin, Ireland. He has published widely on second language acquisition, multilingualism and lexicology and is co-author (with Vivian Cook) of Key Topics in Second Language Acquisition (2014, Multilingual Matters).