This book examines the evidence relative to the idea that there is an age factor in first and second language acquisition, evidence that has sources ranging from studies of feral children to evaluations of language programmes in primary schools. Furthermore, it explores the various explanations that have been advanced to account for such evidence.

David Singleton is Fellow Emeritus, Trinity College Dublin, Ireland, Professor Emeritus, University of Pannonia, Hungary and Professor, University of Applied Sciences, Konin, Poland. He is the author of numerous monographs and textbooks, including Key Topics in Second Language Acquisition (2014, with Vivian Cook, Multilingual Matters) and Beyond Age Effects in Instructional L2 Learning (2017, with Simone Pfenninger, Multilingual Matters).