Michael H. Long (Ph.D. UCLA, 1980) is Professor of SLA at the University of Maryland. Recent publications include Sensitive periods, language aptitude, and ultimate L2 attainment , co-edited with Gisela Granena (John Benjamins, 2013), and Second language acquisition and Task-Based Language Teaching (Wiley-Blackwell, 2015). Gisela Granena (Ph.D. Maryland, 2012) is an Assistant Professor at the Universitat Oberta de Catalunya, Barcelona, where she coordinates English language courses and teaches language teaching methodology at the graduate level. Her research interests include implicit and explicit L2 learning, age effects, and cognitive individual differences. Yucel Yilmaz (Ph.D. Florida State, 2008) is Assistant Professor of Second Language Studies at Indiana University, where he teaches courses on second language acquisition and instruction. His research interests include negative feedback, task-based language teaching, computer-mediated communication, and individual differences.

Fifty years of modern research have yielded findings on some major research issues in SLA, including relationships between the L1 and L2, the learner and learning processes in interlanguage development, and the role of the linguistic and broader social environment.

Table of Contents:

Editorial - by William C. Ritchie and Tej K. Bhatia, Editors-in-Chief

Introduction
Major Research Issues in SLA - by Michael H. Long

Part 1:
Age Differences, Maturational Constraints, and Implicit and Explicit L2 Learning - by Gisela Granena

Part 2:
The Linguistic Environment, Interaction and Negative Feedback - by Yucel Yilmaz

The past 50 years have witnessed achievement of a set of widely attested empirical findings on major research issues in SLA. They pertain to such matters as cross-linguistic influence; processes and sequences in interlanguage development; age effects; incidental and intentional, learning and implicit and explicit knowledge; the role of the linguistic environment and of the broader social context as sources of positive and negative evidence and of opportunities for input, interaction and output; and effects of individual differences in language aptitudes and other cognitive and affect variables. Robust findings in any scientific field constitute empirical 'problems' that require explanation and motivate theoretical work. In this inaugural volume of Brill Research Perspectives in Multilingualism and Second Language Acquisition , Michael Long, Gisela Granena and Yucel Yilmaz review work on a selection of these issues, and note implications of some of the work for language teaching, educational language planning, human migration, and other important matters of social concern.