It is a great pleasure to me to write this Foreword to the book by Zhisheng (Edward) Wen. Edward completed his doctoral studies some years ago under my supervision at the Chinese University of Hong Kong (CUHK). I was blessed with a wonderful cohort of research students at CUHK before my retirement, and now I have the ultimate reward of one of them publishing a major monograph in the field of applied linguistics.

The book has brought together a number of literatures, and thus can make important contributions to applied linguistics. Most obviously, the book fills an important niche in applied linguistics by providing a thorough analysis of the construct and the measurement of working memory. There have been many journal articles in this area in recent years, and much progress in the neighbouring field of cognitive psychology. But we have needed a clear, up-to-date and comprehensive account of the area, as it applies to second language acquisition. This book fulfils that need. It reviews the general evidence and underpinning theory. This represents a real service for our field, where we tend to be more focused on applications than on basic issues. The updating here is timely, indeed.

The book also examines the considerable literature that has been written specifically from the perspective of second language acquisition. In doing this, it uses wider reviews, for example of working memory theories and measures, to demonstrate some of the shortcomings of existing research. But then the book provides an extensive and extremely useful review of measurement and related issues. Edward argues that second language research using working memory measures has to become much more sophisticated than it has been in the past. Indeed, one of the problems with some current second language research is its dependence on partial measures of working memory.