Implicit and explicit knowledge in second language learning, testing and teaching (review)

Questions about the relative contributions of implicit/explicit learning, knowledge, and instruction in second language (L2) acquisition have garnered considerable research attention in recent years. This collection by Rod Ellis and his colleagues is a valuable addition to this line of enquiry, providing a detailed and thought-provoking overview of the theoretical concepts, measurement techniques, and applications associated with work in this area.

In Part 1, Ellis lays the theoretical foundation for the book. Detailed definitions of implicit/explicit learning, knowledge, and instruction are presented along with information on the relationship between explicit and implicit knowledge. Part 2 focuses on a range of methods for measuring L2 implicit and explicit knowledge. As an introduction, Ellis reports in chapter 2 on a study of the reliability and validity of five tests of implicit/explicit knowledge (elicited oral imitation, oral narrative, timed grammaticality judgement, untimed grammaticality judgement, and metalinguistic knowledge). Four of these tests are addressed in detail in subsequent chapters. In chapter 3, Erlam focuses on the development and validation of one of the measures of implicit knowledge, the elicited oral imitation test, while in chapter 4, Loewen addresses the use of timed and untimed grammaticality judgement tests. In chapter 5, Elder investigates the validity of the metalinguistic knowledge test as a measure of explicit knowledge.

Part 3 illustrates how the measures can be used to investigate a wide range of current topics in L2 acquisition: the difficulty of learning various English grammatical structures (Ellis, chapter 6); the relationship between standardized language test scores and measures of L2 implicit/explicit knowledge (Elder and Ellis, chapter 7); the relationship between previous learning experiences and measures of L2 implicit/explicit knowledge (Philp, chapter 8); and the metalinguistic knowledge of pre-service teachers (Erlam, Philp, and Elder, chapter 9).

Part 4 continues this focus on applied research by providing a series of studies on the relationship between form-focused instruction and implicit/explicit knowledge. In chapter 10, Erlam, Loewen, and Philp investigate the impact of input- and output-based instruction, using the elicited oral imitation test and an untimed grammaticality judgement test. Loewen, Erlam, and Ellis use the same measures in chapter 11 to examine the incidental acquisition of the English third-person singular, while in chapter 12 Reinders and Ellis use timed and untimed grammaticality judgement tests to look at the effects of different kinds of input on the intake and acquisition of English negative adverbs. Part 4 concludes with Ellis, Loewen, and Erlam's chapter on the role of implicit and explicit corrective feedback in the acquisition of the English regular past tense as measured by an untimed grammaticality judgement test, elicited oral imitation test, and metalinguistic knowledge test. In Part 5, Ellis addresses some of the limitations of the research presented in the book and provides suggestions for future research.

While research on implicit and explicit L2 knowledge has been a productive line of research in recent years, it has also been noted that there is a 'lack of widely accepted means for measuring L2 explicit knowledge' (Ellis, 2004, p. 227). This collection of papers should prove invaluable in helping the field to standardize the operationalization and measurement of L2 implicit/explicit knowledge. As such, it should be required reading for both novice and experienced researchers. With its methodological rigour and clarity of explication, this book will serve as both a resource and a source of inspiration for many years to come.