This second edition is an updated, revised and restructured version of the first edition originally published in 1989. All chapters have been altered. We have deleted two chapters: the one on second language acquisition has now been omitted because the explosion in the amount of research necessitates a book on its own; however, we have retained some important aspects, integrating these into other chapters; for example, the social psychological processes at work in second language acquisition are discussed in Section 8.5 and communication strategies in second language learning in Section 9.2.2.3. The other deleted chapter is that on interpretation. We believe that the field is more relevant to cognitive psychology but has little to do with bilingual processing.

Owing to the rapid changes in the theoretical approaches and the increase in experiments and studies in the field, a number of chapters have been split up. Former Chapter 1 has been split into two chapters: Chapters 1 and 2. In addition to the definitions of bilingualism, the new Chapter 1 presents theoretical guiding principles which we follow throughout the book. The new Chapter 2 deals with the dimensions and measurement of bilinguality and bilingualism. Chapters 3, 4 and 5 are concerned with bilingual development and its consequences and in Chapter 5 we propose a social cognitive interactional model of bilingual development. Chapters 6 and 7 review the state of the art in the neuropsychology of bilinguality and the bilingual's information processing. Social psychological and interpersonal aspects are treated in Chapters 8 and 9, while Chapter 10 looks at societal bilingualism. Finally, Chapter 11 is concerned with language planning in education and with bilingual education.