Languages in contact, that is bilingualism at the societal level and bilinguality, its counterpart at the individual level, are an integral part of human behaviour. With globalisation and increasing population movements due to immigration and greater geographical and social mobility, and with the spread of education, contacts between cultures and individuals are constantly growing. While bilingual individuals already outnumber monolinguals, it can be expected that this trend will continue in the twenty-first century.

In this book we attempt to present the state of the art on the principal issues of bilingualism and languages in contact. Our approach is multidisciplinary insofar as we study the various phenomena at different levels of analysis: we analyse languages in contact first in the language behaviour of the individual, next in interpersonal relations, and finally at the societal level where we consider the role of language in intergroup relations. A better understanding of languages in contact calls not only for a multidisciplinary approach but for an interdisciplinary integration of these diverse disciplines (Blanc & Hamers, 1987). One of the major problems of an interdisciplinary approach is the integration of the macro- and the microlevels of analysis. Because of the great methodological and theoretical difficulties, very few scholars have attempted it, and even fewer succeeded. If at times our discussions lack an interdisciplinary scope, it is because the state of the art does not allow it yet.

Each level of analysis requires specific disciplinary approaches: psychological at the individual level, social psychological at the interpersonal level, and sociological at the intergroup level. These disciplines are brought together when the different levels of analysis meet.