Notre recherche relève de la didactique des langues et s´inscrit dans la réflexion sur le plurilinguisme et l’acquisition des langues. Cette étude examine le processus d’activation partielle d’une langue autre que la langue cible pendant l’apprentissage des langues. Notre étude a été conduite dans deux établissements scolaires au Liban auprès des apprenantes des classes d’EB7, possédant un répertoire langagier plurilingue et ayant appris la diglossie arabe comme l’arabe (dans une version dialectale à la maison et standard à l’école) comme L1 et la langue française comme L2 et l’anglais comme L3. Lors de leur apprentissage et production du français L2 et de l’anglais L3, ils mettent en œuvre leur compétence plurilingue à travers l’activation partielle de leur potentiel plurilingue. Nous allons montrer quelles sont les processus cognitifs qui entrent en jeu lors de l’apprentissage de la nouvelle langue l’anglais L3. Ainsi que les facteurs qui conditionnent l’activation des langues connues par les apprenantes et à quel niveau linguistique se réalise le plus fréquemment l’activation partielle de la langue autre langue que la langue cible. / Our research comes from the didactics of languages and is part of the reflection on plurilingualism and the acquisition of languages. This study examines the process of partial activation of a language other than the target language during language learning.Our study was carried out in two schools in Lebanon with students of EB7 classes, having a multilingual language repertoire and having learned the Arabic diglossic language as L1 and the French language as L2 and English as L3.During their apprenticeship and production of the French L2 and the English L3, they apply their plurilingual competence through the partial activation of their plurilingual potential.We will show what are the cognitive processes that come into play when learning the new L3 English language. As well as the factors that condition the activation of the languages known by the learners, and at which linguistic level, is most frequently realised, the partial activation of the language other than the target language.

The present diploma thesis focuses on the unconscious code-switching between second and third language. The main objective of this thesis is to deal with principles of unconscious code-switching, describe and categorize actual appearances of unconscious code-switching between second and third language. After introducing issues, the second chapter sums up the way of second and third language acquisition in terms of bilingualism and multilingualism. The third chapter presents a definition and theoretic bases of code-switching. The fourth chapter concerns the analysis of the reason for code- switching in terms of usage-based and psycholinguistic approaches. The fifth chapter presents a categorization of code-switching from syntactic and pragmatic perspectives. The sixth chapter concerns the analysis of cases of code-switching from recorded interviews and the explanation of possible factors causing unconscious code-switching. Key words: Unconscious code-switching, bilingualism, multilingualism, usage-based approach, psycholinguistic approach, function words, acquisition, second language, third language, WIPP