Cette thèse a été subventionnée par Le Fonds de recherche du Québec – Société et culture (FRQSC) / Dans cette thèse, l’auteur s’est penché sur la question de l’apprentissage/enseignement du vocabulaire en français langue seconde (L2). Depuis plusieurs années, la recherche en L2 fait face à une question essentielle : celle de l’efficacité de différentes approches d’enseignement lexical afin de favoriser l’apprentissage des mots. Certains chercheurs (par ex. Krashen, 1982, 1989) considèrent que l’apprentissage du vocabulaire en L2, tout comme celui des aspects morphosyntaxiques, se produit uniquement de façon incidente pendant l’exposition aux différents échantillons de la langue (c.-à-d., l’intrant) et à travers des activités centrées sur le sens communicatif telles que la lecture de textes. D’autres (par ex. Laufer, 2005, 2006) préconisent une approche plus explicite de l’enseignement du vocabulaire, centrée sur les aspects formels des éléments lexicaux (form-focused instruction). Cette question n’a pas fait l’objet d’une recherche exhaustive, surtout en ce qui concerne les modalités de l’enseignement centré sur la forme (FFI) et le moment approprié (le FFI intégré vs le FFI isolé) pour le fournir, d’où l’importance de cette recherche. Trois études expérimentales ont été effectuées afin d’examiner l’efficacité de différentes approches d’enseignement du vocabulaire en français. Quarante-deux apprenants de français L2 ont participé à deux études de cas multiples (n = 9 et n = 10) et à une étude quasi-expérimentale (n = 23). Les deux premières études ont servi de pilotes pour l’élaboration de la méthodologie de la troisième étude. L'intervention expérimentale (quatre périodes de 45 minutes chacune) ciblant 36 mots a été réalisée à travers trois conditions expérimentales (FFI intégré, FFI isolé et répétition) et une condition de contrôle (apprentissage incident via la lecture). Chacun des participants a bénéficié de toutes les conditions. En d’autres termes, parmi les mots ciblés, certains devaient être appris incidemment, certains à travers une exposition répétée et certains ont été enseignés par le FFI intégré et le FFI isolé. Des tâches lexicales ont été administrées avant et deux fois après l'intervention. Les résultats indiquent les avantages du FFI en comparaison avec l'apprentissage incident et la répétition sans aucune différence significative entre le FFI isolé et le FFI intégré. La conclusion de cette thèse met l’emphase sur l’importance du FFI afin d’améliorer l’apprentissage du vocabulaire, tout en précisant le caractère indispensable des activités de récupération pour diminuer la perte de l’apprentissage produit. / In this thesis, the author examined the question of vocabulary learning/teaching in French as a second language (L2). L2 research has been interested in the effects of different approaches of lexical instruction on vocabulary learning. Some researchers (e.g. Krashen, 1982, 1989) contend that L2 learning, vocabulary and morphosyntax, occurs incidentally through the exposure to comprehensible input and through meaning-based activities such as reading. Others (e.g. Laufer, 2005, 2006) advocate a more explicit approach to vocabulary teaching, focused on the form of lexical elements. The effects of lexical form-focused instruction (FFI) have not been thoroughly investigated, particularly its different modalities and timing (integrated FFI vs isolated FFI), hence the relevance of this research. Three experimental studies were conducted to examine the effectiveness of different vocabulary teaching approaches in French as an L2. Forty-two L2 French learners participated in two multiple case studies (n = 9 and n = 10) and a quasi-experimental study (n = 23). Among other things, the first two studies were designed to serve as pilots for the methodological design of the third study. The experimental intervention (four periods of 45 minutes each) targeting 36 words was carried out through three experimental conditions (integrated FFI, isolated FFI and repetition) and a control condition (incidental learning through reading). Each participant benefited from all the conditions. In other words, among the targeted words, some had to be learned incidentally, some through repeated exposure and some were taught by the integrated FFI and the isolated FFI. Lexical tasks were administered before intervention started and twice after it ended (immediate posttest and delayed posttest). Results indicate the advantages of FFI compared to incidental learning and repetition. However, there is no significant differences between the isolated FFI and the integrated FFI. The conclusion of this thesis emphasizes the importance of FFI in order to improve the vocabulary learning, while specifying the necessity of the retrieval activities to reduce learning loss.

In many international schools where English is the language of learning and teaching there are large percentages of students whose first language is not English. Many of these students may have low vocabulary levels which inhibits their chances of taking full advantage of their education. Low vocabulary levels can be a particular problem for students in mainstream classes where fluent English speaking teachers are using English to teach content areas of Mathematics, Science and History. Not only do students have to comprehend the low-frequency, academic and technical vocabulary pertaining to the subject, but they also need to know the higher frequency vocabulary that makes up general English usage. If students’ vocabulary levels fall too far below the vocabulary levels with which their teachers are speaking, then their chance of comprehending the topic is small, as is their chance of succeeding in their subjects. This study has two broad aims. Firstly, I have set out to assess the English vocabulary levels of students at an international school where English is the language of learning and teaching. The majority of students at this school do not have English as their first language. The second aim of this study is to explore the vocabulary profile of the teachers’ spoken discourse at the research school. By gaining a better understanding of the nature of teacher discourse – specifically the percentage of high, mid and low-frequency vocabulary, as well as academic vocabulary that they use – English as a Second Language (ESL) teachers will be in a stronger position to identify what the vocabulary learning task is and be able to assist students in reaching the vocabulary levels necessary to make sense of their lessons. This study revealed a large gap between the generally low vocabulary levels of ESL students and the vocabulary levels spoken by their teachers. As a result the need for explicit vocabulary instruction and learning is shown to be very important in English medium (international) schools, where there are large numbers of students whose first language is not English. / Linguistics and Modern Languages / M.A. (Applied Linguistics)