Most teachers and language learners agree that vocabulary is one of the most important areas of language learning because it carries the main information load in a communicative situation. Some linguists (e.g. Lewis, 1993) go as far as to claim that language acquisition is basically a matter of developing lexical competence in the target language. However, although the importance of vocabulary knowledge to the ability to use the language seems obvious, how that knowledge develops and how - and even whether-it should be taught explicitly remains the subject of great debate. Numerous studies on the nature of vocabulary learning, vocabulary size, word frequency and representation of words in the mental lexicon published in recent years have improved our understanding of vocabulary acquisition and pedagogy. The studies, however, have also often produced different, even conflicting results about the effect of vocabulary instruction on lexical proficiency of the students.
For the classroom teacher looking to the research literature for guidance, this presents a problem. Vocabulary is an integral part of the second language curriculum but how it is handled in the classroom depends on a number of factors. Whether it is taught explicitly or implicitly, the methods used to teach and test it, and amount taught depends on the proficiency level and learning goals of the learner, as well the domain (reading, writing, listening & speaking) taught are all of potential importance.
The central aim of this dissertation is to assess the efficacy of semantic link-based instruction in the development of vocabulary knowledge in a foreign language instructional context. Semantic links are relationships between words that make up the semantic network by which lexical knowledge is represented in the mind of the language users be they native speakers or language learners.
Two kinds of semantic link knowledge will be examined in the dissertation: context– independent word associations in which lexical items are related to other words in the language, and text-based lexical links where the semantic links are defined in relation to other words in the text. Both are based on associative learning.
Three studies were conducted with advanced adult Japanese learners of English enrolled in a private language school in Tokyo. All studies were conducted in an advanced reading class. In Study One vocabulary learning through word associations, explicit definitions and inferring word meaning from context was examined. Study Two investigated text-based lexical links as a possible criterion for the selection of the target vocabulary in an L2 reading class. Items selected based on the richness of lexical links in the text were compared to words chosen based on teachers' intuition and general frequency of occurrence in the language. The study also examined the relationship between each of these methods and the effects of vocabulary pre-teaching on text comprehension and potential vocabulary growth. Study Three looked at the text-based lexical links as an instructional method in a second-language reading class. Instruction through semantic mapping, a technique employing the text-based lexical links, was compared to a more traditional word listing approach. Evaluation of each method was made based on implicit vocabulary learning and the results of reading comprehension tests.
The results of the study suggest that semantic-link based instruction offers potential advantages to advanced learners who have limited contact with the target language. The benefits come both in terms of quality of word knowledge and the effect on student motivation. The findings of the study also highlight the importance of establishing a clear standard for identifying the target vocabulary in L2 reading instruction. The pattern of results suggests that text-based lexical links may be a better criterion for vocabulary selection than frequency counts. Pedagogical findings and future research directions are discussed.