The effects of vocabulary instruction on English language learners

The effectiveness of vocabulary instruction for first language learners has been reviewed in several studies (Petty, Herold, & Stoll, 1968; Stahl & Fairbanks, 1986; National Reading Panel, 2000). However, the reviews of vocabulary instruction research focusing on learners of English as a second (ESL) or foreign language (EFL) are fewer in number. Because empirical research has explored more fully which vocabulary instruction is more useful for learning English vocabulary, there is a need for a study reviewing the results of research related to ESL or EFL students. Many empirical studies measured the effectiveness of some instruction individually in particular cases. Therefore, each instructional approach needs to be examined, reviewed, and integrated to determine the effectiveness as a whole. The findings will have implications for teaching vocabulary to ESL or EFL students. With the above purpose in mind, the following research questions guided my study. Each will be answered by integrating previous studies in this meta-analysis.
1. How can vocabulary instruction for English language learners used in quasi-experimental or experimental studies be categorized? 2. To what degree are these instructional methods effective? What are the effects of such methods on learning vocabulary for English language learners¡¯ achievement? 3. Under what conditions are these kinds of instruction effective? That is, what are the mediating effects of substantive variables affecting vocabulary instruction, such as the age of samples, their levels of English, geographical location, and the publication source of study? To review these various instructional methods with lesser bias and greater validity than the traditional review, a meta-analysis was conducted. Using meta-analysis techniques, the research relating to vocabulary instruction for English language learners was synthesized. Meta-analysis uses effect size as a common metric for comparing outcomes of each experimental or quasi-experimental study. The meta-analytic process has five basic phases (Glass, 1976): (1) formulating the problem, (2) collecting the data, (3) evaluating the data, (4) synthesizing the data and (5) presenting the findings. The categorization of vocabulary instructional studies indicated the variety of instructional approaches studied in the past three decades. Studies were categorized as contextualized instruction, semi-contextualized instruction, or decontextualized instruction. The three categories of studies were divided by multimedia and non- multimedia. The category of studies used multimedia as a teaching tool measured computer-related learning word programs. These computer programs were subcategorized as to whether they used first language supports in the programs. The overall effect size was d=.69 for this meta-analysis. Since the effect size is the same as a z score, an effect size .7 is the same as .2580 (about 26%). This means that if the control groups were to receive the treatment, their scores should improve about 26% on the average. Even though all of the instruction is effective for English language learners, decontextualizing instruction is the most effective for them. Decontextualizing instruction is focusing on the word meaning separately from context with a flash card or word list, or any other activities that focus on forms or core meanings of words. Contextual instruction shows the lowest effect size than the other two types of instruction.
The study indicates there are no different effects of vocabulary instruction on learning condition between ESL and EFL. The use of multimedia in vocabulary instruction was found to be more effective than control groups, but the effect size of multimedia groups was lower than the group without multimedia use. Therefore, it could be said that the use of a computer is not better than a classroom teacher. Although there are debates on the effectiveness of first language use for second language learners, the results of this study yielded no differences with or without first language supports, unless the instruction was associated with the other specific factors. This meta-analysis confirms that vocabulary instruction for ESL or EFL learners has some similarities and dissimilarities to that of first language learners. To determine more effective instruction for EFL or ESL learners, a consideration of the characteristics of learners and environments as well as instructional approaches should be made. From this study, it was concluded that effective instruction for English language learners depends on the conditions of vocabulary instruction. ESL and EFL classroom teachers need to consider the difference depends on the conditions of vocabulary instruction. ESL and EFL classroom teachers need to consider the differences of first and second language vocabulary acquisition as well as student learner characteristics.