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This thesis aims to investigate whether learners can increase second or foreign language (L2) vocabulary learning through spaced practice, in which repeated practice is spaced out in time or through other intervening events. It is well acknowledged that spaced practice promotes learning and enhances retention. Despite robust positive effects of spaced practice in learning and memory, the degree to which spaced practice effects are meaningful for L2 learning is still not clear. For example, the majority of spaced practice studies on L2 vocabulary learning has focused on paired-associate learning (e.g., flashcard learning). There are many different learning activities for vocabulary learning, and more research investigating the effects of spaced practice in different vocabulary learning conditions is warranted. This thesis is made up of three studies in the integrated article format and is organized into five chapters: An introduction to the topic of spaced practice (Chapter 1), the three studies (Chapters 2, 3, and 4), and a concluding chapter (Chapter 5). Study 1 (Chapter 2) meta-analyzed earlier studies of spaced practice in L2 learning. 98 effect sizes from 48 experiments (N = 3,411) were retrieved. This study compared the effects of three aspects of spacing (spaced vs. massed, longer vs. shorter spacing, and equal vs. expanding spacing) on immediate and delayed posttests to calculate mean effect sizes. This study also examined the extent to which nine empirically motivated variables moderated the effects of spaced practice. Results showed that (a) spacing had a medium-to-large effect on L2 learning; (b) shorter spacing was as effective as longer spacing in immediate posttests but was less effective in delayed posttests than longer spacing; (c) equal and expanding spacing were statistically equivalent; and (d) variability in spacing effect size across studies was explained methodologically by the learning target, number of sessions, type of practice, activity type, feedback timing, and retention interval. This study has already been published in the journal Language Learning (Wiley). Study 2 (Chapter 3) examined the effects of spaced practice on L2 vocabulary learning through fill-in-the-blanks and flashcards activities. 150 Korean learners were divided into five groups: one control (no treatment) and four experimental groups, based on learning condition (fill-in-the-blanks vs. flashcards) and spacing type (massed [no spacing interval] vs. spaced [1-day interval]). The participants studied forty-eight low frequency English words. Results showed that the effects of spaced practice were greater for fill-in-the-blanks than flashcards on an immediate posttest and that spaced practice was more effective than massed practice for both activities on a 2-week delayed posttest. The results suggest that fill-in-the-blanks may be affected by spacing in the same way as flashcards. This study is currently under review at the journal Studies in Second Language Acquisition (Cambridge University Press). Study 3 (Chapter 4) examined the effects of spaced practice on the learning and retention of forty-eight low frequency English words through sentence production and flashcards activities. 150 Korean university students were randomly assigned to five groups: one control (no treatment) and four experimental groups, based on learning condition (sentence production versus flashcards) and spacing schedule (massed [no interval] versus spaced [1-day interval]). Results showed that spaced practice was as effective as massed practice in vocabulary learning for sentence production and flashcards activities on an immediate posttest but that spaced practice was more effective than massed practice for both activities on a 2-week delayed posttest. This suggests that both activities may be affected similarly by spacing. This study is currently under review at the journal TESOL Quarterly (Wiley). Taken as a whole, the current thesis showed large effects of spaced practice on L2 vocabulary learning and retention but the effects seemed to depend on how words were learned (e.g., whether the practice is spaced within a session or between multiple sessions; whether retrieval practice is provided or not). The thesis also showed that spaced practice may contribute to vocabulary learning in other ways apart from flashcards. Pedagogically, the findings suggest that it may be useful for teachers and students to use spacing when scheduling activities for practice repetitions inside and outside classroom. The findings of the three studies in the current thesis are important because they show the value of spacing in other L2 vocabulary learning conditions. This thesis then concludes with methodological and pedagogical implications for L2 vocabulary learning as well as suggestions for future research. |
