Vocabulary knowledge is one of the indispensable components of language learning. Because of the paucity of exposure to the target language in foreign language learning settings, the relationship between the numbers of time a learner encounters a word and classroom vocabulary learning seems to demand researchers’ serious attention. Spaced repetition, which involves distributing the repetitions of a given item, plays an important role in learning and retention. The present study investigated the impact of expanding and equal types of spacing and the massed condition on L2 receptive and productive vocabulary retrieval. The participants consisted of 63 pre-intermediate foreign language learners equally divided into one control and two experimental groups. Before the treatment, a teacher-made Vocabulary Knowledge Scale (VKS) was used to select twenty unknown word pairs (each word and its synonym) from a list of 35 word pairs chosen from the supplementary material used in the class (Oxford Word Skills, Intermediate, 2008). The twenty target word pairs were divided into two 10-item sets (sets A and B). During the treatment, the first experimental group studied set A under an equally spaced condition (2-2-2) and set B under an expanding spaced condition (0-1-5). The second experimental group studied set A and set B under expanding (0-1-5) and equally (2-2-2) spaced schedules, respectively, thus counterbalancing the effects of the target items. Both expanding and equally spaced schedules had the same absolute spacing, i.e. the total number of encounters, which was six. The control group studied all the target items consecutively every session under the no-spacing or massed condition (0-0-0). At the end of the experiment, the same VKS was used as a posttest to check the effects of the treatments. The results indicated that, although introducing spacing had enhanced both receptive and productive vocabulary retrieval (regardless of how the repetitions were spaced), an equally spaced schedule had led to a significantly higher mean score on the receptive items of the posttest and, therefore, better vocabulary retrieval. However, no such difference was observed between the means of the three groups on the productive items of the posttest.
Keywords: Vocabulary, equal spacing, expanding spacing, massed condition, Vocabulary Knowledge Scale, retrieval