There is a great deal of variation in gains found between studies of second language (L2) incidental vocabulary learning, as well as many factors that affect learning. This meta-analysis investigated the effects of exposure to L2 meaning-focused input on incidental vocabulary learning with an aim to clarify the proportional gains that occur through meaning-focused learning. Twenty-four primary studies were retrieved providing 29 different effect sizes and a total sample size of 2,771 participants (1,517 in experimental groups vs. 1,254 in control groups). Results showed large overall effects for incidental vocabulary learning on first and follow-up posttests. Mean proportions of target words learned ranged from 9–18% on immediate posttests, and 6–17% on delayed posttests. Incidental L2 vocabulary learning gains were similar across reading (17%, 15%), listening (15%, 13%), and reading while listening (13%, 17%) conditions on immediate and delayed posttest. In contrast, the proportion of words learned in viewing conditions on immediate posttests was smaller (7%, 5%). Findings also revealed that the amount of incidental learning varies according to a range of moderator variables including learner characteristics (L2 proficiency, institutional levels), materials (text type and audience), learning activities (spacing, mode of input), and methodological features (approaches to controlling prior word knowledge).

在对第二语言 (L2) 附带词汇学习的研究以及影响学习的许多因素之间发现的收益存在很大差异。这项元分析调查了接触 L2 以意义为中心的输入对附带词汇学习的影响，目的是阐明通过以意义为中心的学习所产生的比例收益。检索到 24 项主要研究，提供 29 种不同的效应量和 2,771 名参与者的总样本量（实验组 1,517 人，对照组 1,254 人）。结果显示，附带词汇学习对第一次和后续的后测有很大的整体影响。学习目标词的平均比例在即时后测中为 9-18%，在延迟后测中为 6-17%。附带的 L2 词汇学习收益在阅读中是相似的（17%，15%）、听力（15%、13%）和边听边读（13%、17%）在即时和延迟后测条件下。相比之下，在即时后测的观看条件下学习的单词比例较小 (7%, 5%)。调查结果还表明，附带学习的数量根据一系列调节变量而变化，包括学习者特征（L2 熟练程度、制度水平）、材料（文本类型和受众）、学习活动（间距、输入模式）和方法论特征（控制先验词知识的方法）。