The current trend of speakers of English as a second or an additional language (English language learners) outnumbering speakers of English as a first language (native English speakers) has shifted the focus of English language teaching from the nativeness principle to the intelligibility principle. Following the intelligibility principle, this review examined the effectiveness of interventions on the intelligibility of English language learners (ELLs) and the comprehensibility of their speech by native speakers in two related but independent meta-analytic studies. Study 1 focused on intervention studies for ELLs to improve intelligibility in their speech. Robust variance estimation (RVE) generated significant effect sizes of 0.62 (p = 0.00) from 33 effect sizes in 18 independent studies. Study 2 focused on interventions for L1 native English speakers to improve their comprehensibility of ELL speech. RVE generated a statistically significant effect size of 0.24 (p = 0.04) with 20 effect sizes in 10 independent studies. Moderating analyses revealed that the measures of intelligibility and comprehensibility, and the speech task type, were significant factors explaining the effect size variations between the included studies in both analytic reviews. However, the length of scales did not significantly differentiate the effectiveness of interventions. The effects of pronunciation instruction are not sensitive to research setting, and interventions aiming to change native English speakers’ (NESs’) attitudes towards ELLs’ accented English rather than those aiming to improve NESs’ familiarity with ELLs’ accented English have statistically significant effects. The current analysis generated unique and important implications for future educational practice and research on intelligible and comprehensible communication between L1 speakers and language learners beyond English.

当前，以英语为第二或第二语言的人（英语学习者）超过以英语为第一语言的人（以英语为母语的人）的趋势已经将英语教学的重点从母语性原则转移到可理解性原则上。遵循可理解性原则，本综述在两项相关但独立的元分析研究中检验了干预措施对英语学习者 (ELL) 的可理解性和母语者对其演讲的可理解性的有效性。研究 1 侧重于 ELL 的干预研究，以提高他们的演讲清晰度。稳健方差估计 (RVE) 产生的显着效应大小为 0.62 ( p= 0.00) 来自 18 项独立研究的 33 个效应量。研究 2 侧重于对以 L1 为母语的英语人士的干预措施，以提高他们对 ELL 语音的理解能力。RVE 产生的统计显着效应大小为 0.24 ( p= 0.04）在 10 项独立研究中具有 20 个效应量。调节分析表明，可理解性和可理解性的测量以及言语任务类型是解释两个分析评论中纳入研究之间效应大小差异的重要因素。然而，量表的长度并没有显着区分干预措施的有效性。发音教学的效果对研究环境不敏感，旨在改变以英语为母语的人 (NES') 对 ELL 口音英语的态度的干预措施，而不是旨在提高 NES 对 ELL 口音英语的熟悉程度的干预措施具有统计学显着效果。