This article provides a comprehensive and critical synthesis of the methods utilized in studies investigating the role of language aptitude in second language acquisition (SLA). The synthesis is informed by sixty-five studies generated by a thorough search of the literature, three meta-analyses (Li, 2015, 2016, 2017), and a thematic issue of Studies in Second Language Acquisition (Li & DeKeyser, in press). The synthesis starts by identifying three categories of research investigating the role of aptitude in naturalistic learning, aptitude's associations with instructed learning, and the nature of aptitude pertaining to whether it increases with age and learning experience and how it is connected to other individual difference variables. The synthesis then presents an overview and critique of major measures of aptitude and discusses the construct validity of aptitude measures based on the principles of psychometric assessments. Specifically, the measures are scrutinized along the dimensions of reliability, content validity, divergent/convergent validity, and predictive validity. The content and measurement of implicit aptitude—a newly emerged construct in SLA—are highlighted. The synthesis proceeds to summarize and vet the measures of the outcome variable of aptitude research—L2 proficiency. Throughout the synthesis, methodological features are summarized, issues are identified, and remedies are proposed.

中文翻译：

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语言能力研究的方法：系统评价

本文对研究语言能力在第二语言习得 (SLA) 中的作用的研究中使用的方法进行了全面和批判性的综合。该综合是通过彻底搜索文献产生的 65 项研究、三项荟萃分析（Li，2015、2016、2017）和一个主题问题第二语言习得研究（Li & DeKeyser，出版中）。综合首先确定了三类研究，调查能力在自然主义学习中的作用，能力与指导学习的关联，以及能力的性质是否随年龄和学习经验而增加，以及它如何与其他个体差异变量相关联。然后，综合介绍了对主要能力测量的概述和批评，并讨论了基于心理测量学评估原则的能力测量的结构有效性。具体来说，这些措施是根据信度、内容效度、发散/收敛效度和预测效度的维度进行审查的。强调了内隐能力的内容和测量——SLA 中一个新出现的结构。综合继续总结和审查能力研究的结果变量-L2熟练度的度量。在整个综合过程中，总结了方法特征，确定了问题，并提出了补救措施。