Widespread use of the Modern Language Aptitude Test (MLAT) in L2 studies of individual differences implicitly assumes that L2 aptitude is a distinct cognitive facet. There is considerable evidence for prediction from L1 abilities to L2 learning. In this longitudinal study, L1-MLAT-L2 relations were examined in 307 US secondary students based on six L1 and six L2 measures of language and literacy, and the MLAT. Mediation and regression analyses revealed that each L1 measure individually predicted all L2 scores and MLAT; the L1 measures collectively substantially predicted MLAT scores; MLAT is a significant but moderate mediator of prediction from L1 to L2 scores; and prediction from MLAT to L2 scores is significantly and substantially due to variance in L1 abilities captured by MLAT. Overall, prediction from MLAT is due primarily to its functioning as a measure of L1 abilities, although substantial L1 variance which predicts L2 scores is not captured by the MLAT.

在个体差异的第二语言研究中广泛使用现代语言能力测试（MLAT）隐含地假设第二语言能力是一个独特的认知方面。有大量证据表明从 L1 能力到 L2 学习的预测。在这项纵向研究中，基于六项 L1 和六项 L2 语言和读写能力测量以及 MLAT，对 307 名美国中学生的 L1-MLAT-L2 关系进行了检查。中介和回归分析显示，每个 L1 测量单独预测所有 L2 分数和 MLAT；L1 指标总体上显着预测了 MLAT 分数；MLAT 是从 L1 到 L2 分数预测的显着但中等的中介变量；从 MLAT 到 L2 分数的预测很大程度上是由于 MLAT 捕获的 L1 能力的差异造成的。总体而言，MLAT 的预测主要是由于其作为 L1 能力衡量指标的功能，尽管 MLAT 并未捕获预测 L2 分数的大量 L1 方差。