At Duolingo, striving for excellence is one of our core operating principles. We strive for excellence in our mobile app by devoting ourselves to a high-quality experience for every learner. As part of our commitment to building for a globally diverse audience, we've dedicated our efforts across the plethora of languages, operating systems, and mobile devices that our learners use. We run hundreds of A/B tests simultaneously, and staying on top of all possible versions of the app a learner might see depending on their user interface (UI) language, course, and device can become overwhelming. Until last year, there was no easy way to visually compare the same learner experience across multiple languages and devices to ensure a smooth, enjoyable experience for everyone.

At Duolingo, our goal is to make language learning fun and effective. We think the best education should be full of play, so we're constantly developing new features that make learning new things — and practicing old things — feel like a game! At the same time, we're serious about taking a scientific, data-driven approach to all of our products, and about sharing what we learn with the world. In this post, we'll take a look at the science behind the Duolingo skill strength meter, which we published in an Association of Computational Linguistics article earlier this year....

我学会用荷兰语说的第一句话是 "我们用棍子打死他们"。这不是语言课第一周的标准内容，但这又不是普通的语言课。作为一名研究16、17世纪文献的历史学家，我上的是一门学习阅读当时荷兰语的专业课--因此，我们没有学习如何谈论兴趣爱好或询问去火车站的路线，而是直接跳进了所谓的荷兰黄金时代的文章。