For both groups, Duolingo represented 10% of their final grade. Both groups took the free placement test offered by Duolingo when you sign up for a new course.
The students participation in the study, therefore their use of Duolingo, represented 10% of the final grade in the class. Baseline data was collected with respect to their starting level which allowed the researchers to gauge what levels of Spanish were represented in the same.
Krashen (2014) points out in his rebuke of the Vesselinov and Grego (2012) study, in which they equated 34 hours of Duolingo to a university language course, that language learning is different from language acquisition. Krashen states that the activities presented in Duolingo (or in similar tutoring programs such as Rosetta Stone) involve conscious learning. In his opinion, conscious learning does not lead to language competence. He presents a summary of the research done by Mason, 2004; 2011; and Mason, Vanata, Jander, Borsch, and Krashen, 2009, noting that in his view, acquisition-oriented methods, which use subconscious learning, are superior to skill-based methods such as those used by Duolingo
This part and relevant research is useful for the "learning/Pedagogical Theory" tab under the "what does it mean to learn a language?"
spaced repetition, in which its algorithms detect when a user needs to review words or chunks that may have faded from memory.
An important feature