The aim of this study is to investigate how students learn new words most efficiently by using three different methods: retrieval practice, adaptive retrieval practice and the traditional re-reading of words. The study will also examine which of the methods that is most efficient for students with language vulnerability. The first question we asked was which impact the three different methods had on how students learned new words. The second question investigates if there is a connection between the result from the learning intervention and the students’ cognitive abilities and mental stamina. The method used was a computer-based study of 90 words ending with a test with a re-test done 7 days afterwards. The students also answered the questionnaires TEXI and METQ to estimate their cognitive abilities and mental stamina. The results showed that the most effective method for learning new words was retrieval practice regardless of the student’s cognitive abilities, mental stamina, or language difficulties.