The purpose of the present paper is twofold; first, we present an empirical study evaluating the effectiveness of a novel CALL tool for foreign language vocabulary instruction based on spaced repetition of target vocabulary items. The study demonstrates that by spending an average of three minutes each day on automatically generated vocabulary activities, EFL students increased their long-term vocabulary retention rate three fold. Second, we demonstrate that the double-blind experiment design, which has become standard research practice in such extremely high-stakes fields as pharmacology and healthcare, has the potential of being successfully implemented in CALL research.