This study seeks to investigate the effectiveness of YouTube vocabulary tutorials on L2 vocabulary acquisition. More specifically, this study tests learners' ability to distinguish between the Spanish verbs "saber" and "conocer", both of which translate to "to know" in English. A pre and post-test were administered to students during two separate lessons that incorporated YouTube videos that were selected to present the target lexical pair. Two, university-level basic Spanish classes participated in this study. Each of the two classes received a different treatment during the lesson on the target forms: while Class A was shown a grammar tutorial that used explicit grammar teaching to explain the target forms, Class B viewed an authentic video in the target language that provided implicit instruction regarding the target forms. In addition to completing the pre-and post-tests, the students completed a survey to ascertain their perception of each of the videos, and which of the two best helped their acquisition of the target forms. This study aims to answer the following questions: a. Do authentic materials that include implicit instruction facilitate learner acquisition of vocabulary in an L2? b. What are learners' perceptions of authentic materials that use implicit instruction vs. materials that explicit instruction? Key words: Authentic materials, vocabulary acquisition, materials use, Spanish language teaching.
