The use of social networking systems has enabled communication to occur around the globe almost instantly, with news about various events being spread around the world as they happen. There has also been much interest in the benefits and disadvantages the use of such social networking systems may bring for education. This paper reports on the use of Twitter in a Japanese university course, and the effect it had on the participants' autonomy. The second language learning motivation and metacognitive skills of 34 Japanese university students studying in a foreign cultures class were measured using both open-ended and closed-ended items in a questionnaire. The results suggest that only students who have high linguistic self-confidence will display progress in taking charge of their learning habits and becoming autonomous in their study as a consequence of using a social networking system in class.