The importance of active learning. I've been reading and watching in English several texts and subtitled videos - respectively - for a while, and it has been rewarding to check that I've been able to fully understand what they were mostly about. Actually my level of understanding is such that I can complete successfully any kind of MOOC (massive online open course) which I want to enroll, even if they discuss complex topics like neuroscience or the theory of algorithms' complexity. However, this improvement of my English only concerns to these passive activities: reading and listening. Whenever I wanted to join a discussion about an interesting thing in a forum I found that I were able to express myself only after a lot of effort and very clumsily. In the same way, whenever I tried to keep a normal conversation with a foreigner or even to say to other people the name of really anything if English I found that I were completely null. In this sense, it is interesting to figure out how easy it is to fool ourselves in the learning process thinking that we have a deeper knowledge of a subject than we really have when we don't test ourselves and don't keep involved in "active" tasks.