In January 2011, a trio of researchers published the results of an experiment in which they demonstrated that students who read material in difficult, unfamiliar fonts learned it more deeply than students who read the same material in conventional, familiar fonts. Strange as that may seem, the finding stems from a well-established principle in learning theory called cognitive disfluency, which has fascinating implications for teachers. As the researchers pointed out in their article in the journal "Cognition," both students and teachers may sometimes judge the success of a learning experience by the ease with which the learner processes or "encodes" the new information. But learning material easily, or fluently, may sometimes produce shallower levels of learning. By contrast, "making material harder to learn," the authors wrote, "can improve long-term learning and retention. More cognitive engagement leads to deeper processing, which facilitates encoding and subsequently better retrieval." In other words, when students encounter cognitive disfluency, and have to put in more work in processing the material, it may sink in more deeply. If teachers want their students to form a "richer and more elaborate memory" for their course material, the implication seems to be that they should find ways to force students out of their normal learning and processing modes and into states of cognitive disfluency. But, of course, if they push them too hard toward disfluency, teachers may end up discouraging them and shutting off their learning altogether. The challenge that teachers face, then, is to create what psychologists call "desirable difficulties": enough cognitive disfluency to promote deeper learning, and not so much that teachers reduce the motivation of their students. This article offers four techniques that might push students out of their familiar ways of thinking: (1) Ask students to process or translate course material using unusual rhetorical or expressive modes; (2) Require students to argue on behalf of unfamiliar positions; (3) Ask students to find or identify mistakes; and (4) Plan for failure.