Lang introduces the principle, experimentally documented, that "learning material easily, or fluently, may sometimes produce shallower levels of learning" and that "when students encounter cognitive disfluency, and have to put in more work in processing the material, it may sink in more deeply."
He then offers a number of suggested applications, including this:
Plan for failure. A faculty member in chemistry said you can wake students up by asking them to undertake short experiments that are designed to fail. Rather than simply going through the motions of a lab, and finding the expected result planned for them by the teacher, students learn what every experienced researcher in the world knows: that experiments, like scholarly research of any kind, almost never proceed exactly as you planned them, and that you can learn a lot from your failures.
James M. Lang, "The Benefits of Making It Harder to Learn," Chronicle of Higher Education, published online at https://chronicle.com/article/The-Benefits-of-Making-It/132056/ on 3 June, 2012. Accessed 201200610.