Desirable difficulties are learning conditions that slow early progress but improve long-term retention and the ability to apply what was learned.
Where it comes from
UCLA psychologist Robert Bjork introduced the term in 1994.¹ Well-studied examples include spacing practice over time, mixing different kinds of problems (interleaving) and testing yourself in place of rereading. In an experiment by Henry Roediger and Jeffrey Karpicke, students who practiced recalling a text remembered more of it a week later than students who simply studied it again, even though the restudy group had felt more confident.²
Where it goes wrong
The phrase gets stretched to cover any hardship, as if tougher were automatically better. Bjork stresses that a difficulty is desirable when learners can meet it with effort. If they lack the background to respond, it simply gets in the way.
Talent Takeaway
End each training session with a few questions people answer from memory, and schedule a short follow-up a week later. It will feel less smooth than a polished recap. That is exactly why it works.
¹ Bjork, R. A. (1994). Memory and metamemory considerations in the training of human beings. In J. Metcalfe & A. P. Shimamura (Eds.), Metacognition: Knowing about knowing (pp. 185–205). MIT Press.
² Roediger, H. L., III, & Karpicke, J. D. (2006). Test-enhanced learning: Taking memory tests improves long-term retention. Psychological Science, 17(3), 249–255. https://doi.org/10.1111/j.1467-9280.2006.01693.x
Further reading: Brown, P. C., Roediger, H. L., III, & McDaniel, M. A. (2014). Make it stick: The science of successful learning. Belknap Press of Harvard University Press.