Robert Bjork coined the term in 1994 to capture a counterintuitive empirical pattern: study conditions that feel easiest — fluent rereading, massed practice, familiar context — produce the worst long-term outcomes. Conditions that feel harder — spaced returns, retrieval under occlusion, mixed topics — produce the best.
The student’s intuition is almost always wrong. What feels productive is usually the illusion of competence (recognition mistaken for recall). What feels slow and frustrating is usually encoding in progress.
Fluera engineers desirable difficulties on purpose. Blank canvas where a template would be easier. Retrieval prompts before answers. Spaced returns that widen. Fog of War masking before exam day. Every friction in the product is a friction Bjork would recognise — and recommend.