Robert Bjork’s central contribution to the cognitive science of learning is the concept of desirable difficulties — the deliberate introduction of obstacles that slow down practice but dramatically improve long-term retention and transfer.
His work with his wife and collaborator Elizabeth Bjork at UCLA has repeatedly shown that students and teachers alike are poor judges of what is actually being learned. A study session that feels productive (fluent rereading, familiar material) often produces worse outcomes than a session that feels frustrating (retrieval attempts, interleaved topics, spaced recall).
Fluera’s core design principle — that friction is a feature — traces directly back to Bjork. The Fog of War exam mode, the spaced repetition scheduler, the Socratic confidence slider, the refusal to let the AI summarise your notes: all of them are desirable difficulties by design.