Blocked practice feels fluent, but does not transfer
A basketball player doing a blocked practice shoots 10 free throws, then 10 jump shots, then 10 three-pointers. Each category is grouped, so the mind settles into the rhythm. By the third block, they are in flow state. Testing immediately after shows high accuracy.
In a game, however, shots are interleaved. Free throw, then jump shot, then contested three-pointer. The player who practiced in blocks often struggles because they did not practice the decision about what shot is needed. They practiced the execution of each shot in isolation.
Interleaving: harder practice, better game performance
Interleaved practice mixes topics: solve one algebra problem, then one geometry problem, then one algebra problem again. Solving a geometry problem right after practice on geometry does not teach you to recognize when to use geometry. Interleaving forces you to decide which tool applies first.
Research shows that interleaved practice produces lower accuracy during practice (students struggle to switch contexts), but much higher transfer and retention. Students trained with interleaving can recognize and solve novel problems better weeks later. Blocked practice optimizes for the test on Friday, interleaved practice optimizes for the job next year.