If you’ve ever blocked out an entire afternoon to drill one topic — fifty algebra problems in a row, or a whole chapter of Spanish verbs — you’ve practiced blocked practice. It feels productive. The problems get easier as you go. But research consistently shows that this comfort is an illusion, and a rival technique called interleaving produces dramatically better long-term learning, even though it feels harder while you’re doing it.
Interleaving means mixing different but related categories of problems or topics within a single study session — instead of AAAA BBBB CCCC, you practice ABCABCABC. It sounds like it should be worse. It isn’t.