What is elaborative interrogation?

Asking "WHY is this true?" for each fact and actually answering it — a generative study technique.

Instead of reading a fact and moving on, you stop and pose the question "why would that be the case?", then work out an answer. If the textbook says arteries have thick walls, you ask why — and reason that they carry blood at high pressure straight from the heart, so they need to resist it. That act of generating a reason is what makes the fact stick, because you've connected it to things you already understand rather than storing it as an isolated line to memorize.