The systems largely overlap, which implies that memories—fallible, mutable, and spread across almost every region of the brain—are being accessed, consciously and unconsciously, while we do everything from engaging in creative pursuits to problem solving. He calls it “constructive episodic simulation” (with “episodic” memories being personal moments we recall, vs. “semantic” memories, which are more facts and meanings.) The upshot: our memories aren’t sepia-toned artifacts, but modular building blocks. And our brains are using them like a 5-year-old plays with Lego—no instructions, and plenty of experimentation.