A world in which everything is always the same. Image three different kinds of possible worlds: a world in which everything is always the same, everything is systematic. Prey animals are always predictable in number at the watering hole. Stranger always act the same way on meeting: a world in which everything is random, everything is always different. In a completely systematic world, learning would be unnecessary: what you need to know could be stored in dna. In a completely random world, learning would be pointless: no present experience would help you in future because everything would be different then. No one has ever seen a memory. But if we suppose that there is such a thing, then human and animal behavior becomes more predictable and explainable. Emphasizes processes by which information is transferred from stm to ltm. Control processes, include rehearsal, coding, and imagery.