Research has taught us a lot about memory in the past few decades. One of the key findings is that humans don't use only one memory system, but several. The first to develop is procedural memory, which we rely on for basic motor skills like rolling over, using a spoon, riding a bike -- or knocking a bottle into the bathtub because it makes a funny splash.
As your baby's brain develops and he becomes more aware of the world around him, he'll begin to have a semantic memory, too, which researchers define as knowledge about the world that extends beyond our bodies. Semantic memory allows us to make simple associations. "These are the things we feel like we intuitively just know," explains Stephen Christman, PhD, a memory researcher at the University of Toledo, Ohio.