Amy Morrison recently made a discovery during her 6-month-old baby's bathtime. "I stood Avery up against the tub to dry her off, and she pushed a plastic bottle of soap into the water," reports Morrison, who lives in Easton, Pennsylvania. "The bottle made a big splash, and she just started cracking up." Morrison fished the bottle out of the water several times and placed it on the edge of the tub. Each time, Avery repeated the action and made herself laugh.
But the real surprise came a week later, when Avery's father returned from a business trip. Morrison wondered whether their daughter would repeat the same trick for him, so she deliberately set the bottle of soap on the tub's edge. "Avery started giggling as she pushed the bottle into the water," Morrison marvels. "That made me wonder whether she actually remembered doing it the last time, or whether she was discovering it again."
Memories become more complex as baby's brain develops
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.
For a baby, that might mean knowing things like what applesauce looks like or that the stove could be hot. As he grows, his semantic memory will expand to include things like a green light means go, or a knock on the door signals that there are visitors.
As recently as a decade ago, researchers assumed that an infant's brain was too undeveloped to remember much more than these simple motor responses and associations for the first year of life. However, current memory studies reveal that babies are able to remember relatively complex pieces of information at a young age. What's more, your baby's memories can last for a long time, especially if you help him to strengthen them.
For instance, Carolyn Rovee-Collier of Rutgers University in New Jersey has demonstrated that 3-month-olds who see a sequence of actions modeled on a hand puppet -- like having a mitten removed -- can imitate those actions at 6 months of age when they develop the motor skills to perform them.
The key is that they need to be given reminders in between, like seeing the puppet for 60 seconds every three weeks. But with the right cues, "babies can remember something they learn at 6 months for up to two years," she says. While these findings may not seem all that relevant to a baby's day-to-day life (taking a mitten off of a puppet isn't a skill she'll use very often!), they show that visual cues can boost a baby's memory -- and also help her to navigate her surroundings.
For instance, when her daughter Meg was 8 months old, Virginia Smith of Brookline, Massachusetts, noticed that "whenever I walked her stroller in one direction, Meg would kick her legs, wave her arms, and act really excited." However, if they walked in the opposite direction, she howled in protest. What was going on? Smith had no idea, until Meg's babysitter explained that she often took the baby to a park in that "exciting" direction. The various landmarks on the way reminded Meg of where they were going -- and she knew that one direction meant fun.