Babies can remember far more than we realize, says Carolyn Rovee-Collier, Ph.D., a professor of psychology at Rutgers University, in Piscataway, NJ. She has tested memory in babies as young as 10 days old and says that infant memory works the same as adults' does: As we experience things, we create associations with them, and these associations become our memories.
If a baby sees or hears something only once, he won't retain it. But if he's reminded a few times over a short period of time, a song (or a face, or a toy) will stick with him. For instance, if you show a 3-month-old a stuffed dog for 60 seconds but you never remind him of it, he won't remember he saw it. But if you reintroduce it a few hours later and again the next day, Rovee-Collier's research tells us that your baby will still remember the dog up to two weeks later. Show it to him again a week later and he can remember it for twice as long. If he continues to see it (getting the chance to retrieve his memory of it) and the periods between seeing it get longer and longer, he may, theoretically, be able to remember the dog forever.
A great use for this surprising skill: Show your baby pictures of Grandma, who lives three states away. If you show him again the next day, then a few days later, and then periodically, by the time he and Grandma get to be together, she'll be a familiar face.