Why do babies love peekaboo so much? It may be because when you hide your face, they think it has ceased to exist. That's according to Swiss psychologist Jean Piaget's theories about "object permanence," or the ability to know an object still exists even when it's hidden. Watching his 13-month-old nephew at play was when Piaget first noticed something unusual about the brains of babies. When the boy's ball rolled under a table where it was still visible, he would retrieve it and keep playing. But when it rolled under the couch where it wasn't visible, the boy looked for the ball where he had seen it last. This led Piaget to investigate exactly when babies develop object permanence.
A Baby's Demonstration of Object Permanence
His reaction is fascinating—and pretty funny, too.
Piaget's Conservation Tasks
Piaget also laid out other developmental stages with their own characteristics. Here's a demonstration of a four-year-old's lack of "conservation," or the ability to know that a quantity will stay the same despite a change in size or shape.
The Amazing Brains Of Babies
We can learn a lot by studying how babies think.
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