The red-and-blue ball rolls down a ramp and, thanks to a little bit of trickery, seems to pass right through a purple wall.
The 11-month-old girl watching the demonstration appears surprised, then grasps the ball and bangs it on a table, testing whether it is actually solid. The unexpected event motivated the baby to learn.
Researchers on Thursday reported a series of experiments that demonstrated that babies actively sought to learn when they witnessed something surprising and were less inclined to learn when they saw something predictable.
Previous experiments had shown that infants stared for a longer time after seeing different kinds of surprising events but they did not look at the cognitive consequences of seeing such events, the researchers said.
"Our hypothesis was that infants might be using these surprising events as special opportunities to learn, and we show that is indeed the case," said cognitive psychologist Aimee Stahl of Baltimore's Johns Hopkins University, whose research appears in the journal Science.
The study involved 110 11-month-olds, with roughly equal numbers of girls and boys. They watched various demonstrations, some defying their expectations like a ball seeming to roll through a wall or hover in the air and others involving expected outcomes like a wall stopping the ball or the ball simply sitting on a platform.
"Infants are very adept learners, and can learn about the world through observation and exploration," Stahl said. "We found that babies learned new information about objects more efficiently if they saw that object do something unexpected than if it had done something expected."
The babies also preferred to explore objects that behaved surprisingly, doing so in a way that suggested they were seeking an explanation about the unexpected outcome.
"Infants who witnessed a ball pass through the wall, for example, tested that ball's solidity by banging it on a solid surface. But babies who witnessed a ball float in midair instead tested the ball's gravity by dropping it onto the floor," Stahl said.
In the experiments, the researchers basically resorted to magic tricks, Stahl said. For example, to make it appear as if the ball had rolled through a solid wall, Stahl reached through a hidden curtain and moved the ball to the other side of the wall while a screen obscured the baby's view.
Johns Hopkins cognitive psychologist Lisa Feigenson said the findings probably would apply to children of other ages as well.