While the popular belief may be that babies’ brains are blank slates, new research suggests that infants are born with some innate knowledge of their physical worlds, and they use that knowledge to learn, according to a paper published in the journal Science.
The researchers say their work builds on previous studies that have shown that very young babies are born with knowledge such as depth perception and the ability to tell whether or not an object is solid. This new study builds on this “core knowledge” theory by showing that babies notice unexpected situations in their physical world, and use that knowledge to learn.
Scientists have discovered that babies will spend much more time looking at things that adults find surprising or unexpected — when a ball appears to pass through a wall rather than bumping into it, for example — than at things that are not. For the last 30 years or so, scientists have used measurements of babies’ gazes to study everything from their ability to understand object permanence to differentiate sets of numbers.
The authors of the new study wanted to understand what the purpose of that behavior might be. Johns Hopkins University psychology doctoral student Aimee Stahl and psychology professor Lisa Feigenson designed a series of experiments in which they showed surprising and unsurprising events to 11-month-old babies. The events would either challenge or confirm what they know about physical objects. In the “surprise” group, for example, babies were shown a rolling ball that appeared to pass through a wall; the “unsurprising” group saw the ball stop rolling when it hit a wall.
Not only did the babies spent significantly more time watching the “surprise” event, but the “surprised” babies then seemed better able to learn about the ball. The psychologists tested this by “teaching” both groups of babies new information about the object. They moved the ball up and down, causing a squeaking noise. Later, when both groups of babies heard the squeaking noise while they were shown the ball along with a new object, a toy car, only the babies who had seen the surprising event gazed at the ball, implying they knew where the sound came from.
Researchers wanted to know more about how the babies learned about objects that surprised them, so they ran another experiment. One group of babies saw the same scenario as before — either a ball passing through a wall or a ball stopped by a wall. A second group saw a different set of surprising and unsurprising events — either a ball that appeared to float in the air, or a ball that rested on a box that supported it. Both groups were then given the ball and a toy car to play with. While the babies who hadn’t been surprised played with both objects equally, the “surprised” babies played with the ball for far longer.
They also seemed to be trying, on their own, to figure out the “surprising" event they witnessed. Babies who saw the ball pass through the wall banged the ball repeatedly, as if to test whether it was solid. Babies who saw the ball suspended in mid-air dropped it, as if to figure out whether it would float.
“Together, our work suggests that when infants witness an object defy their expectations, they learn about that object better, explore it more, and spontaneously test relevant hypotheses about the object’s behavior,” Stahl, the lead author of the study, said in a call with reporters on Wednesday.
The findings, the researchers say, build on previous results that have showed that babies have “sophisticated knowledge,” and that they take surprising events as “special opportunities to learn.”
In a famous 1959 experiment, Cornell University psychologists Eleanor Gibson and Richard Walk showed that babies as young as 6 months old stop crawling when they reach what appears to be the edge of a cliff reflected in a mirror, showing that they had depth perception. Cognitive psychologists such as Harvard University’s Elizabeth Spelke assert that babies as young as two months old seem to know that one solid object can’t pass through another. They’ve even demonstrated that newborn baby chicks and chimpanzees have some of these abilities.
Unlike psychologists such as Jean Piaget, who say children learn entirely through experience, these scientists believe babies and animals use knowledge they’re born with to learn.
“Infants' early expectations about the world can scaffold or guide their future learning,” Stahl said. “Our results highlight how nature and nurture profitably interact with one another.”