Fans of “Got Your Nose” take note: Unexpected experiences that violate infants' innate knowledge of the world, like a ball appearing to roll through a solid wall, stimulate interest and help them figure out where to focus their learning efforts. The discovery not only shows that very young babies already have sophisticated expectations, but that the ones who experience surprises learn more efficiently than those who don't.
“Our research shows these surprising events are special opportunities to learn,” said cognitive psychologist Aimee E. Stahl of Johns Hopkins University. “If there's a mismatch between what you predicted should happen and what you actually observed, that's a special opportunity to revise the knowledge that you have and learn something new.”
Many studies over the past few decades have documented that babies gaze longer at surprising things and display their piqued interest through measurable physical changes, like increased heartbeat. “But it has been mysterious what purpose these 'surprise' reactions served,” Stahl says. “Why do babies have these responses to surprising events, and what are the cognitive consequences?" The team suspected that learning might be part of the motivation.
To test the idea, Stahl and co-author Lisa Feigenson showed a group of 11-month-olds a series of expected and unexpected events. A ball or toy car, for example, rolled down an incline and was either stopped by a solid wall or appeared to pass through it. Similarly, a ball or car could roll into a gap in a track and fall to the ground, or it might appear to “magically” pass over it and keep going.
When given a choice, the infants touched, explored and played with the objects that defied their expectations much more often than they selected those that had behaved normally. And like budding scientists, the infants tested those objects for the specific behavior that had surprised them. When a toy car appeared to pass through a wall, the infants banged it to be sure it was solid. When it appeared to roll over an open gap, they picked it up and dropped it to be sure it would fall.
“It's really specific behavior, and it's remarkably sophisticated,” Stahl notes. “It's not that they just want to explore an object because it did something surprising. It's what we'd call hypothesis testing, like scientists do all the time, and babies seem to be doing the same thing. They are testing hypotheses to try and get an explanation for how that object behaved in a really strange way.”
The process appears to influence how quickly babies learn new information, the team adds. In one experiment, some of the babies were shown a ball seeming to pass through a wall, while others saw it stopped by the wall as expected. Then all the children were taught something new about the object that they couldn't have known before—it made a squeaking sound.
To test whether the infants actually learned this information, the researchers moved the squeaky ball and a control object up and down while a squeak sound played from a central location, and they recorded what the infants were looking at. Babies that had been surprised by the ball's earlier behavior paid more attention to it than their unfazed companions, showing that they did associate the sound with the ball. This evidenced real learning, not just increased attention, because when the team repeated the test with a rattling sound the babies had not heard before, the surprised infants didn't respond the same way.
“We found that the babies who saw the expected event failed to learn this new information, while those who saw the surprising event learned this new information really efficiently and really well,” Stahl explains. “This suggests that they were really trying to gain new information about this thing that had violated their expectations.”
The results, published this week in Science, appear to demonstrate that babies use surprising events to guide their cognitive growth in a world already awash with stimuli. “There's an overwhelming quantity of input in the environment,” Stahl says. “How does anybody, let alone a baby with comparably limited cognitive resources, figure out what they should pay attention to or learn about versus what they should ignore? I think our results show that the knowledge they are born with appears to guide what you should learn about or seek more information about in the future.”