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MONDAY, Aug. 25, 2003 (HealthDayNews) -- The skills a baby needs to understand a simple game of peek-a-boo are learned, not innate, a new study suggests.
The finding, reported in this week's issue of the Proceedings of the National Academy of Sciences, is sure to ignite the age-old debate about which skills babies are born with and which they must acquire.
Scott Johnson, an associate professor of psychology at New York University who led the recent study, is adamant: When it comes to learning certain aspects of how objects behave, babies must acquire the skill, he says.
Specifically, his team studied how infants obtain what scientists call their knowledge of object behavior or object permanence -- the ability to understand that objects exist even when they are no longer in sight.
In everyday situations, a baby with object behavior skills can play peek-a-boo, or understand that when a ball rolls behind a sofa, it will come out the other side.
Some experts used to think that infants learned the object permanence concept by manual exploration. But then research discovered that infants knew the concept even before their manual skills had progressed to the ability to reach and grasp. So some scientists suggested that the skill must be innate.
But Johnson's research suggests that infants learn the concept between 3 and 6 months of age, and they do it by visual observation.
In a series of experiments, Johnson's team tracked the eye movements of 80 babies, all between 4 months and 6 months old, as they watched a computer animation of a ball passing horizontally back and forth across the screen. At times, a box temporarily obscured the ball before it reappeared.
The eye movements of the 6-month-olds often anticipated that the ball would emerge from the other side of the box; their eyes darted over to the other side. But the younger infants rarely looked to the opposite side before the ball had actually arrived at the other side.
"The 6-month-olds would anticipate [the ball reappearing] much more reliably than the 4-month-olds," says Johnson.
Then, his team showed some of the 4-month-olds the ball moving back and forth on the screen without the box. "We let them look at it for two minutes." Then, when they showed these infants the ball being temporarily obscured by the box, "these kids looked just like the 6-month-olds," Johnson says.
"We've taught the 4-month-olds that this is the same [object] as what you saw before. It doesn't actually go in and out of existence," he adds.
"My study proves that the role of learning, early cognitive learning, has been very much underestimated," Johnson says. "People think that young babies are too inexperienced to pick up on these things, therefore it must be innate. What we are showing is a fundamental part of human cognition [the object permanence concept] can be learned early in infancy."
Richard Aslin, an expert in the field, calls the new study interesting, but says it won't put an end to the debate about whether object permanence skill is learned or innate.
One part of Johnson's research that is particularly interesting is the ability to "prime" the 4-month-olds to understand the concept, says Aslin, a professor of brain and cognitive sciences at the University of Rochester.
The study suggests that a little more exposure can accelerate performance, he says, "but we don't know whether accelerated performance sticks. We don't know if it has a permanent effect."
For parents, the good news is this, says Johnson: There's no need to buy any special toys or equipment to foster a child's skill in object permanence.
"Just spend time with your kids," he suggests. "They will pick it up automatically."
More information
For a demonstration of object permanence, go to the Massachusetts Institute of Technology. For information on early brain development, try the American Academy of Pediatrics.
