Don't Worry When Kids Can't Size Things Up

Attempts to use toys that are too small part of normal development, study says

THURSDAY, May 13, 2004 (HealthDayNews) -- You may fret when your child tries to slide down a miniature slide, climb inside a tiny toy car, or squeeze her feet into doll shoes.

Relax and enjoy the visual humor, suggest researchers who report in the May 14 issue of Science that such errors of perception are a normal part of development.

"We're quite confident that on some level the kids know that it's too small," said study co-author David H. Uttal, an associate professor of psychology and education at Northwestern University.

He and his fellow researchers, from the University of Virginia and University of Illinois, have dubbed such errors "scale errors," and they think they are the result of immaturity and a lack of communication between two brain systems.

The trio of researchers decided to conduct a formal study after each had observed his or her own child -- or those they had seen in research settings -- try to interact or play with an object that was clearly too small to be used in the way the children attempted to use it.

For the study, the researchers first observed 54 children, aged 18 months to 30 months, in a playroom. They were interacting with a large indoor slide they could walk up and slide down, a child-sized chair they could sit in, and a car they could get inside and propel with their feet.

Then the children were taken for a walk and brought back to the playroom. They found miniature replicas of the slide, chair and car. The researchers drew the children's attention to the objects if they weren't already playing with them.

The researchers witnessed 40 "scale errors" -- incidents in which the children tried to interact or play with the miniature objects -- by 25 of the 54 children. The errors were most common among children 2 years of age and declined in the older kids.

The mistakes are similar, Uttal said, to what researchers call "slips of action" in adults. For instance, an adult sitting by a warm fire that's starting to flicker out may get up from the sofa intending to stoke the fire but mistakenly flip the television remote.

"We don't know if slips of action in adults and scale errors in kids are the same thing," Uttal said.

What the researchers think is happening among the children is, first, a failure of "inhibitory control." In other words, the brain doesn't say, "Stop, you're too big for the miniature slide." This reflects immaturity of the prefrontal cortex area of the brain, Uttal said.

There may also be a lack of communication between two brain systems, Uttal said.

"The visual recognition of an object, and the motor control of your brain telling your body how to move, are [controlled by] different parts of the brain," he said. "The part of the brain that actually controls the act of putting your body in the chair is not the same part of the brain that identifies the chair as something to sit in. Occasionally, the two don't talk to each other."

And that's when the errors occur.

Another expert praises the new research, saying it should help reassure parents of young children. "I think it's an extremely interesting and important study," said Susan Carey, a professor of psychology at Harvard University.

"If parents notice their kids doing this, I can't imagine them being worried about it," she said. "I think parents would just think it's hilarious and that's exactly the right reaction."

The researchers' explanation about the inhibitory system, Carey said, is probably correct. But, she added, more evidence is needed to prove the speculation that the two brain systems aren't "talking" to each other.

Uttal's team plans to continue the research. They invite parents to send examples of their children's scale errors to Uttal at

More information

To learn more about children's scale errors, visit the University of Virginia. Click on "Current Projects" to view video clips. To learn more about parenting, visit the American Academy of Pediatrics.

SOURCES: David H. Uttal, Ph.D., associate professor, psychology and education, Northwestern University, Evanston, Ill.; Susan Carey, Ph.D., professor, psychology, Harvard University, Boston; May 14, 2004, Science
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