Some people with developmental disorders make rhythmic movements that are common in very young children, such as continuously rocking back and forth. Since babies usually stop these behaviors by their first birthday, several researchers have predicted that it might be possible to identify children at risk of delayed development by observing their rhythmic movements.

Dr. Alan S. Unis and colleagues at the University of Washington in Seattle tested this idea in a study of 18 children who had an increased risk of delayed development because they had been born prematurely. The researchers compared the at-risk children with a "control" group of children who were not born prematurely.

The investigators evaluated the children's rhythmic behaviors while they snacked and played at age 13 months. They then evaluated the children's mental and motor development at age 2.

Overall, there was no statistically significant difference between the groups in the level and types of rhythmic behaviors, the researchers report in the January issue of the Journal of the American Academy of Child and Adolescent Psychiatry.

"The central hypothesis of this study, that children born prematurely would differ from control children in the type and frequency of their rhythmic behaviors, was largely unconfirmed," Unis and his colleagues conclude.

The researchers did detect some differences, but not the ones they expected. For instance, boys who had higher levels of rhythmic behaviors while snacking tended to have higher mental development scores at age 2, the report indicates. The researchers did not observe the same link in girls. But both boys and girls who exhibited lower levels of rhythmic behavior while playing on their own were more likely to have a higher mental development score at age 2.

Why less rhythmic behavior during one activity but more during another are both associated with higher development scores may not seem to make much sense, but Unis and his colleagues offer a few possible explanations. Children who show more rhythmic behavior while snacking may be trying to communicate, the authors suggest. For example, a child may point repeatedly to food that is out of reach.

In contrast, a child who is developmentally delayed might bang on a play phone rather than pretend to talk on it. As for the differences between boys and girls, the results "are an indication that girls and boys develop cognitively through different pathways," according to the researchers.

SOURCE: Journal of the American Academy of Child and Adolescent Psychiatry 2002;41:67-74.
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