When the third-grade teacher noticed a student habitually touching her genitals as she sat in class, she became concerned and did what Federal law requires of teachers: she told the school authorities that the girl displayed one of the signs of sexual abuse.

As it turned out, the behavior of the girl was not due to sexual abuse but rather to a childish obliviousness to self-control, said Dr. William Freidrich, a psychologist at the Mayo Clinic in Rochester, Minn., who was called in to interview the girl and her family about 18 months ago. "The girl was fine," he said.

But this experience and others like it underscore the difficulty that parents, teachers and many doctors have in discerning the line between normal and abnormal sexual behavior in children. So Dr. Friedrich and colleagues at the Mayo Clinic and in private practice in Malibu, California, set out to define the boundary by conducting the largest, most comprehensive study of sexual behavior in children. Their findings appear in the current issue of the electronic version of the Journal of Pediatrics.

For decades, child-care authorities, including Dr. Benjamin Spock, have reassured parents that occasional masturbation and exhibitionism were normal in young children. But in the last decade, evidence has mounted that engaging in certain sexual behavior often indicates that a child has been sexually abused.

"The growing awareness of sexual abuse has caused us to re-examine what's normal and what's not normal," said Dr. Carolyn M. Newberger, an assistant clinical professor of psychology at Harvard Medical School who counsels and researches sexually abused children. "This paper shows us scientifically."

Other doctors welcomed the information. " Parents often ask pediatricians about their children's sexual exploration, curiosity and other behavior," said Dr. Daniel B. Kessler, director of developmental and behavioral pediatrics at the children's health center of St. Joseph's Hospital in Phoenix. "But often pediatricians don't know what to say because there's little normative data. Now pediatricians are in a better position to say that a behavior is something we see in a lot of children and is not alarming by itself."

For a study, Dr. Friedrich and his colleagues interviewed the mothers of 1,114 children from 2 to 12 years old in Minnesota and Los Angeles County. The researchers asked how often their children displayed one of 38 kinds of sexual behavior in the previous six months, like masturbation, showing their genitals to adults and trying to see or touch other people's genitals. The responses were broken down by each child's age and sex. Psychological screens were used to determine that none of the children had been sexually abused. Thus behaviors that were reported by a significant number of mothers — 20 percent or more — were deemed normal.

Sexual behavior was most often observed among the youngest children, those 2 to 5 years old. The most prevalent behaviors included masturbating, touching the mother's or other women's breast and trying to see other people nude or undressing. Dr. Friedrich attributes these behaviors to the children's natural curiosity about the human body at a time when they are developing an awareness of their own sex and the differences between boys and girls.

Observed sexual behaviors decreased after 5, when children normally become more modest and display better self-control, Dr. Friedrich said. Among children 6 to 9, the only behaviors seen often enough to be considered normal were touching private parts when at home and trying to look at other people when they are nude or undressing. And the only sexual behavior displayed by a significant number of 10 to 12 year-olds was an interest in the opposite sex.

For each age group, a number of sexual behaviors were reported by fewer than 20 percent of mothers. They included children's touching other children's sex parts, making sexual sounds, kissing or hugging adults not known well or asking others to perform sex acts. But Dr. Friedrich cautioned that the study offered general, not rigid guidelines on which behaviors were normal.

Each case of unusual behavior must be seen in context, Dr. Friedrich said. A child who exhibits one of the unusual behaviors just once or twice is not a cause for concern. But if the behavior occurs frequently and persists even when parents or other care givers tell the child to stop, it could be a sign of sexual abuse or other problems, like exposure to violence, Dr. Friedrich said. By the same token, he said, a behavior that is generally considered normal may indicate one of these problems in a child who engages in it frequently.

The study did not address just when an abnormal behavior signals a serious problem. But parents, teachers and doctors need to know in order to understand whether a child's sexual behavior is within normal limits, said Dr. David E. Sandberg, a psychologist at the State University of New York at Buffalo who specializes in children's sexual disorders.

"This study is a good first step," he said. "But it would be helpful to know if there is a cutoff of the incidence of sexual behaviors that would indicate that an in-depth evaluation by a mental health professional is needed."

Reprinted by permission of The New York Times, Inc., appeared 4/7/98.

Originally published in the 1998 Fall issue of The CampLine.