The new mother from rural Vermont noticed that her toddler’s behavior didn’t seem to fit the descriptions in the child-rearing books. Her daughter would burst into tears when she heard a loud noise or if she wore scratchy clothes. She always demanded to be carried by her mother and never left alone.

The mother worried that there might be something wrong. Then she came across a book that described what psychologists increasingly call “the highly sensitive child.”

“The description fit perfectly. It helped me to realize that things are going to be a little different with her and I need to accept that,” she said.

Sensitive children are keen observers of the world, but tend to get overstimulated. They often live intense inner lives and are highly creative, but they are wary of new situations and of people they don’t know.

They also easily intuit the moods of others. This empathy draws their peers and sometimes even adults to confide in sensitive children. Later in life, they often go into helping professions like health care and counseling.

Roughly 1 in 5 children are highly sensitive, according to the research psychologist Elaine Aron, whose 1996 book “The Highly Sensitive Person” popularized the term.

Sensitivity is an inborn temperament, she says, that comes hard-wired and remains with people for their whole lives. Michael Pluess, a professor of developmental psychology at Queen Mary University of London, has found that our life experiences, particularly those early in life, also have a big impact.

“We found that about 50 percent of differences in sensitivity between people are due to genetic factors, the other half by environment, including the prenatal environment,” Pluess said.

He said people fall roughly into three groups: highly sensitive, whom he calls “orchids,” which need very particular environments to thrive; hardy “dandelions,” which can grow virtually anywhere; and a middle group — the largest — “tulips,” which fall somewhere between the two extremes.

He has found that highly sensitive people benefit more than less sensitive people from positive experiences. And that they are also more easily traumatized by painful experiences as children.

Tracy Cooper, a researcher at Baker University in Baldwin City, Kan., who identifies as a highly sensitive person, says the brains of such people have unique characteristics. Brain imaging studies have shown that they “have higher levels of activity in the mirror neurons, which has to do with empathy and socialization, and there is more connectivity across different segments of the brain, which informs creativity,” he said.

Their emotional openness can make highly sensitive children want to escape from feeling overwhelmed at parties and family gatherings. They can also have trouble adjusting to the bustle of the classroom.

Sensitivity is also sometimes confused with being shy. While the majority of highly sensitive children are introverts, roughly 30% are extroverts, despite their tendency to get easily overstimulated in social situations.

When Dr. Judith Orloff, a clinical psychiatrist at the University of California, Los Angeles, was growing up, she couldn’t go into shopping malls or crowded places without leaving feeling anxious or depressed. Adults told her to “toughen up.”

It was the wrong advice, she says. Sometimes you simply need to remove sensitive children from situations that distress them, she said: “Help them accept their beautiful abilities and not to be overstimulated, rather than suppressing their traits with antidepressants or anti-anxiety drugs.”

Alane Freund, a family therapist in San Rafael, Calif., has pioneered a form of equine-assisted therapy to help highly sensitive teenagers better appreciate their own traits.

Like horses, highly sensitive children will tend to enter new situations more slowly. “Horses model for the children that caution is healthy,” Freund said. “You don’t know these people, you’ve got to get the lay of the land first.”