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In what he describes as "the most exciting" results of his 30 years of research on shyness, Starch Professor of Psychology Jerome Kagan has released findings suggesting that the tendency for shyness is an inherited biological trait that can be detected in infants as young as four months of age.
One of the most significant discoveries of Kagan's work is that shyness in children is a non-deterministic character trait. Kagan, who is the chair of the Psychology Department, found that inherited shyness may be alleviated in the childhood years by environmental factors, but that uninhibited children were less likely to show behavioral changes.
Professor of Education Howard E. Gardner '65 agreed with this finding, saying, "If we put shy children in an environment where a set behavior can be transformed early, shyness can be attenuated. No one is marked at birth."
Half of the children that were inhibited at four months showed the same characteristics of shyness when they started school, and only a quarter will carry the behavioral characteristic into adulthood. The remaining three-quarters of the children who were originally shy will not be excessively introverted in adulthood, Kagan said.
Children who show early signs of being uninhibited carry the same behavioral trait more consistently through their lives. Kagan reports that 30 percent of the children he studied showed an early tendency toward extroversion. At four months of age, these children were not highly reactive to stimuli and exhibited "low crying."
Over 90 percent of these children will retain characteristics of fearlessness at ages two and three, over 80 percent will still be uninhibited at five years of age, and 70 percent will be extroverted as adults. Kagan said that the behavioral consistency of uninhibited children was due to a lack of intervention on the part of their parents. While parents of shy children place them in therapy that gradually desensitizes them to unfamiliar stimuli, the parents of bold children do not give them similar attention.
While almost half of those children tested by Kagan exhibited extreme shyness or boldness, the majority of children were somewhere in between, neither totally inhibited nor totally uninhibited.
"We must realize that there are very extreme ends of shyness, and only at the very ends is shyness resistant of change," Gardner said. "Most of us are in the middle. Furthermore, there are contrasting effects within a family. Thus, a bolder child is more likely to develop in the presence of a shy sibling."
Kagan has developed a series of tests that define the physiological and psychological essence of shyness.
Kagan said that shy children, whom he terms "inhibited," and bold children, described as "uninhibited," can be distinguished by their physiological reactions to a series of previously unencountered stimuli.
For example, inhibited and uninhibited children react differently when confronted with plastic keys, a cotton swab dipped in alcohol or a tape of a woman's voice saying nonsense syllables, Kagan said.
"What we discovered after 15 years of work," Kagan said, "is that 15 percent of those children we studied inherited the biological trait of being inhibited." According to Kagan, these children were characterized, at four months of age, by being very reactive to the stimuli of his tests, crying and tensing their limbs.
Two-thirds of the children that exhibited an early tendency of shyness carried this tendency to the age of two years, showing "high motor activity to stimuli." According to Kagan, these children will be "cautious, shy and restrained."
Kagan began studying psychological characteristics of children in the 1960s, when he gained access to a large set of psychological data on children from birth to age 15. Kagan assessed them at age 20, and the only quality that remained stable was shyness.
Kagan has incorporated some of his research into a course he currently teaches, Social Analysis 42, "Biology, Culture, and Human Development."
Kagan can foresee, in the future, his tests being applied on a wide level. "Concerned parents would take their child to the pediatrician in order to estimate the odds that he would be shy," Kagan said. However, before such a test can be administered in such a manner, it needs to be standardized, and pediatricians need to become interested in it, Kagan said.
According to Kagan, his work ushers in a new frontier in research. "There are many next steps [to my research]," he said. "There is genetics, [as well as] determining what it is that can change the disposition of a child."
Steven W. Matthysse, an associate professor of psychobiology who is pursuing genetic research related to Kagan's findings, said that Kagan's research is unique in its systematic isolation of variables related to behavioral characteristics.
Kagan's colleagues were unequivocal in lauding the significance of his work. Philip S. Holzman, Rabb professor of psychology, said, "[Kagan's work] is state of the art research with an attractive feature--it effectively bridges the domains of behavior and physiology."
"In that sense, [this research] has an important statement to make on the mind-body problem," Holzman said. "It is a major contribution to our understanding of the unfolding of human development."
"What is remarkable is the connection between a psychological trait and the autonomic nervous system that Professor Kagan has uncovered," Matthysse said. "Before, it was thought that shyness was an irreducible personality trait--no one thought that it might represent an overactive nervous system."
"Work like Kagan's suggests that a chain may be uncovered linking behavioral traits like shyness to a brain function," Matthysse said.
Gardner underscored the significance of Kagan's findings by pointing out the difficulty of isolating human behavioral characteristics. "We are not measuring atomic particles or examining generations of Drosophila," he said. "We are looking at human beings in different social contexts and the temperamental variability that results."
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