Washington ? Shyness may be inherited, a study suggests.

A shy child can learn to be more outgoing with age, but a physical reaction in the brain linked to a person’s temperament does not change, the study indicates.

The study, appearing this week in the journal Science, conducted brain scans on 22-year-olds and found that those who had been classified 20 years before as inhibited or shy children had a distinctive reaction in their brains when confronted with novel images.

People who had been judged as toddlers to be inhibited showed in the scans that a structure in their brains — called amygdala — responded much more actively to unexpected sights than did those who had been judged as children to be more outgoing, said Jerome Kagan, a researcher in the department of psychology at Harvard University.

“That is support for the notion that the reason they were shy, timid and reserved when they were 2 years old is because they had an excitable amygdala,” Kagan said. This suggests that shyness is a temperament that can be inherited, but the researcher said this temperament did not necessarily determine one’s eventual personality.

“They are now 22 years old,” Kagan said of the test subjects. “A lot of the ones who were fearful aren’t fearful anymore. They have overcome it. But the question is, did they still have a very active amygdala?”

Based on the brain scans, Kagan said, the answer is clearly yes.